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Before 1973

Polar bears are an integral part of the Arctic ecosystem and the food web for Indigenous Peoples - who have hunted polar bears sustainably for millennia. But, beginning in the 1700s, large-scale hunting by European, Russian and North American hunters and trappers took place, raising concerns about the future survival of polar bears. Unregulated commercial and recreational hunting continued until the 1970s.

1973

Canada, the United States, Denmark, Norway and the former USSR signed the International Agreement on the Conservation of Polar Bears and their Habitat, strictly regulating commercial hunting.

The US Government classified the Polar Bear under its Endangered Species Act (ESA).
2005
The polar bear was upgraded from Least Concern to Vulnerable by the the IUCN Polar Bear Specialist Group.
2013
Ministers and other leaders from the five polar bear range states met in Moscow for the first International Forum on Polar Bear Conservation. The leaders made significant commitments to address issues of polar bear habitat, research and trade. This event was supported by WWF.

Today

Today, polar bears are among the few large carnivores that are still found in roughly their original habitat and range-and in some places, in roughly their natural numbers.

Although most of the world's 19 populations have returned to healthy numbers, there are differences between them. Some are stable, some seem to be increasing, and some are decreasing due to various pressures.

Status of the polar bear populations
Updated 2021 with data from the IUCN Polar Bear Specialists Group:

3 populations are in decline
2 populations are increasing
4 populations are stable
10 populations are data-deficient (information missing or outdated)

In the future

By 2040, scientists predict that only a fringe of ice will remain in Northeast Canada and Northern Greenland when all other large areas of summer ice are gone. This "Last Ice Area" is likely to become important for polar bears and other life that depends on ice.

A projection of sea ice in the archipelago, supported by WWF, shows that much of the region is facing significant ice loss in the coming decades - with potentially serious consequences for polar bears.
Global polar bear numbers are projected to decline by 30% by 2050.

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How many polar bears are there? See current polar bear populations, IUCN Red List status by country and timeline of polar bear conservation.

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https://climate.nasa.gov/vital-signs/sea-level/

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Climate Change: Vital Signs of the Planet

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101 (± 4.0) mm

This is the "uncertainty margin," or the range from the mean (average) within which there is a high probability that the true number resides. For example, when we say global sea level has risen 101 mm +/- 4 mm, the true value has a high probability of being between 97 and 105 mm. The uncertainty margin exists both because of sea level variability (sea level above the first point in the time series) in the ocean and the accuracy with which we measure the individual values.

Key Takeaway:

Global sea levels are rising as a result of human-caused global warming, with recent rates being unprecedented over the past 2,500-plus years.

Sea level rise is caused primarily by two factors related to global warming: the added water from melting ice sheets and glaciers, and the expansion of seawater as it warms. The first graph tracks the change in global sea level since 1993, as observed by satellites.

The second graph, which is from coastal tide gauge and satellite data, shows how much sea level changed from about 1900 to 2018. Items with pluses (+) are factors that cause global sea level to increase, while minuses (-) are what cause sea level to decrease. These items are displayed at the time they were affecting sea level.

The data shown are the latest available, with a four- to five-month delay needed for processing.

* You now need to create an Earthdata account to access NASA's sea level data. Register here for free. Once logged in, click the "download data" button on this page to access the data.
NASA Sea Level Change

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Vital Signs of the Planet: Global Climate Change and Global Warming. Current news and data streams about global warming and climate change from NASA.

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https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide

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Based on the annual report from NOAA's Global Monitoring Lab, global average atmospheric carbon dioxide was 417.06 parts per million ("ppm" for short) in 2022, setting a new record high. The increase between 2021 and 2022 was 2.13 ppm-the 11 th year in a row where the amount of carbon dioxide in the atmosphere increased by more than 2 ppm. At Mauna Loa Observatory in Hawaii, where the modern carbon dioxide record began in 1958, the annual average carbon dioxide in 2022 was 418.56.

Carbon dioxide concentrations are rising mostly because of the fossil fuels that people are burning for energy. Fossil fuels like coal and oil contain carbon that plants pulled out of the atmosphere through photosynthesis over many millions of years; we are returning that carbon to the atmosphere in just a few hundred. Since the middle of the 20 th century, annual emissions from burning fossil fuels have increased every decade, from close to 11 billion tons of carbon dioxide per year in the 1960s to an estimated 36.6 billion tons in 2022 according to the Global Carbon Budget 2022.

Carbon cycle experts estimate that natural "sinks"-processes that remove carbon from the atmosphere-on land and in the ocean absorbed the equivalent of about half of the carbon dioxide we emitted each year in the 2011-2020 decade. Because we put more carbon dioxide into the atmosphere than natural sinks can remove, the total amount of carbon dioxide in the atmosphere increases every year.

The more we overshoot what natural processes can remove in a given year, the faster the atmospheric concentration of carbon dioxide rises. In the 1960s, the global growth rate of atmospheric carbon dioxide was roughly 0.8± 0.1 ppm per year. Over the next half century, the annual growth rate tripled, reaching 2.4 ppm per year during the 2010s. The annual rate of increase in atmospheric carbon dioxide over the past 60 years is about 100 times faster than previous natural increases, such as those that occurred at the end of the last ice age 11,000-17,000 years ago.

Why carbon dioxide matters

Carbon dioxide is Earth's most important greenhouse gas: a gas that absorbs and radiates heat. Unlike oxygen or nitrogen (which make up most of our atmosphere), greenhouse gases absorb heat radiating from the Earth's surface and re-release it in all directions-including back toward Earth's surface. Without carbon dioxide, Earth's natural greenhouse effect would be too weak to keep the average global surface temperature above freezing. By adding more carbon dioxide to the atmosphere, people are supercharging the natural greenhouse effect, causing global temperature to rise. According to observations by the NOAA Global Monitoring Lab, in 2021 carbon dioxide alone was responsible for about two-thirds of the total heating influence of all human-produced greenhouse gases.

Another reason carbon dioxide is important in the Earth system is that it dissolves into the ocean like the fizz in a can of soda. It reacts with water molecules, producing carbonic acid and lowering the ocean's pH (raising its acidity). Since the start of the Industrial Revolution, the pH of the ocean's surface waters has dropped from 8.21 to 8.10. This drop in pH is called ocean acidification.

Past and future carbon dioxide

Natural increases in carbon dioxide concentrations have periodically warmed Earth's temperature during ice age cycles over the past million years or more. The warm episodes (interglacials) began with a small increase in incoming sunlight in the Northern Hemisphere due to variations in Earth's orbit around the Sun and its axis of rotation. (For more details, see the "Milankovitch cycles and ice ages" section of our Climate change: incoming sunlight article.) That little bit of extra sunlight caused a little bit of warming. As the oceans warmed, they outgassed carbon dioxide-like a can of soda going flat in the heat of a summer day. The extra carbon dioxide in the atmosphere greatly amplified the initial, solar-driven warming.

Based on air bubbles trapped in mile-thick ice cores and other paleoclimate evidence, we know that during the ice age cycles of the past million years or so, atmospheric carbon dioxide never exceeded 300 ppm. Before the Industrial Revolution started in the mid-1700s, atmospheric carbon dioxide was 280 ppm or less.

By the time continuous observations began at Mauna Loa Volcanic Observatory in 1958, global atmospheric carbon dioxide was already 315 ppm. Carbon dioxide levels today are higher than at any point in human history. In fact, the last time atmospheric carbon dioxide amounts were this high was more than 3 million years ago, during the Mid-Pliocene Warm Period, when global surface temperature was 4.5-7.2 degrees Fahrenheit (2.5-4 degrees Celsius) warmer than during the pre-industrial era. Sea level was at least 16 feet higher than it was in 1900 and possibly as much as 82 feet higher.

If global energy demand continues to grow rapidly and we meet it mostly with fossil fuels, human emissions of carbon dioxide could reach 75 billion tons per year or more by the end of the century. Atmospheric carbon dioxide could be 800 ppm or higher-conditions not seen on Earth for close to 50 million years.

More on carbon dioxide
NOAA carbon dioxide observations Carbon cycle factsheet Carbon dioxide emissions by country over time Comparing greenhouse gases by their global warming potential Ocean acidification
References

Collins, M., R. Knutti, J. Arblaster, J.-L. Dufresne, T. Fichefet, P. Friedlingstein, X. Gao, W.J. Gutowski, T. Johns, G. Krinner, M. Shongwe, C. Tebaldi, A.J. Weaver and M. Wehner, 2013: Long-term Climate Change: Projections, Commitments and Irreversibility. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Friedlingstein, P., O'Sullivan, M., Jones, M. W., Andrew, R. M., Gregor, L., Hauck, J., Le Quéré, C., Luijkx, I. T., Olsen, A., Peters, G. P., Peters, W., Pongratz, J., Schwingshackl, C., Sitch, S., Canadell, J. G., Ciais, P., Jackson, R. B., Alin, S. R., Alkama, R., ... Zheng, B. (2022). Global Carbon Budget 2022. Earth System Science Data, 14(11), 4811-4900. https://doi.org/10.5194/essd-14-4811-2022

Lan, X., B. D. Hall, G. Dutton, J. Mühle, J. W. Elkins, and I. J. Vimont. (2022). Long-lived greenhouses gases [in State of the Climate in 2021, Chapter 2: Global Climate]. Bulletin of the American Meteorological Society, 103 (8), S81-S84. https://doi.org/10.1175/BAMS-D-22-0092.1.

Lüthi, D., M. Le Floch, B. Bereiter, T. Blunier, J.-M. Barnola, U. Siegenthaler, D. Raynaud, J. Jouzel, H. Fischer, K. Kawamura, and T.F. Stocker. (2008). High-resolution carbon dioxide concentration record 650,000-800,000 years before present. Nature, Vol. 453, pp. 379-382. doi:10.1038/nature06949.

Woods Hole Oceanographic Institution. (2015). Introduction to ocean acidification. Accessed October 4, 2017.

Lindsey, R. (2009). Climate and Earth's energy budget. Accessed October 4, 2017.

Based on the annual report from NOAA's Global Monitoring Lab, global average atmospheric carbon dioxide was 417.06 parts per million ("ppm" for short) in 2022, setting a new record high. The increase between 2021 and 2022 was 2.13 ppm-the 11 th year in a row where the amount of carbon dioxide in the atmosphere increased by more than 2 ppm. At Mauna Loa Observatory in Hawaii, where the modern carbon dioxide record began in 1958, the annual average carbon dioxide in 2022 was 418.56.

Carbon dioxide concentrations are rising mostly because of the fossil fuels that people are burning for energy. Fossil fuels like coal and oil contain carbon that plants pulled out of the atmosphere through photosynthesis over many millions of years; we are returning that carbon to the atmosphere in just a few hundred. Since the middle of the 20 th century, annual emissions from burning fossil fuels have increased every decade, from close to 11 billion tons of carbon dioxide per year in the 1960s to an estimated 36.6 billion tons in 2022 according to the Global Carbon Budget 2022.

Carbon cycle experts estimate that natural "sinks"-processes that remove carbon from the atmosphere-on land and in the ocean absorbed the equivalent of about half of the carbon dioxide we emitted each year in the 2011-2020 decade. Because we put more carbon dioxide into the atmosphere than natural sinks can remove, the total amount of carbon dioxide in the atmosphere increases every year.

The more we overshoot what natural processes can remove in a given year, the faster the atmospheric concentration of carbon dioxide rises. In the 1960s, the global growth rate of atmospheric carbon dioxide was roughly 0.8± 0.1 ppm per year. Over the next half century, the annual growth rate tripled, reaching 2.4 ppm per year during the 2010s. The annual rate of increase in atmospheric carbon dioxide over the past 60 years is about 100 times faster than previous natural increases, such as those that occurred at the end of the last ice age 11,000-17,000 years ago.

Why carbon dioxide matters

Carbon dioxide is Earth's most important greenhouse gas: a gas that absorbs and radiates heat. Unlike oxygen or nitrogen (which make up most of our atmosphere), greenhouse gases absorb heat radiating from the Earth's surface and re-release it in all directions-including back toward Earth's surface. Without carbon dioxide, Earth's natural greenhouse effect would be too weak to keep the average global surface temperature above freezing. By adding more carbon dioxide to the atmosphere, people are supercharging the natural greenhouse effect, causing global temperature to rise. According to observations by the NOAA Global Monitoring Lab, in 2021 carbon dioxide alone was responsible for about two-thirds of the total heating influence of all human-produced greenhouse gases.

Another reason carbon dioxide is important in the Earth system is that it dissolves into the ocean like the fizz in a can of soda. It reacts with water molecules, producing carbonic acid and lowering the ocean's pH (raising its acidity). Since the start of the Industrial Revolution, the pH of the ocean's surface waters has dropped from 8.21 to 8.10. This drop in pH is called ocean acidification.

Past and future carbon dioxide

Natural increases in carbon dioxide concentrations have periodically warmed Earth's temperature during ice age cycles over the past million years or more. The warm episodes (interglacials) began with a small increase in incoming sunlight in the Northern Hemisphere due to variations in Earth's orbit around the Sun and its axis of rotation. (For more details, see the "Milankovitch cycles and ice ages" section of our Climate change: incoming sunlight article.) That little bit of extra sunlight caused a little bit of warming. As the oceans warmed, they outgassed carbon dioxide-like a can of soda going flat in the heat of a summer day. The extra carbon dioxide in the atmosphere greatly amplified the initial, solar-driven warming.

Based on air bubbles trapped in mile-thick ice cores and other paleoclimate evidence, we know that during the ice age cycles of the past million years or so, atmospheric carbon dioxide never exceeded 300 ppm. Before the Industrial Revolution started in the mid-1700s, atmospheric carbon dioxide was 280 ppm or less.

By the time continuous observations began at Mauna Loa Volcanic Observatory in 1958, global atmospheric carbon dioxide was already 315 ppm. Carbon dioxide levels today are higher than at any point in human history. In fact, the last time atmospheric carbon dioxide amounts were this high was more than 3 million years ago, during the Mid-Pliocene Warm Period, when global surface temperature was 4.5-7.2 degrees Fahrenheit (2.5-4 degrees Celsius) warmer than during the pre-industrial era. Sea level was at least 16 feet higher than it was in 1900 and possibly as much as 82 feet higher.

If global energy demand continues to grow rapidly and we meet it mostly with fossil fuels, human emissions of carbon dioxide could reach 75 billion tons per year or more by the end of the century. Atmospheric carbon dioxide could be 800 ppm or higher-conditions not seen on Earth for close to 50 million years.

More on carbon dioxide
NOAA carbon dioxide observations Carbon cycle factsheet Carbon dioxide emissions by country over time Comparing greenhouse gases by their global warming potential Ocean acidification
References

Collins, M., R. Knutti, J. Arblaster, J.-L. Dufresne, T. Fichefet, P. Friedlingstein, X. Gao, W.J. Gutowski, T. Johns, G. Krinner, M. Shongwe, C. Tebaldi, A.J. Weaver and M. Wehner, 2013: Long-term Climate Change: Projections, Commitments and Irreversibility. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Friedlingstein, P., O'Sullivan, M., Jones, M. W., Andrew, R. M., Gregor, L., Hauck, J., Le Quéré, C., Luijkx, I. T., Olsen, A., Peters, G. P., Peters, W., Pongratz, J., Schwingshackl, C., Sitch, S., Canadell, J. G., Ciais, P., Jackson, R. B., Alin, S. R., Alkama, R., ... Zheng, B. (2022). Global Carbon Budget 2022. Earth System Science Data, 14(11), 4811-4900. https://doi.org/10.5194/essd-14-4811-2022

Lan, X., B. D. Hall, G. Dutton, J. Mühle, J. W. Elkins, and I. J. Vimont. (2022). Long-lived greenhouses gases [in State of the Climate in 2021, Chapter 2: Global Climate]. Bulletin of the American Meteorological Society, 103 (8), S81-S84. https://doi.org/10.1175/BAMS-D-22-0092.1.

Lüthi, D., M. Le Floch, B. Bereiter, T. Blunier, J.-M. Barnola, U. Siegenthaler, D. Raynaud, J. Jouzel, H. Fischer, K. Kawamura, and T.F. Stocker. (2008). High-resolution carbon dioxide concentration record 650,000-800,000 years before present. Nature, Vol. 453, pp. 379-382. doi:10.1038/nature06949.

Woods Hole Oceanographic Institution. (2015). Introduction to ocean acidification. Accessed October 4, 2017.

Lindsey, R. (2009). Climate and Earth's energy budget. Accessed October 4, 2017.

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Climate Change: Atmospheric Carbon Dioxide

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In the past 60 years, carbon dioxide in the atmosphere has increased 100 times faster than it did during the end of the last ice age.

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https://www.arcticwwf.org/wildlife/polar-bear/polar-bear-population/

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https://en.m.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_atmosphere

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 나혜령 윤하연 이채경

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 나혜령 윤하연 이채경

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https://www.arcticwwf.org/wildlife/polar-bear/polar-bear-population/

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이승빈,손예찬,이지오ㆍ

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In common usage, climate change describes global warming-the ongoing increase in global average temperature-and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to Earth's climate. The current rise in global average temperature is more rapid than previous changes, and is primarily caused by humans burning fossil fuels.[2][3] Fossil fuel use, deforestation, and some agricultural and industrial practices add to greenhouse gases, notably carbon dioxide and methane.[4] Greenhouse gases absorb some of the heat that the Earth radiates after it warms from sunlight. Larger amounts of these gases trap more heat in Earth's lower atmosphere, causing global warming.

Average surface air temperatures 2011-21 compared to 1956-76

Change in average surface air temperature since the Industrial Revolution, plus drivers for that change. Human activity has caused increased temperatures, with natural forces adding some variability.[1]

Climate change is causing a range of increasing impacts on the environment. Deserts are expanding, while heat waves and wildfires are becoming more common.[5] Amplified warming in the Arctic has contributed to melting permafrost, glacial retreat and sea ice loss.[6] Higher temperatures are also causing more intense storms, droughts, and other weather extremes.[7] Rapid environmental change in mountains, coral reefs, and the Arctic is forcing many species to relocate or become extinct.[8] Even if efforts to minimise future warming are successful, some effects will continue for centuries. These include ocean heating, ocean acidification and sea level rise.[9]

Climate change threatens people with increased flooding, extreme heat, increased food and water scarcity, more disease, and economic loss. Human migration and conflict can also be a result.[10] The World Health Organization (WHO) calls climate change the greatest threat to global health in the 21st century.[11] Adapting to climate change through efforts like flood control measures or drought-resistant crops partially reduces climate change risks, although some limits to adaptation have already been reached.[12] Poorer communities are responsible for a small share of global emissions, yet have the least ability to adapt and are most vulnerable to climate change.[13][14] The expense, time required, and limits of adaptation mean its success hinges on limiting global warming.[15]

Many climate change impacts are already felt at the current 1.2 °C (2.2 °F) level of warming. Additional warming will increase these impacts and can trigger tipping points, such as the melting of the Greenland ice sheet.[17] Under the 2015 Paris Agreement, nations collectively agreed to keep warming "well under 2 °C". However, with pledges made under the Agreement, global warming would still reach about 2.7 °C (4.9 °F) by the end of the century.[18] Limiting warming to 1.5 °C will require halving emissions by 2030 and achieving net-zero emissions by 2050.[19]

Reducing emissions requires reducing energy use and generating electricity from low-carbon sources rather than burning fossil fuels. This change includes phasing out coal and natural gas fired power plants while vastly increasing electricity generated from wind, solar, and nuclear power. This electricity will need to replace fossil fuels for powering transportation, heating buildings, and operating industrial facilities.[20][21] Carbon can also be removed from the atmosphere, for instance by increasing forest cover and farming with methods that capture carbon in soil.[22]

There has been an increase in the ocean heat content during recent decades as the oceans absorb over 90% of the heat from global warming.[31]

Multiple independent instrumental datasets show that the climate system is warming.[32] A so-called "global warming hiatus" from 1998 to 2013 when warming was relatively slow was likely caused by negative phases of the Pacific Decadal Oscillation (PDO)[33] and Atlantic Multidecadal Oscillation (AMO).[34] The 2011-2020 decade warmed to an average 1.09 °C [0.95-1.20 °C] compared to the pre-industrial baseline (1850-1900).[35] Surface temperatures are rising by about 0.2 °C per decade,[36] with 2020 reaching a temperature of 1.2 °C above the pre-industrial era. Since 1950, the number of cold days and nights has decreased, and the number of warm days and nights has increased.[38]

Evidence of warming from air temperature measurements is reinforced by a wide range of other observations.[39] For example, changes to the natural water cycle have been predicted and observed, such as an increase in the frequency and intensity of heavy precipitation, melting of snow and land ice, and increased atmospheric humidity.[41] Flora and fauna are also behaving in a manner consistent with warming; for instance, plants are flowering earlier in spring.[42] Another key indicator is the cooling of the upper atmosphere, which demonstrates that greenhouse gases are trapping heat near the Earth's surface and preventing it from radiating into space.[43]

Different regions of the world warm at different rates. The pattern is independent of where greenhouse gases are emitted, because the gases persist long enough to diffuse across the planet. Since the pre-industrial period, the average surface temperature over land regions has increased almost twice as fast as the global-average surface temperature.[44] This is because of the larger heat capacity of oceans, and because oceans lose more heat by evaporation.[45] The thermal energy in the global climate system has grown with only brief pauses since at least 1970, and over 90% of this extra energy has been stored in the ocean.[46][47] The rest has heated the atmosphere, melted ice, and warmed the continents.[48]

The Northern Hemisphere and the North Pole have warmed much faster than the South Pole and Southern Hemisphere. The Northern Hemisphere not only has much more land, but also more seasonal snow cover and sea ice. As these surfaces flip from reflecting a lot of light to being dark after the ice has melted, they start absorbing more heat.[49] Local black carbon deposits on snow and ice also contribute to Arctic warming.[50] Arctic temperatures are increasing at over twice the rate of the rest of the world.[51] Melting of glaciers and ice sheets in the Arctic disrupts ocean circulation, including a weakened Gulf Stream, further changing the climate.[52]

Temperature records prior to global warming

Global surface temperature reconstruction over the last 2000 years using proxy data from tree rings, corals, and ice cores in blue.[53] Directly observed data is in red.[54]

Human beings evolved over the last few million years in a climate that cycled through ice ages, with global average temperature ranging between current levels and 5-6 °C colder than today.[55][56] The temperature record prior to human evolution includes hotter temperatures and occasional abrupt changes, such as the Paleocene-Eocene Thermal Maximum 55.5 million years ago.[57]

Historical patterns of warming and cooling, like the Medieval Warm Period and the Little Ice Age, did not occur at the same time across different regions. Temperatures may have reached as high as those of the late 20th century in a limited set of regions.[58]

There was little net warming between the 18th century and the mid-19th century. Climate information for that period comes from climate proxies, such as trees and ice cores.[59] Thermometer records began to provide global coverage around 1850.[60]

Drivers of climate change from 1850-1900 to 2010-2019. There was no significant contribution from internal variability or solar and volcanic drivers.

The climate system experiences various cycles on its own which can last for years (such as the El Niño-Southern Oscillation (ENSO)), decades or even centuries.[61] Other changes are caused by an imbalance of energy that is "external" to the climate system, but not always external to the Earth.[62] Examples of external forcings include changes in the concentrations of greenhouse gases, solar luminosity, volcanic eruptions, and variations in the Earth's orbit around the Sun.[63]

To determine the human contribution to climate change, known internal climate variability and natural external forcings are ruled out. Unique "fingerprints" for all potential causes are determined and compared with observed patterns of climate change.[64] For example, solar forcing-whose fingerprint involves warming the entire atmosphere-is ruled out because only the lower atmosphere has warmed.[65] Attribution of recent climate change shows that the climate's main driver is elevated greenhouse gases, with aerosols having a dampening effect.[66]

Greenhouse gases

CO₂ concentrations over the last 800,000 years as measured from ice cores[67][68][69][70] (blue/green) and directly[71] (black)

Greenhouse gases are transparent to sunlight, and thus allow it to pass through the atmosphere to heat the Earth's surface. The Earth radiates it as heat, and greenhouse gases absorb a portion of it. This absorption slows the rate at which heat escapes into space, trapping heat near the Earth's surface and warming it over time.[72] Before the Industrial Revolution, naturally-occurring amounts of greenhouse gases caused the air near the surface to be about 33 °C warmer than it would have been in their absence.[73][74] While water vapour (≈50%) and clouds (≈25%) are the biggest contributors to the greenhouse effect, they increase as a function of temperature and are therefore feedbacks. On the other hand, concentrations of gases such as CO ₂ (≈20%), tropospheric ozone,[75] CFCs and nitrous oxide are not temperature-dependent, and are therefore external forcings.[76]

Human activity since the Industrial Revolution, mainly extracting and burning fossil fuels ( coal, oil, and natural gas),[77] has increased the amount of greenhouse gases in the atmosphere, resulting in a radiative imbalance. In 2019, the concentrations of CO₂ and methane had increased by about 48% and 160%, respectively, since 1750.[78] These CO ₂ levels are higher than they have been at any time during the last 2 million years. Concentrations of methane are far higher than they were over the last 800,000 years.

The Global Carbon Project shows how additions to CO₂ since 1880 have been caused by different sources ramping up one after another.

Global anthropogenic greenhouse gas emissions in 2019 were equivalent to 59 billion tonnes of CO ₂. Of these emissions, 75% was CO ₂, 18% was methane, 4% was nitrous oxide, and 2% was fluorinated gases. CO ₂ emissions primarily come from burning fossil fuels to provide energy for transport, manufacturing, heating, and electricity.[4] Additional CO ₂ emissions come from deforestation and industrial processes, which include the CO ₂ released by the chemical reactions for making cement, steel, aluminum, and fertiliser.[81] Methane emissions come from livestock, manure, rice cultivation, landfills, wastewater, and coal mining, as well as oil and gas extraction.[82] Nitrous oxide emissions largely come from the microbial decomposition of fertiliser.[83]

Despite the contribution of deforestation to greenhouse gas emissions, the Earth's land surface, particularly its forests, remain a significant carbon sink for CO ₂. Land-surface sink processes, such as carbon fixation in the soil and photosynthesis, remove about 29% of annual global CO ₂ emissions.[84] The ocean also serves as a significant carbon sink via a two-step process. First, CO ₂ dissolves in the surface water. Afterwards, the ocean's overturning circulation distributes it deep into the ocean's interior, where it accumulates over time as part of the carbon cycle. Over the last two decades, the world's oceans have absorbed 20 to 30% of emitted CO ₂.[85]

Aerosols and clouds

Air pollution, in the form of aerosols, affects the climate on a large scale.[86] Aerosols scatter and absorb solar radiation. From 1961 to 1990, a gradual reduction in the amount of sunlight reaching the Earth's surface was observed. This phenomenon is popularly known as global dimming,[87] and is attributed to aerosols produced by dust, pollution and combustion of biofuels and fossil fuels.[88][89][90][91][92] Globally, aerosols have been declining since 1990 due to pollution controls, meaning that they no longer mask greenhouse gas warming as much.[93]

Aerosols also have indirect effects on the Earth's radiation budget. Sulfate aerosols act as cloud condensation nuclei and lead to clouds that have more and smaller cloud droplets. These clouds reflect solar radiation more efficiently than clouds with fewer and larger droplets.[94] They also reduce the growth of raindrops, which makes clouds more reflective to incoming sunlight.[95] Indirect effects of aerosols are the largest uncertainty in radiative forcing.[96]

While aerosols typically limit global warming by reflecting sunlight, black carbon in soot that falls on snow or ice can contribute to global warming. Not only does this increase the absorption of sunlight, it also increases melting and sea-level rise.[97] Limiting new black carbon deposits in the Arctic could reduce global warming by 0.2 °C by 2050.[98]

Land surface changes

Humans change the Earth's surface mainly to create more agricultural land. Today, agriculture takes up 34% of Earth's land area, while 26% is forests, and 30% is uninhabitable (glaciers, deserts, etc.).[100] The amount of forested land continues to decrease, which is the main land use change that causes global warming.[101] Deforestation releases CO ₂ contained in trees when they are destroyed, plus it prevents those trees from absorbing more CO ₂.[22] The main causes of deforestation are: permanent land-use change from forest to agricultural land producing products such as beef and palm oil (27%), logging to produce forestry/forest products (26%), short term shifting cultivation (24%), and wildfires (23%).[102]

The type of vegetation in a region affects the local temperature. It impacts how much of the sunlight gets reflected back into space ( albedo), and how much heat is lost by evaporation. For instance, the change from a dark forest to grassland makes the surface lighter, causing it to reflect more sunlight. Deforestation can also affect temperatures by modifying the release of chemical compounds that influence clouds, and by changing wind patterns.[103] In tropic and temperate areas the net effect is to produce significant warming, while at latitudes closer to the poles a gain of albedo (as forest is replaced by snow cover) leads to a cooling effect.[103] Globally, these effects are estimated to have led to a slight cooling, dominated by an increase in surface albedo.[104] According to FAO, forest degradation aggravates the impacts of climate change as it reduces the carbon sequestration abilities of forests. Indeed, among their many benefits, forests also have the potential to reduce the impact of high temperatures.[105]

Solar and volcanic activity

As the Sun is the Earth's primary energy source, changes in incoming sunlight directly affect the climate system.[96] Solar irradiance has been measured directly by satellites,[106] and indirect measurements are available from the early 1600s onwards.[96] Since 1880, there has been no upward trend in the amount of the Sun's energy reaching the Earth.[107]

Explosive volcanic eruptions represent the largest natural forcing over the industrial era. When the eruption is sufficiently strong (with sulfur dioxide reaching the stratosphere), sunlight can be partially blocked for a couple of years. The temperature signal lasts about twice as long. In the industrial era, volcanic activity has had negligible impacts on global temperature trends.[108] Present-day volcanic CO₂ emissions are equivalent to less than 1% of current anthropogenic CO ₂ emissions.

Physical climate models are unable to reproduce the rapid warming observed in recent decades when taking into account only variations in solar output and volcanic activity.[110] Further evidence for greenhouse gases causing global warming comes from measurements that show a warming of the lower atmosphere (the troposphere), coupled with a cooling of the upper atmosphere (the stratosphere).[111] If solar variations were responsible for the observed warming, the troposphere and stratosphere would both warm.[65]

Climate change feedback

Sea ice reflects 50% to 70% of incoming sunlight, while the ocean, being darker, reflects only 6%. As an area of sea ice melts and exposes more ocean, more heat is absorbed by the ocean, raising temperatures that melt still more ice. This is a positive feedback process.[112]

The response of the climate system to an initial forcing is modified by feedbacks: increased by "self-reinforcing" or "positive" feedbacks and reduced by "balancing" or "negative" feedbacks.[113] The main reinforcing feedbacks are the water-vapour feedback, the ice-albedo feedback, and the net effect of clouds.[115] The primary balancing mechanism is radiative cooling, as Earth's surface gives off more heat to space in response to rising temperature. In addition to temperature feedbacks, there are feedbacks in the carbon cycle, such as the fertilizing effect of CO ₂ on plant growth.[117] Uncertainty over feedbacks is the major reason why different climate models project different magnitudes of warming for a given amount of emissions.[118]

As air warms, it can hold more moisture. Water vapour, as a potent greenhouse gas, holds heat in the atmosphere. If cloud cover increases, more sunlight will be reflected back into space, cooling the planet. If clouds become higher and thinner, they act as an insulator, reflecting heat from below back downwards and warming the planet. The effect of clouds is the largest source of feedback uncertainty.[120]

Another major feedback is the reduction of snow cover and sea ice in the Arctic, which reduces the reflectivity of the Earth's surface.[121] More of the Sun's energy is now absorbed in these regions, contributing to amplification of Arctic temperature changes.[122] Arctic amplification is also melting permafrost, which releases methane and CO ₂ into the atmosphere.[123] Climate change can also cause methane releases from wetlands, marine systems, and freshwater systems. Overall, climate feedbacks are expected to become increasingly positive.[125]

Around half of human-caused CO ₂ emissions have been absorbed by land plants and by the oceans.[126] Climate change increases droughts and heat waves that inhibit plant growth, which makes it uncertain whether this carbon sink will continue to grow.[127] Soils contain large quantities of carbon and may release some when they heat up.[128] As more CO ₂ and heat are absorbed by the ocean, it acidifies, its circulation changes and phytoplankton takes up less carbon, decreasing the rate at which the ocean absorbs atmospheric carbon. Overall, at higher CO ₂ concentrations the Earth will absorb a reduced fraction of our emissions.[130]

Projected global surface temperature changes relative to 1850-1900, based on CMIP6 multi-model mean changes

A climate model is a representation of the physical, chemical and biological processes that affect the climate system.[131] Models also include natural processes like changes in the Earth's orbit, historical changes in the Sun's activity, and volcanic forcing.[132] Models are used to estimate the degree of warming future emissions will cause when accounting for the strength of climate feedbacks,[133][134] or reproduce and predict the circulation of the oceans, the annual cycle of the seasons, and the flows of carbon between the land surface and the atmosphere.[135]

The physical realism of models is tested by examining their ability to simulate contemporary or past climates.[136] Past models have underestimated the rate of Arctic shrinkage[137] and underestimated the rate of precipitation increase.[138] Sea level rise since 1990 was underestimated in older models, but more recent models agree well with observations.[139] The 2017 United States-published National Climate Assessment notes that "climate models may still be underestimating or missing relevant feedback processes".[140] Additionally, climate models may be unable to adequately predict short-term regional climatic shifts.[141]

Simplified model: Energy flows between space, the atmosphere, and Earth's surface, with greenhouse gases in the atmosphere absorbing and emitting radiant heat, affecting Earth's energy balance. Data as of 2007.

A subset of climate models add societal factors to a simple physical climate model. These models simulate how population, economic growth, and energy use affect-and interact with-the physical climate. With this information, these models can produce scenarios of future greenhouse gas emissions. This is then used as input for physical climate models and carbon cycle models to predict how atmospheric concentrations of greenhouse gases might change.[142][143] Depending on the socioeconomic scenario and the mitigation scenario, models produce atmospheric CO ₂ concentrations that range widely between 380 and 1400 ppm.[144]

The IPCC Sixth Assessment Report projects that global warming is very likely to reach 1.0 °C to 1.8 °C by the late 21st century under the very low GHG emissions scenario. In an intermediate scenario global warming would reach 2.1 °C to 3.5 °C, and 3.3 °C to 5.7 °C under the very high GHG emissions scenario.[145] These projections are based on climate models in combination with observations.

The remaining carbon budget is determined by modelling the carbon cycle and the climate sensitivity to greenhouse gases.[147] According to the IPCC, global warming can be kept below 1.5 °C with a two-thirds chance if emissions after 2018 do not exceed 420 or 570 gigatonnes of CO ₂. This corresponds to 10 to 13 years of current emissions. There are high uncertainties about the budget. For instance, it may be 100 gigatonnes of CO ₂ smaller due to methane release from permafrost and wetlands.[148] However, it is clear that fossil fuel resources are too abundant for shortages to be relied on to limit carbon emissions in the 21st century.[149]

Even though the temperature will need to stay at or above 1.5 °C for 20 years to pass the threshold defined by the Paris agreement, a temporary rise above this limit also can have severe consequences. According to the World Meteorological Organization, there is a 66% chance that global temperature will rise temporarily above 1.5 °C in the years 2023-2027.[150][151]

The sixth IPCC Assessment Report projects changes in average soil moisture that can disrupt agriculture and ecosystems. A reduction in soil moisture by one standard deviation means that average soil moisture will approximately match the ninth driest year between 1850 and 1900 at that location.

Environmental effects

The environmental effects of climate change are broad and far-reaching, affecting oceans, ice, and weather. Changes may occur gradually or rapidly. Evidence for these effects comes from studying climate change in the past, from modelling, and from modern observations.[152] Since the 1950s, droughts and heat waves have appeared simultaneously with increasing frequency.[153] Extremely wet or dry events within the monsoon period have increased in India and East Asia.[154] The rainfall rate and intensity of hurricanes and typhoons is likely increasing,[155] and the geographic range likely expanding poleward in response to climate warming.[156] Frequency of tropical cyclones has not increased as a result of climate change.[157]

Global sea level is rising as a consequence of glacial melt, melt of the Greenland ice sheets and Antarctica, and thermal expansion. Between 1993 and 2020, the rise increased over time, averaging 3.3 ± 0.3 mm per year.[159] Over the 21st century, the IPCC projects that in a very high emissions scenario the sea level could rise by 61-110 cm.[160] Increased ocean warmth is undermining and threatening to unplug Antarctic glacier outlets, risking a large melt of the ice sheet[161] and the possibility of a 2-meter sea level rise by 2100 under high emissions.

Climate change has led to decades of shrinking and thinning of the Arctic sea ice.[163] While ice-free summers are expected to be rare at 1.5 °C degrees of warming, they are set to occur once every three to ten years at a warming level of 2 °C.[164] Higher atmospheric CO ₂ concentrations have led to changes in ocean chemistry. An increase in dissolved CO ₂ is causing oceans to acidify.[165] In addition, oxygen levels are decreasing as oxygen is less soluble in warmer water.[166] Dead zones in the ocean, regions with very little oxygen, are expanding too.[167]

Tipping points and long-term impacts

Greater degrees of global warming increase the risk of passing through ' tipping points'-thresholds beyond which certain impacts can no longer be avoided even if temperatures are reduced.[168][169] An example is the collapse of West Antarctic and Greenland ice sheets, where a temperature rise of 1.5 to 2 °C may commit the ice sheets to melt, although the time scale of melt is uncertain and depends on future warming.[170][171] Some large-scale changes could occur over a short time period, such as a shutdown of certain ocean currents like the Atlantic meridional overturning circulation (AMOC).[172] Tipping points can also include irreversible damage to ecosystems like the Amazon rainforest and coral reefs.[173]

The long-term effects of climate change on oceans include further ice melt, ocean warming, sea level rise, and ocean acidification.[174] On the timescale of centuries to millennia, the magnitude of climate change will be determined primarily by anthropogenic CO ₂ emissions. This is due to CO ₂'s long atmospheric lifetime.[175] Oceanic CO ₂ uptake is slow enough that ocean acidification will continue for hundreds to thousands of years. These emissions are estimated to have prolonged the current interglacial period by at least 100,000 years.[177] Sea level rise will continue over many centuries, with an estimated rise of 2.3 metres per degree Celsius (4.2 ft/°F) after 2000 years.[178]

Nature and wildlife

Recent warming has driven many terrestrial and freshwater species poleward and towards higher altitudes.[179] Higher atmospheric CO ₂ levels and an extended growing season have resulted in global greening. However, heatwaves and drought have reduced ecosystem productivity in some regions. The future balance of these opposing effects is unclear. Climate change has contributed to the expansion of drier climate zones, such as the expansion of deserts in the subtropics.[181] The size and speed of global warming is making abrupt changes in ecosystems more likely. Overall, it is expected that climate change will result in the extinction of many species.

The oceans have heated more slowly than the land, but plants and animals in the ocean have migrated towards the colder poles faster than species on land.[184] Just as on land, heat waves in the ocean occur more frequently due to climate change, harming a wide range of organisms such as corals, kelp, and seabirds.[185] Ocean acidification makes it harder for marine calcifying organisms such as mussels, barnacles and corals to produce shells and skeletons; and heatwaves have bleached coral reefs. Harmful algal blooms enhanced by climate change and eutrophication lower oxygen levels, disrupt food webs and cause great loss of marine life.[187] Coastal ecosystems are under particular stress. Almost half of global wetlands have disappeared due to climate change and other human impacts.

Humans

The effects of climate change are impacting humans everywhere in the world. Impacts can be observed on all continents and ocean regions,[194] with low-latitude, less developed areas facing the greatest risk.[195] Continued warming has potentially "severe, pervasive and irreversible impacts" for people and ecosystems.[196] The risks are unevenly distributed, but are generally greater for disadvantaged people in developing and developed countries.[197]

Food and health

The WHO calls climate change the greatest threat to global health in the 21st century.[198] Extreme weather leads to injury and loss of life,[199] and crop failures to malnutrition.[200] Various infectious diseases are more easily transmitted in a warmer climate, such as dengue fever and malaria. Young children are the most vulnerable to food shortages. Both children and older people are vulnerable to extreme heat. The World Health Organization (WHO) has estimated that between 2030 and 2050, climate change would cause around 250,000 additional deaths per year. They assessed deaths from heat exposure in elderly people, increases in diarrhea, malaria, dengue, coastal flooding, and childhood malnutrition.[203] Over 500,000 more adult deaths are projected yearly by 2050 due to reductions in food availability and quality.[204] By 2100, 50% to 75% of the global population may face climate conditions that are life-threatening due to combined effects of extreme heat and humidity.[205]

Climate change is affecting food security. It has caused reduction in global yields of maize, wheat, and soybeans between 1981 and 2010.[206] Future warming could further reduce global yields of major crops.[207] Crop production will probably be negatively affected in low-latitude countries, while effects at northern latitudes may be positive or negative.[208] Up to an additional 183 million people worldwide, particularly those with lower incomes, are at risk of hunger as a consequence of these impacts.[209] Climate change also impacts fish populations. Globally, less will be available to be fished. Regions dependent on glacier water, regions that are already dry, and small islands have a higher risk of water stress due to climate change.[211]

Livelihoods

Economic damages due to climate change may be severe and there is a chance of disastrous consequences.[212] Climate change has likely already increased global economic inequality, and this trend is projected to continue.[213] Most of the severe impacts are expected in sub-Saharan Africa, where most of the local inhabitants are dependent upon natural and agricultural resources[214] and South-East Asia.[215] The World Bank estimates that climate change could drive over 120 million people into poverty by 2030.

Inequalities based on wealth and social status have worsened due to climate change.[217] Major difficulties in mitigating, adapting, and recovering to climate shocks are faced by marginalized people who have less control over resources.[218][214] Indigenous people, who are subsistent on their land and ecosystems, will face endangerment to their wellness and lifestyles due to climate change.[219] An expert elicitation concluded that the role of climate change in armed conflict has been small compared to factors such as socio-economic inequality and state capabilities.

Low-lying islands and coastal communities are threatened by sea level rise, which makes flooding more common. Sometimes, land is permanently lost to the sea. This could lead to statelessness for people in island nations, such as the Maldives and Tuvalu.[222] In some regions, the rise in temperature and humidity may be too severe for humans to adapt to. With worst-case climate change, models project that almost one-third of humanity might live in extremely hot and uninhabitable climates, similar to the climate found in the Sahara.[224] These factors can drive environmental migration, both within and between countries.[10] More people are expected to be displaced because of sea level rise, extreme weather and conflict from increased competition over natural resources. Climate change may also increase vulnerability, leading to "trapped populations" who are not able to move due to a lack of resources.[225]

Global greenhouse gas emission scenarios, based on policies and pledges as of 11/21

Climate change can be mitigated by reducing the rate at which greenhouse gases are emitted into the atmosphere, and by increasing the rate at which carbon dioxide is removed from the atmosphere.[231] In order to limit global warming to less than 1.5 °C global greenhouse gas emissions needs to be net-zero by 2050, or by 2070 with a 2 °C target.[148] This requires far-reaching, systemic changes on an unprecedented scale in energy, land, cities, transport, buildings, and industry.[232] The United Nations Environment Programme estimates that countries need to triple their pledges under the Paris Agreement within the next decade to limit global warming to 2 °C. An even greater level of reduction is required to meet the 1.5 °C goal.[233] With pledges made under the Paris Agreement as of October 2021, global warming would still have a 66% chance of reaching about 2.7 °C (range: 2.2-3.2 °C) by the end of the century.[18] Globally, limiting warming to 2 °C may result in higher economic benefits than economic costs.[234]

Although there is no single pathway to limit global warming to 1.5 or 2 °C,[235] most scenarios and strategies see a major increase in the use of renewable energy in combination with increased energy efficiency measures to generate the needed greenhouse gas reductions.[236] To reduce pressures on ecosystems and enhance their carbon sequestration capabilities, changes would also be necessary in agriculture and forestry,[237] such as preventing deforestation and restoring natural ecosystems by reforestation.[238]

Other approaches to mitigating climate change have a higher level of risk. Scenarios that limit global warming to 1.5 °C typically project the large-scale use of carbon dioxide removal methods over the 21st century.[239] There are concerns, though, about over-reliance on these technologies, and environmental impacts.[240] Solar radiation modification (SRM) is also a possible supplement to deep reductions in emissions. However, SRM raises significant ethical and legal concerns, and the risks are imperfectly understood.[241]

Clean energy

Coal, oil, and natural gas remain the primary global energy sources even as renewables have begun rapidly increasing.[242]

Wind and solar power, Germany

Renewable energy is key to limiting climate change.[243] Fossil fuels accounted for 80% of the world's energy in 2018. The remaining share was split between nuclear power and renewables (including hydropower, bioenergy, wind and solar power and geothermal energy).[244] That mix is projected to change significantly over the next 30 years.[236] Solar panels and onshore wind are now among the cheapest forms of adding new power generation capacity in many locations.[245] Renewables represented 75% of all new electricity generation installed in 2019, nearly all solar and wind.[246] Other forms of clean energy, such as nuclear and hydropower, currently have a larger share of the energy supply. However, their future growth forecasts appear limited in comparison.[247]

To achieve carbon neutrality by 2050, renewable energy would become the dominant form of electricity generation, rising to 85% or more by 2050 in some scenarios. Investment in coal would be eliminated and coal use nearly phased out by 2050.[248][249]

Electricity generated from renewable sources would also need to become the main energy source for heating and transport.[250] Transport can switch away from internal combustion engine vehicles and towards electric vehicles, public transit, and active transport (cycling and walking).[251][252] For shipping and flying, low-carbon fuels would reduce emissions.[251] Heating could be increasingly decarbonised with technologies like heat pumps.[253]

There are obstacles to the continued rapid growth of clean energy, including renewables. For wind and solar, there are environmental and land use concerns for new projects.[254] Wind and solar also produce energy intermittently and with seasonal variability. Traditionally, hydro dams with reservoirs and conventional power plants have been used when variable energy production is low. Going forward, battery storage can be expanded, energy demand and supply can be matched, and long-distance transmission can smooth variability of renewable outputs.[243] Bioenergy is often not carbon-neutral and may have negative consequences for food security.[255] The growth of nuclear power is constrained by controversy around radioactive waste, nuclear weapon proliferation, and accidents.[256][257] Hydropower growth is limited by the fact that the best sites have been developed, and new projects are confronting increased social and environmental concerns.[258]

Low-carbon energy improves human health by minimising climate change. It also has the near-term benefit of reducing air pollution deaths,[259] which were estimated at 7 million annually in 2016.[260] Meeting the Paris Agreement goals that limit warming to a 2 °C increase could save about a million of those lives per year by 2050, whereas limiting global warming to 1.5 °C could save millions and simultaneously increase energy security and reduce poverty.[261] Improving air quality also has economic benefits which may be larger than mitigation costs.[262]

Energy conservation

Reducing energy demand is another major aspect of reducing emissions.[263] If less energy is needed, there is more flexibility for clean energy development. It also makes it easier to manage the electricity grid, and minimises carbon-intensive infrastructure development.[264] Major increases in energy efficiency investment will be required to achieve climate goals, comparable to the level of investment in renewable energy.[265] Several COVID-19 related changes in energy use patterns, energy efficiency investments, and funding have made forecasts for this decade more difficult and uncertain.[266]

Strategies to reduce energy demand vary by sector. In the transport sector, passengers and freight can switch to more efficient travel modes, such as buses and trains, or use electric vehicles.[267] Industrial strategies to reduce energy demand include improving heating systems and motors, designing less energy-intensive products, and increasing product lifetimes.[268] In the building sector the focus is on better design of new buildings, and higher levels of energy efficiency in retrofitting.[269] The use of technologies like heat pumps can also increase building energy efficiency.[270]

Agriculture and industry

Taking into account direct and indirect emissions, industry is the sector with the highest share of global emissions. Data as of 2019 from the IPCC.

Agriculture and forestry face a triple challenge of limiting greenhouse gas emissions, preventing the further conversion of forests to agricultural land, and meeting increases in world food demand.[271] A set of actions could reduce agriculture and forestry-based emissions by two thirds from 2010 levels. These include reducing growth in demand for food and other agricultural products, increasing land productivity, protecting and restoring forests, and reducing greenhouse gas emissions from agricultural production.[272]

On the demand side, a key component of reducing emissions is shifting people towards plant-based diets.[273] Eliminating the production of livestock for meat and dairy would eliminate about 3/4ths of all emissions from agriculture and other land use.[274] Livestock also occupy 37% of ice-free land area on Earth and consume feed from the 12% of land area used for crops, driving deforestation and land degradation.[275]

Steel and cement production are responsible for about 13% of industrial CO ₂ emissions. In these industries, carbon-intensive materials such as coke and lime play an integral role in the production, so that reducing CO ₂ emissions requires research into alternative chemistries.[276]

Carbon sequestration

Most CO₂ emissions have been absorbed by carbon sinks, including plant growth, soil uptake, and ocean uptake (2020 Global Carbon Budget).

Natural carbon sinks can be enhanced to sequester significantly larger amounts of CO ₂ beyond naturally occurring levels.[277] Reforestation and tree planting on non-forest lands are among the most mature sequestration techniques, although the latter raises food security concerns.[278] Farmers can promote sequestration of carbon in soils through practices such as use of winter cover crops, reducing the intensity and frequency of tillage, and using compost and manure as soil amendments.[279] In one of its recent publications, FAO maintains that forest and landscape restoration yields many benefits for the climate, including greenhouse gas emissions sequestration and reduction.[105] Restoration/recreation of coastal wetlands, prairie plots and seagrass meadows increases the uptake of carbon into organic matter.[280][281] When carbon is sequestered in soils and in organic matter such as trees, there is a risk of the carbon being re-released into the atmosphere later through changes in land use, fire, or other changes in ecosystems.[282]

Where energy production or CO ₂-intensive heavy industries continue to produce waste CO ₂, the gas can be captured and stored instead of released to the atmosphere. Although its current use is limited in scale and expensive,[283] carbon capture and storage (CCS) may be able to play a significant role in limiting CO ₂ emissions by mid-century. This technique, in combination with bioenergy ( BECCS) can result in net negative emissions: CO ₂ is drawn from the atmosphere.[285] It remains highly uncertain whether carbon dioxide removal techniques will be able to play a large role in limiting warming to 1.5 °C. Policy decisions that rely on carbon dioxide removal increase the risk of global warming rising beyond international goals.[286]

The Climate Change Performance Index ranks countries by greenhouse gas emissions (40% of score), renewable energy (20%), energy use (20%), and climate policy (20%).

Countries that are most vulnerable to climate change have typically been responsible for a small share of global emissions. This raises questions about justice and fairness.[303] Climate change is strongly linked to sustainable development. Limiting global warming makes it easier to achieve Sustainable Development Goals, such as eradicating poverty and reducing inequalities. The connection is recognised in Sustainable Development Goal 13 which is to "take urgent action to combat climate change and its impacts".[304] The goals on food, clean water and ecosystem protection have synergies with climate mitigation.

The geopolitics of climate change is complex. It has often been framed as a free-rider problem, in which all countries benefit from mitigation done by other countries, but individual countries would lose from switching to a low-carbon economy themselves. This framing has been challenged. For instance, the benefits of a coal phase-out to public health and local environments exceed the costs in almost all regions.[306] Furthermore, net importers of fossil fuels win economically from switching to clean energy, causing net exporters to face stranded assets: fossil fuels they cannot sell.[307]

Policy options

A wide range of policies, regulations, and laws are being used to reduce emissions. As of 2019, carbon pricing covers about 20% of global greenhouse gas emissions.[308] Carbon can be priced with carbon taxes and emissions trading systems.[309] Direct global fossil fuel subsidies reached $319 billion in 2017, and $5.2 trillion when indirect costs such as air pollution are priced in.[310] Ending these can cause a 28% reduction in global carbon emissions and a 46% reduction in air pollution deaths.[311] Money saved on fossil subsidies could be used to support the transition to clean energy instead.[312] More direct methods to reduce greenhouse gases include vehicle efficiency standards, renewable fuel standards, and air pollution regulations on heavy industry.[313] Several countries require utilities to increase the share of renewables in power production.[314]

Climate justice

Policy designed through the lens of climate justice tries to address human rights issues and social inequality. For instance, wealthy nations responsible for the largest share of emissions would have to pay poorer countries to adapt.[315] A 2023 study published in One Earth estimated that the top 21 fossil fuel companies would owe cumulative climate reparations of $5.4 trillion over the period 2025-2050.[316] As the use of fossil fuels is reduced, jobs in the sector are lost. To achieve a just transition, these people would need to be retrained for other jobs. Communities with many fossil fuel workers would need additional investments.[317]

International climate agreements

Since 2000, rising CO₂ emissions in China and the rest of world have surpassed the output of the United States and Europe.[318]

Per person, the United States generates CO₂ at a far faster rate than other primary regions.[318]

Nearly all countries in the world are parties to the 1994 United Nations Framework Convention on Climate Change (UNFCCC).[319] The goal of the UNFCCC is to prevent dangerous human interference with the climate system.[320] As stated in the convention, this requires that greenhouse gas concentrations are stabilised in the atmosphere at a level where ecosystems can adapt naturally to climate change, food production is not threatened, and economic development can be sustained.[321] The UNFCCC does not itself restrict emissions but rather provides a framework for protocols that do. Global emissions have risen since the UNFCCC was signed.[322] Its yearly conferences are the stage of global negotiations.[323]

The 1997 Kyoto Protocol extended the UNFCCC and included legally binding commitments for most developed countries to limit their emissions.[324] During the negotiations, the G77 (representing developing countries) pushed for a mandate requiring developed countries to "[take] the lead" in reducing their emissions,[325] since developed countries contributed most to the accumulation of greenhouse gases in the atmosphere. Per-capita emissions were also still relatively low in developing countries and developing countries would need to emit more to meet their development needs.[326]

The 2009 Copenhagen Accord has been widely portrayed as disappointing because of its low goals, and was rejected by poorer nations including the G77.[327] Associated parties aimed to limit the global temperature rise to below 2 °C.[328] The Accord set the goal of sending $100 billion per year to developing countries for mitigation and adaptation by 2020, and proposed the founding of the Green Climate Fund.[329] As of 2020, only 83.3 billion were delivered. Only in 2023 the target is expected to be achieved.[330]

In 2015 all UN countries negotiated the Paris Agreement, which aims to keep global warming well below 2.0 °C and contains an aspirational goal of keeping warming under 1.5 °C. The agreement replaced the Kyoto Protocol. Unlike Kyoto, no binding emission targets were set in the Paris Agreement. Instead, a set of procedures was made binding. Countries have to regularly set ever more ambitious goals and reevaluate these goals every five years.[332] The Paris Agreement restated that developing countries must be financially supported.[333] As of October 2021, 194 states and the European Union have signed the treaty and 191 states and the EU have ratified or acceded to the agreement.[334]

The 1987 Montreal Protocol, an international agreement to stop emitting ozone-depleting gases, may have been more effective at curbing greenhouse gas emissions than the Kyoto Protocol specifically designed to do so.[335] The 2016 Kigali Amendment to the Montreal Protocol aims to reduce the emissions of hydrofluorocarbons, a group of powerful greenhouse gases which served as a replacement for banned ozone-depleting gases. This made the Montreal Protocol a stronger agreement against climate change.[336]

National responses

In 2019, the United Kingdom parliament became the first national government to declare a climate emergency.[337] Other countries and jurisdictions followed suit.[338] That same year, the European Parliament declared a "climate and environmental emergency".[339] The European Commission presented its European Green Deal with the goal of making the EU carbon-neutral by 2050.[340] Major countries in Asia have made similar pledges: South Korea and Japan have committed to become carbon-neutral by 2050, and China by 2060.[341] In 2021, the European Commission released its " Fit for 55" legislation package, which contains guidelines for the car industry; all new cars on the European market must be zero-emission vehicles from 2035.[342] While India has strong incentives for renewables, it also plans a significant expansion of coal in the country.[343] Vietnam is among very few coal-dependent fast developing countries that pledged to phase out unabated coal power by the 2040s or as soon as possible thereafter.[344]

As of 2021, based on information from 48 national climate plans, which represent 40% of the parties to the Paris Agreement, estimated total greenhouse gas emissions will be 0.5% lower compared to 2010 levels, below the 45% or 25% reduction goals to limit global warming to 1.5 °C or 2 °C, respectively.[345]

Denial and misinformation

Data has been cherry picked from short periods to falsely assert that global temperatures are not rising. Blue trendlines show short periods that mask longer-term warming trends (red trendlines). Blue dots show the so-called global warming hiatus.

Public debate about climate change has been strongly affected by climate change denial and misinformation, which originated in the United States and has since spread to other countries, particularly Canada and Australia. The actors behind climate change denial form a well-funded and relatively coordinated coalition of fossil fuel companies, industry groups, conservative think tanks, and contrarian scientists.[347] Like the tobacco industry, the main strategy of these groups has been to manufacture doubt about scientific data and results.[348] Many who deny, dismiss, or hold unwarranted doubt about the scientific consensus on anthropogenic climate change are labelled as "climate change skeptics", which several scientists have noted is a misnomer.[349]

There are different variants of climate denial: some deny that warming takes place at all, some acknowledge warming but attribute it to natural influences, and some minimise the negative impacts of climate change.[350] Manufacturing uncertainty about the science later developed into a manufactured controversy: creating the belief that there is significant uncertainty about climate change within the scientific community in order to delay policy changes.[351] Strategies to promote these ideas include criticism of scientific institutions,[352] and questioning the motives of individual scientists.[350] An echo chamber of climate-denying blogs and media has further fomented misunderstanding of climate change.[353]

Public awareness and opinion

The public substantially underestimates the degree of scientific consensus that humans are causing climate change.[354] Studies from 2019 to 2021[355][3][356] found scientific consensus to range from 98.7 to 100%.

Climate change came to international public attention in the late 1980s.[357] Due to media coverage in the early 1990s, people often confused climate change with other environmental issues like ozone depletion.[358] In popular culture, the climate fiction movie The Day After Tomorrow (2004) and the Al Gore documentary An Inconvenient Truth (2006) focused on climate change.[357]

Significant regional, gender, age and political differences exist in both public concern for, and understanding of, climate change. More highly educated people, and in some countries, women and younger people, were more likely to see climate change as a serious threat.[359] Partisan gaps also exist in many countries,[360] and countries with high CO ₂ emissions tend to be less concerned.[361] Views on causes of climate change vary widely between countries.[362] Concern has increased over time,[360] to the point where in 2021 a majority of citizens in many countries express a high level of worry about climate change, or view it as a global emergency.[363] Higher levels of worry are associated with stronger public support for policies that address climate change.[364]

Climate movement

Climate protests demand that political leaders take action to prevent climate change. They can take the form of public demonstrations, fossil fuel divestment, lawsuits and other activities.[365] Prominent demonstrations include the School Strike for Climate. In this initiative, young people across the globe have been protesting since 2018 by skipping school on Fridays, inspired by Swedish teenager Greta Thunberg.[366] Mass civil disobedience actions by groups like Extinction Rebellion have protested by disrupting roads and public transport.[367] Litigation is increasingly used as a tool to strengthen climate action from public institutions and companies. Activists also initiate lawsuits which target governments and demand that they take ambitious action or enforce existing laws on climate change.[368] Lawsuits against fossil-fuel companies generally seek compensation for loss and damage.[369]

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In common usage, climate change describes global warming-the ongoing increase in global average temperature-and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to Earth's climate.

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Climate Change: Vital Signs of the Planet

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Key Takeaway:

Earth's global average surface temperature in 2020 statistically tied with 2016 as the hottest year on record, continuing a long-term warming trend due to human activities.

This graph shows the change in global surface temperature compared to the long-term average from 1951 to 1980. The year 2020 statistically tied with 2016 for the hottest year on record since recordkeeping began in 1880 (source: NASA/GISS). NASA's analyses generally match independent analyses prepared by National Oceanic and Atmospheric Administration (NOAA) and other institutions.

The animation on the right shows the change in global surface temperatures. Dark blue shows areas cooler than average. Dark red shows areas warmer than average. Short-term variations are smoothed out using a 5-year running average to make trends more visible in this map.

The data shown are the latest available, updated annually.

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Global Surface Temperature | NASA Global Climate Change

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A graph and an animated time series showing the change in global surface temperature relative to 1951-1980 average temperatures. The year 2020 ties with 2016 as the warmest on record.

# data[].attributes.attachment_link.title
Carbon dioxide in Earth’s atmosphere - Wikipedia

# data[].attributes.attachment_link.description
Carbon dioxide (CO2) is an important trace gas in Earth’s atmosphere. It is an integral part of the carbon cycle, a biogeochemical cycle in which carbon is exchanged between the Earth’s oceans, soil, rocks and the biosphere. Plants and other photoautotrophs use solar energy to produce carbohydrate f…

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이서준 윤정후

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https://www.arcticwwf.org/wildlife/polar-bear/polar-bear-population/

# data[].attributes.attachment_link.readable_text
Before 1973

Polar bears are an integral part of the Arctic ecosystem and the food web for Indigenous Peoples - who have hunted polar bears sustainably for millennia. But, beginning in the 1700s, large-scale hunting by European, Russian and North American hunters and trappers took place, raising concerns about the future survival of polar bears. Unregulated commercial and recreational hunting continued until the 1970s.

1973

Canada, the United States, Denmark, Norway and the former USSR signed the International Agreement on the Conservation of Polar Bears and their Habitat, strictly regulating commercial hunting.

The US Government classified the Polar Bear under its Endangered Species Act (ESA).
2005
The polar bear was upgraded from Least Concern to Vulnerable by the the IUCN Polar Bear Specialist Group.
2013
Ministers and other leaders from the five polar bear range states met in Moscow for the first International Forum on Polar Bear Conservation. The leaders made significant commitments to address issues of polar bear habitat, research and trade. This event was supported by WWF.

Today

Today, polar bears are among the few large carnivores that are still found in roughly their original habitat and range-and in some places, in roughly their natural numbers.

Although most of the world's 19 populations have returned to healthy numbers, there are differences between them. Some are stable, some seem to be increasing, and some are decreasing due to various pressures.

Status of the polar bear populations
Updated 2021 with data from the IUCN Polar Bear Specialists Group:

3 populations are in decline
2 populations are increasing
4 populations are stable
10 populations are data-deficient (information missing or outdated)

In the future

By 2040, scientists predict that only a fringe of ice will remain in Northeast Canada and Northern Greenland when all other large areas of summer ice are gone. This "Last Ice Area" is likely to become important for polar bears and other life that depends on ice.

A projection of sea ice in the archipelago, supported by WWF, shows that much of the region is facing significant ice loss in the coming decades - with potentially serious consequences for polar bears.
Global polar bear numbers are projected to decline by 30% by 2050.

# data[].attributes.attachment_link.description
How many polar bears are there? See current polar bear populations, IUCN Red List status by country and timeline of polar bear conservation.

# data[].attributes.body
https://climate-nasa-gov.cdn.ampproject.org/v/s/climate.nasa.gov/global-warming-vs-climate-change.amp?amp_gsa=1&amp_js_v=a9&usqp=mq331AQKKAFQArABIIACAw%3D%3D#amp_tf=%EC%B6%9C%EC%B2%98%3A%20%251%24s&aoh=16643271211538&referrer=https%3A%2F%2Fwww.google.com&ampshare=https%3A%2F%2Fclimate.nasa.gov%2Fglobal-warming-vs-climate-change

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Climate Change: Vital Signs of the Planet

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"Climate change" and "global warming" are often used interchangeably but have distinct meanings. Similarly, the terms "weather" and "climate" are sometimes confused, though they refer to events with broadly different spatial- and timescales.

Weather vs. Climate

"If you don't like the weather in New England, just wait a few minutes."

Weather refers to atmospheric conditions that occur locally over short periods of time-from minutes to hours or days. Familiar examples include rain, snow, clouds, winds, floods, or thunderstorms.

Climate, on the other hand, refers to the long-term (usually at least 30 years) regional or even global average of temperature, humidity, and rainfall patterns over seasons, years, or decades.

What is Global Warming?

Global warming is the long-term heating of Earth's surface observed since the pre-industrial period (between 1850 and 1900) due to human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth's atmosphere. This term is not interchangeable with the term "climate change."

Since the pre-industrial period, human activities are estimated to have increased Earth's global average temperature by about 1 degree Celsius (1.8 degrees Fahrenheit), a number that is currently increasing by more than 0.2 degrees Celsius (0.36 degrees Fahrenheit) per decade. The current warming trend is unequivocally the result of human activity since the 1950s and is proceeding at an unprecedented rate over millennia.

What is Climate Change?

Climate change is a long-term change in the average weather patterns that have come to define Earth's local, regional and global climates. These changes have a broad range of observed effects that are synonymous with the term.

Changes observed in Earth's climate since the mid-20th century are driven by human activities, particularly fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth's atmosphere, raising Earth's average surface temperature. Natural processes, which have been overwhelmed by human activities, can also contribute to climate change, including internal variability (e.g., cyclical ocean patterns like El Niño, La Niña and the Pacific Decadal Oscillation) and external forcings (e.g., volcanic activity, changes in the Sun's energy output, variations in Earth's orbit).

Scientists use observations from the ground, air, and space, along with computer models, to monitor and study past, present, and future climate change. Climate data records provide evidence of climate change key indicators, such as global land and ocean temperature increases; rising sea levels; ice loss at Earth's poles and in mountain glaciers; frequency and severity changes in extreme weather such as hurricanes, heatwaves, wildfires, droughts, floods, and precipitation; and cloud and vegetation cover changes.

Find Out More: A Guide to NASA's Global Climate Change Website

This website provides a high-level overview of some of the known causes, effects and indications of global climate change:

Evidence. Brief descriptions of some of the key scientific observations that our planet is undergoing abrupt climate change.

Causes. A concise discussion of the primary climate change causes on our planet.

Effects. A look at some of the likely future effects of climate change, including U.S. regional effects.

Vital Signs. Graphs and animated time series showing real-time climate change data, including atmospheric carbon dioxide, global temperature, sea ice extent, and ice sheet volume.

Earth Minute. This fun video series explains various Earth science topics, including some climate change topics.

Other NASA Resources

Goddard Scientific Visualization Studio. An extensive collection of animated climate change and Earth science visualizations.

Sea Level Change Portal. NASA's portal for an in-depth look at the science behind sea level change.

NASA's Earth Observatory. Satellite imagery, feature articles and scientific information about our home planet, with a focus on Earth's climate and environmental change.
Shutterstock credits: wandee007 (left), Amy Johansson (middle), Avatar_023 (right).

# data[].attributes.attachment_link.title
Overview: Weather, Global Warming and Climate Change

# data[].attributes.attachment_link.description
"Climate change" and "global warming" are often used interchangeably but have distinct meanings. Similarly, the terms "weather" and "climate" are sometimes confused, though they refer to events with broadly different spatial- and timescales. "If you don't like the weather in New England, just wait a few minutes."

# data[].attributes.body
이지우 손예찬 일승빈
https://en.m.wikipedia.org/wiki/Climate_change

# data[].attributes.body
https://www.nhm.ac.uk/discover/quick-questions/how-does-carbon-dioxide-increase-global-temperature.html

# data[].attributes.headline
지구 온난화는 거짓일까? - 슬로우뉴스 - https://slownews.kr/37555

# data[].attributes.subject
지구 온난화는 거짓일까? - 슬로우뉴스 - https://slownews.kr/37555

# data[].attributes.body
20422함동현 20407박준현

# data[].attributes.attachment_link.readable_text
Before 1973

Polar bears are an integral part of the Arctic ecosystem and the food web for Indigenous Peoples - who have hunted polar bears sustainably for millennia. But, beginning in the 1700s, large-scale hunting by European, Russian and North American hunters and trappers took place, raising concerns about the future survival of polar bears. Unregulated commercial and recreational hunting continued until the 1970s.

1973

Canada, the United States, Denmark, Norway and the former USSR signed the International Agreement on the Conservation of Polar Bears and their Habitat, strictly regulating commercial hunting.

The US Government classified the Polar Bear under its Endangered Species Act (ESA).
2005
The polar bear was upgraded from Least Concern to Vulnerable by the the IUCN Polar Bear Specialist Group.
2013
Ministers and other leaders from the five polar bear range states met in Moscow for the first International Forum on Polar Bear Conservation. The leaders made significant commitments to address issues of polar bear habitat, research and trade. This event was supported by WWF.

Today

Today, polar bears are among the few large carnivores that are still found in roughly their original habitat and range-and in some places, in roughly their natural numbers.

Although most of the world's 19 populations have returned to healthy numbers, there are differences between them. Some are stable, some seem to be increasing, and some are decreasing due to various pressures.

Status of the polar bear populations
Updated 2021 with data from the IUCN Polar Bear Specialists Group:

3 populations are in decline
2 populations are increasing
4 populations are stable
10 populations are data-deficient (information missing or outdated)

In the future

By 2040, scientists predict that only a fringe of ice will remain in Northeast Canada and Northern Greenland when all other large areas of summer ice are gone. This "Last Ice Area" is likely to become important for polar bears and other life that depends on ice.

A projection of sea ice in the archipelago, supported by WWF, shows that much of the region is facing significant ice loss in the coming decades - with potentially serious consequences for polar bears.
Global polar bear numbers are projected to decline by 30% by 2050.

# data[].attributes.attachment_link.description
How many polar bears are there? See current polar bear populations, IUCN Red List status by country and timeline of polar bear conservation.

# data[].attributes.body
https://www.arcticwwf.org/wildlife/polar-bear/polar-bear-population/

# data[].attributes.attachment_link.readable_text
Before 1973

Polar bears are an integral part of the Arctic ecosystem and the food web for Indigenous Peoples - who have hunted polar bears sustainably for millennia. But, beginning in the 1700s, large-scale hunting by European, Russian and North American hunters and trappers took place, raising concerns about the future survival of polar bears. Unregulated commercial and recreational hunting continued until the 1970s.

1973

Canada, the United States, Denmark, Norway and the former USSR signed the International Agreement on the Conservation of Polar Bears and their Habitat, strictly regulating commercial hunting.

The US Government classified the Polar Bear under its Endangered Species Act (ESA).
2005
The polar bear was upgraded from Least Concern to Vulnerable by the the IUCN Polar Bear Specialist Group.
2013
Ministers and other leaders from the five polar bear range states met in Moscow for the first International Forum on Polar Bear Conservation. The leaders made significant commitments to address issues of polar bear habitat, research and trade. This event was supported by WWF.

Today

Today, polar bears are among the few large carnivores that are still found in roughly their original habitat and range-and in some places, in roughly their natural numbers.

Although most of the world's 19 populations have returned to healthy numbers, there are differences between them. Some are stable, some seem to be increasing, and some are decreasing due to various pressures.

Status of the polar bear populations
Updated 2021 with data from the IUCN Polar Bear Specialists Group:

3 populations are in decline
2 populations are increasing
4 populations are stable
10 populations are data-deficient (information missing or outdated)

In the future

By 2040, scientists predict that only a fringe of ice will remain in Northeast Canada and Northern Greenland when all other large areas of summer ice are gone. This "Last Ice Area" is likely to become important for polar bears and other life that depends on ice.

A projection of sea ice in the archipelago, supported by WWF, shows that much of the region is facing significant ice loss in the coming decades - with potentially serious consequences for polar bears.
Global polar bear numbers are projected to decline by 30% by 2050.

# data[].attributes.attachment_link.description
How many polar bears are there? See current polar bear populations, IUCN Red List status by country and timeline of polar bear conservation.

# data[].attributes.body
https://education.nationalgeographic.org/resource/sea-level-rise

# data[].attributes.attachment_link.readable_text
Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Director

Author

National Geographic Society

Production Managers

Program Specialists

other

# data[].attributes.attachment_link.title
Sea Level Rise | National Geographic Society

# data[].attributes.attachment_link.description
Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited. Director Author National Geographic Society Production Managers Program Specialists other

# data[].attributes.body
https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide

# data[].attributes.attachment_link.readable_text
Based on the annual report from NOAA's Global Monitoring Lab, global average atmospheric carbon dioxide was 417.06 parts per million ("ppm" for short) in 2022, setting a new record high. The increase between 2021 and 2022 was 2.13 ppm-the 11 th year in a row where the amount of carbon dioxide in the atmosphere increased by more than 2 ppm. At Mauna Loa Observatory in Hawaii, where the modern carbon dioxide record began in 1958, the annual average carbon dioxide in 2022 was 418.56.

Carbon dioxide concentrations are rising mostly because of the fossil fuels that people are burning for energy. Fossil fuels like coal and oil contain carbon that plants pulled out of the atmosphere through photosynthesis over many millions of years; we are returning that carbon to the atmosphere in just a few hundred. Since the middle of the 20 th century, annual emissions from burning fossil fuels have increased every decade, from close to 11 billion tons of carbon dioxide per year in the 1960s to an estimated 36.6 billion tons in 2022 according to the Global Carbon Budget 2022.

Carbon cycle experts estimate that natural "sinks"-processes that remove carbon from the atmosphere-on land and in the ocean absorbed the equivalent of about half of the carbon dioxide we emitted each year in the 2011-2020 decade. Because we put more carbon dioxide into the atmosphere than natural sinks can remove, the total amount of carbon dioxide in the atmosphere increases every year.

The more we overshoot what natural processes can remove in a given year, the faster the atmospheric concentration of carbon dioxide rises. In the 1960s, the global growth rate of atmospheric carbon dioxide was roughly 0.8± 0.1 ppm per year. Over the next half century, the annual growth rate tripled, reaching 2.4 ppm per year during the 2010s. The annual rate of increase in atmospheric carbon dioxide over the past 60 years is about 100 times faster than previous natural increases, such as those that occurred at the end of the last ice age 11,000-17,000 years ago.

Why carbon dioxide matters

Carbon dioxide is Earth's most important greenhouse gas: a gas that absorbs and radiates heat. Unlike oxygen or nitrogen (which make up most of our atmosphere), greenhouse gases absorb heat radiating from the Earth's surface and re-release it in all directions-including back toward Earth's surface. Without carbon dioxide, Earth's natural greenhouse effect would be too weak to keep the average global surface temperature above freezing. By adding more carbon dioxide to the atmosphere, people are supercharging the natural greenhouse effect, causing global temperature to rise. According to observations by the NOAA Global Monitoring Lab, in 2021 carbon dioxide alone was responsible for about two-thirds of the total heating influence of all human-produced greenhouse gases.

Another reason carbon dioxide is important in the Earth system is that it dissolves into the ocean like the fizz in a can of soda. It reacts with water molecules, producing carbonic acid and lowering the ocean's pH (raising its acidity). Since the start of the Industrial Revolution, the pH of the ocean's surface waters has dropped from 8.21 to 8.10. This drop in pH is called ocean acidification.

Past and future carbon dioxide

Natural increases in carbon dioxide concentrations have periodically warmed Earth's temperature during ice age cycles over the past million years or more. The warm episodes (interglacials) began with a small increase in incoming sunlight in the Northern Hemisphere due to variations in Earth's orbit around the Sun and its axis of rotation. (For more details, see the "Milankovitch cycles and ice ages" section of our Climate change: incoming sunlight article.) That little bit of extra sunlight caused a little bit of warming. As the oceans warmed, they outgassed carbon dioxide-like a can of soda going flat in the heat of a summer day. The extra carbon dioxide in the atmosphere greatly amplified the initial, solar-driven warming.

Based on air bubbles trapped in mile-thick ice cores and other paleoclimate evidence, we know that during the ice age cycles of the past million years or so, atmospheric carbon dioxide never exceeded 300 ppm. Before the Industrial Revolution started in the mid-1700s, atmospheric carbon dioxide was 280 ppm or less.

By the time continuous observations began at Mauna Loa Volcanic Observatory in 1958, global atmospheric carbon dioxide was already 315 ppm. Carbon dioxide levels today are higher than at any point in human history. In fact, the last time atmospheric carbon dioxide amounts were this high was more than 3 million years ago, during the Mid-Pliocene Warm Period, when global surface temperature was 4.5-7.2 degrees Fahrenheit (2.5-4 degrees Celsius) warmer than during the pre-industrial era. Sea level was at least 16 feet higher than it was in 1900 and possibly as much as 82 feet higher.

If global energy demand continues to grow rapidly and we meet it mostly with fossil fuels, human emissions of carbon dioxide could reach 75 billion tons per year or more by the end of the century. Atmospheric carbon dioxide could be 800 ppm or higher-conditions not seen on Earth for close to 50 million years.

More on carbon dioxide
NOAA carbon dioxide observations Carbon cycle factsheet Carbon dioxide emissions by country over time Comparing greenhouse gases by their global warming potential Ocean acidification
References

Collins, M., R. Knutti, J. Arblaster, J.-L. Dufresne, T. Fichefet, P. Friedlingstein, X. Gao, W.J. Gutowski, T. Johns, G. Krinner, M. Shongwe, C. Tebaldi, A.J. Weaver and M. Wehner, 2013: Long-term Climate Change: Projections, Commitments and Irreversibility. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Friedlingstein, P., O'Sullivan, M., Jones, M. W., Andrew, R. M., Gregor, L., Hauck, J., Le Quéré, C., Luijkx, I. T., Olsen, A., Peters, G. P., Peters, W., Pongratz, J., Schwingshackl, C., Sitch, S., Canadell, J. G., Ciais, P., Jackson, R. B., Alin, S. R., Alkama, R., ... Zheng, B. (2022). Global Carbon Budget 2022. Earth System Science Data, 14(11), 4811-4900. https://doi.org/10.5194/essd-14-4811-2022

Lan, X., B. D. Hall, G. Dutton, J. Mühle, J. W. Elkins, and I. J. Vimont. (2022). Long-lived greenhouses gases [in State of the Climate in 2021, Chapter 2: Global Climate]. Bulletin of the American Meteorological Society, 103 (8), S81-S84. https://doi.org/10.1175/BAMS-D-22-0092.1.

Lüthi, D., M. Le Floch, B. Bereiter, T. Blunier, J.-M. Barnola, U. Siegenthaler, D. Raynaud, J. Jouzel, H. Fischer, K. Kawamura, and T.F. Stocker. (2008). High-resolution carbon dioxide concentration record 650,000-800,000 years before present. Nature, Vol. 453, pp. 379-382. doi:10.1038/nature06949.

Woods Hole Oceanographic Institution. (2015). Introduction to ocean acidification. Accessed October 4, 2017.

Lindsey, R. (2009). Climate and Earth's energy budget. Accessed October 4, 2017.

Based on the annual report from NOAA's Global Monitoring Lab, global average atmospheric carbon dioxide was 417.06 parts per million ("ppm" for short) in 2022, setting a new record high. The increase between 2021 and 2022 was 2.13 ppm-the 11 th year in a row where the amount of carbon dioxide in the atmosphere increased by more than 2 ppm. At Mauna Loa Observatory in Hawaii, where the modern carbon dioxide record began in 1958, the annual average carbon dioxide in 2022 was 418.56.

Carbon dioxide concentrations are rising mostly because of the fossil fuels that people are burning for energy. Fossil fuels like coal and oil contain carbon that plants pulled out of the atmosphere through photosynthesis over many millions of years; we are returning that carbon to the atmosphere in just a few hundred. Since the middle of the 20 th century, annual emissions from burning fossil fuels have increased every decade, from close to 11 billion tons of carbon dioxide per year in the 1960s to an estimated 36.6 billion tons in 2022 according to the Global Carbon Budget 2022.

Carbon cycle experts estimate that natural "sinks"-processes that remove carbon from the atmosphere-on land and in the ocean absorbed the equivalent of about half of the carbon dioxide we emitted each year in the 2011-2020 decade. Because we put more carbon dioxide into the atmosphere than natural sinks can remove, the total amount of carbon dioxide in the atmosphere increases every year.

The more we overshoot what natural processes can remove in a given year, the faster the atmospheric concentration of carbon dioxide rises. In the 1960s, the global growth rate of atmospheric carbon dioxide was roughly 0.8± 0.1 ppm per year. Over the next half century, the annual growth rate tripled, reaching 2.4 ppm per year during the 2010s. The annual rate of increase in atmospheric carbon dioxide over the past 60 years is about 100 times faster than previous natural increases, such as those that occurred at the end of the last ice age 11,000-17,000 years ago.

Why carbon dioxide matters

Carbon dioxide is Earth's most important greenhouse gas: a gas that absorbs and radiates heat. Unlike oxygen or nitrogen (which make up most of our atmosphere), greenhouse gases absorb heat radiating from the Earth's surface and re-release it in all directions-including back toward Earth's surface. Without carbon dioxide, Earth's natural greenhouse effect would be too weak to keep the average global surface temperature above freezing. By adding more carbon dioxide to the atmosphere, people are supercharging the natural greenhouse effect, causing global temperature to rise. According to observations by the NOAA Global Monitoring Lab, in 2021 carbon dioxide alone was responsible for about two-thirds of the total heating influence of all human-produced greenhouse gases.

Another reason carbon dioxide is important in the Earth system is that it dissolves into the ocean like the fizz in a can of soda. It reacts with water molecules, producing carbonic acid and lowering the ocean's pH (raising its acidity). Since the start of the Industrial Revolution, the pH of the ocean's surface waters has dropped from 8.21 to 8.10. This drop in pH is called ocean acidification.

Past and future carbon dioxide

Natural increases in carbon dioxide concentrations have periodically warmed Earth's temperature during ice age cycles over the past million years or more. The warm episodes (interglacials) began with a small increase in incoming sunlight in the Northern Hemisphere due to variations in Earth's orbit around the Sun and its axis of rotation. (For more details, see the "Milankovitch cycles and ice ages" section of our Climate change: incoming sunlight article.) That little bit of extra sunlight caused a little bit of warming. As the oceans warmed, they outgassed carbon dioxide-like a can of soda going flat in the heat of a summer day. The extra carbon dioxide in the atmosphere greatly amplified the initial, solar-driven warming.

Based on air bubbles trapped in mile-thick ice cores and other paleoclimate evidence, we know that during the ice age cycles of the past million years or so, atmospheric carbon dioxide never exceeded 300 ppm. Before the Industrial Revolution started in the mid-1700s, atmospheric carbon dioxide was 280 ppm or less.

By the time continuous observations began at Mauna Loa Volcanic Observatory in 1958, global atmospheric carbon dioxide was already 315 ppm. Carbon dioxide levels today are higher than at any point in human history. In fact, the last time atmospheric carbon dioxide amounts were this high was more than 3 million years ago, during the Mid-Pliocene Warm Period, when global surface temperature was 4.5-7.2 degrees Fahrenheit (2.5-4 degrees Celsius) warmer than during the pre-industrial era. Sea level was at least 16 feet higher than it was in 1900 and possibly as much as 82 feet higher.

If global energy demand continues to grow rapidly and we meet it mostly with fossil fuels, human emissions of carbon dioxide could reach 75 billion tons per year or more by the end of the century. Atmospheric carbon dioxide could be 800 ppm or higher-conditions not seen on Earth for close to 50 million years.

More on carbon dioxide
NOAA carbon dioxide observations Carbon cycle factsheet Carbon dioxide emissions by country over time Comparing greenhouse gases by their global warming potential Ocean acidification
References

Collins, M., R. Knutti, J. Arblaster, J.-L. Dufresne, T. Fichefet, P. Friedlingstein, X. Gao, W.J. Gutowski, T. Johns, G. Krinner, M. Shongwe, C. Tebaldi, A.J. Weaver and M. Wehner, 2013: Long-term Climate Change: Projections, Commitments and Irreversibility. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Friedlingstein, P., O'Sullivan, M., Jones, M. W., Andrew, R. M., Gregor, L., Hauck, J., Le Quéré, C., Luijkx, I. T., Olsen, A., Peters, G. P., Peters, W., Pongratz, J., Schwingshackl, C., Sitch, S., Canadell, J. G., Ciais, P., Jackson, R. B., Alin, S. R., Alkama, R., ... Zheng, B. (2022). Global Carbon Budget 2022. Earth System Science Data, 14(11), 4811-4900. https://doi.org/10.5194/essd-14-4811-2022

Lan, X., B. D. Hall, G. Dutton, J. Mühle, J. W. Elkins, and I. J. Vimont. (2022). Long-lived greenhouses gases [in State of the Climate in 2021, Chapter 2: Global Climate]. Bulletin of the American Meteorological Society, 103 (8), S81-S84. https://doi.org/10.1175/BAMS-D-22-0092.1.

Lüthi, D., M. Le Floch, B. Bereiter, T. Blunier, J.-M. Barnola, U. Siegenthaler, D. Raynaud, J. Jouzel, H. Fischer, K. Kawamura, and T.F. Stocker. (2008). High-resolution carbon dioxide concentration record 650,000-800,000 years before present. Nature, Vol. 453, pp. 379-382. doi:10.1038/nature06949.

Woods Hole Oceanographic Institution. (2015). Introduction to ocean acidification. Accessed October 4, 2017.

Lindsey, R. (2009). Climate and Earth's energy budget. Accessed October 4, 2017.

# data[].attributes.attachment_link.title
Climate Change: Atmospheric Carbon Dioxide

# data[].attributes.attachment_link.description
In the past 60 years, carbon dioxide in the atmosphere has increased 100 times faster than it did during the end of the last ice age.

# data[].attributes.body
https://m.post.naver.com/viewer/postView.nhn?volumeNo=5724702&memberNo=29949587&vType=VERTICAL

# data[].attributes.attachment_link.description
[BY 인사이트] [인사이트] 심민현 기자 = 미국 어류·야생동식물 보호국은 ”북극곰 개체수가 2050년에 이...

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Before 1973

Polar bears are an integral part of the Arctic ecosystem and the food web for Indigenous Peoples - who have hunted polar bears sustainably for millennia. But, beginning in the 1700s, large-scale hunting by European, Russian and North American hunters and trappers took place, raising concerns about the future survival of polar bears. Unregulated commercial and recreational hunting continued until the 1970s.

1973

Canada, the United States, Denmark, Norway and the former USSR signed the International Agreement on the Conservation of Polar Bears and their Habitat, strictly regulating commercial hunting.

The US Government classified the Polar Bear under its Endangered Species Act (ESA).
2005
The polar bear was upgraded from Least Concern to Vulnerable by the the IUCN Polar Bear Specialist Group.
2013
Ministers and other leaders from the five polar bear range states met in Moscow for the first International Forum on Polar Bear Conservation. The leaders made significant commitments to address issues of polar bear habitat, research and trade. This event was supported by WWF.

Today

Today, polar bears are among the few large carnivores that are still found in roughly their original habitat and range-and in some places, in roughly their natural numbers.

Although most of the world's 19 populations have returned to healthy numbers, there are differences between them. Some are stable, some seem to be increasing, and some are decreasing due to various pressures.

Status of the polar bear populations
Updated 2021 with data from the IUCN Polar Bear Specialists Group:

3 populations are in decline
2 populations are increasing
4 populations are stable
10 populations are data-deficient (information missing or outdated)

In the future

By 2040, scientists predict that only a fringe of ice will remain in Northeast Canada and Northern Greenland when all other large areas of summer ice are gone. This "Last Ice Area" is likely to become important for polar bears and other life that depends on ice.

A projection of sea ice in the archipelago, supported by WWF, shows that much of the region is facing significant ice loss in the coming decades - with potentially serious consequences for polar bears.
Global polar bear numbers are projected to decline by 30% by 2050.

# data[].attributes.attachment_link.description
How many polar bears are there? See current polar bear populations, IUCN Red List status by country and timeline of polar bear conservation.

# data[].attributes.body
https://www.arcticwwf.org/wildlife/polar-bear/polar-bear-population/

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https://blog.naver.com/turbolag14/222162637792

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카오스 스토리 : 네이버 블로그

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https://m.search.naver.com/p/crd/rd?m=1&px=86&py=2355&sx=86&sy=309&p=hzMlSdqVbxVssCV0j60ssssss3N-435422&q=%EC%A7%80%EA%B5%AC+%EC%98%A8%EB%82%9C%ED%99%94%EC%99%80+%EC%A7%80%EA%B5%AC+%ED%95%B4%EC%88%98%EB%A9%B4+%EC%83%81%EC%8A%B9&ie=utf8&rev=1&ssc=tab.m.all&f=m&w=m&s=KqeU1va0OMUfRew%2Fvlmwiw%3D%3D&time=1664327790551&abt=%5B%7B%22eid%22%3A%222%22%2C%22vid%22%3A%223%22%7D%5D&a=web_gen*w.link&r=2&i=a00000fa_28ecad37764a731876f2025e&u=https%3A%2F%2Fwww.koem.or.kr%2Fsimulation%2Fgmsl%2Frcp45.do&cr=3

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https://climate.nasa.gov/vital-signs/carbon-dioxide/

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Climate Change: Vital Signs of the Planet

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Carbon dioxide (CO ₂) is an important heat-trapping gas, also known as a greenhouse gas, that comes from the extraction and burning of fossil fuels (such as coal, oil, and natural gas), from wildfires, and natural processes like volcanic eruptions. The first graph shows atmospheric CO ₂ levels measured by NOAA at Mauna Loa Observatory, Hawaii, since 1958. The second graph shows CO ₂ levels during Earth's last three glacial cycles, as captured by air bubbles trapped in ice sheets and glaciers.

Since the onset of industrial times in the 18th century, human activities have raised atmospheric CO ₂ by 50% - meaning the amount of CO ₂ is now 150% of its value in 1750. This human-induced rise is greater than the natural increase observed at the end of the last ice age 20,000 years ago.

The animated map shows how the historical changes in global carbon dioxide over time. Note the colors change as the amount of CO ₂ rises from 365 parts per million (ppm) in 2002 to over 420 ppm currently. It's important to understand that "parts per million" refers to the number of carbon dioxide molecules per million molecules of dry air. These measurements are from the mid-troposphere, the layer of Earth's atmosphere that is 8 to 12 kilometers (about 5 to 7 miles) above the ground. This data provides insights into the significant rise in atmospheric CO2 concentrations, highlighting the impact of human activities on Earth's climate.

CO₂ Through the Seasons

A closer look at the carbon dioxide measurements at Mauna Loa shows a series of wiggles in the data. Although total CO ₂ is increasing each year, there is also a short-term cycle visible within the larger trend.

This annual rise and fall of CO ₂ levels is caused by seasonal cycles in photosynthesis on a massive scale. In Northern Hemisphere spring, plants come to life and draw in CO ₂ to fuel their growth. This begins the process of lowering the amount of CO ₂ in the atmosphere. In northern autumn, plant growth stops or slows down, and the whole process reverses itself. Much of the plant matter decomposes, releasing CO ₂ back to the atmosphere.

A similar but less intense pattern repeats in the Southern Hemisphere in opposite seasons. Spring growth starts in September and winter decomposition begins in March, so CO ₂ records in the Southern Hemisphere show the opposite pattern of that seen in Mauna Loa. However, because there is a lot more land and vegetation in the Northern Hemisphere than the southern, the global seasonal cycle more closely aligns with the northern pattern.

See the cycle in action in the visualization Watching Earth Breathe: The Seasonal Vegetation Cycle and Atmospheric Carbon Dioxide.

This boom-and-bust cycle of plant growth gives the graph of CO ₂ a sawtooth pattern of ups and downs from year to year. At a larger scale, the upward climb of the trend line over the decades is caused by CO ₂ emissions, primarily from burning fossil fuels. Thus, the data illustrate both natural factors and human additions of CO ₂.

Learn more:

NASA's Climate Kids: Why is Carbon Important?

Missions That Observe CO₂
Atmospheric Infrared Sounder (AIRS) Orbiting Carbon Observatory (OCO-2) Orbiting Carbon Observatory (OCO-3)

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Carbon Dioxide Concentration | NASA Global Climate Change

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Vital Signs of the Planet: Global Climate Change and Global Warming. Current news and data streams about global warming and climate change from NASA.

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Carbon dioxide in Earth's atmosphere - Wikipedia

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Carbon dioxide (CO 2) is an important trace gas in Earth's atmosphere. It is an integral part of the carbon cycle, a biogeochemical cycle in which carbon is exchanged between the Earth's oceans, soil, rocks and the biosphere. Plants and other photoautotrophs use solar energy to produce carbohydrate from atmospheric carbon dioxide and water by photosynthesis.

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https://en.m.wikipedia.org/wiki/Sea_level_rise

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Tide gauge measurements show that the current global sea level rise began at the start of the 20th century. Between 1901 and 2018, the globally averaged sea level rose by 15-25 cm (6-10 in).[1] More precise data gathered from satellite radar measurements reveal an accelerating rise of 7.5 cm (3 in) from 1993 to 2017,[2]: 1554  for an average rate of 3.1 cm ( in) per decade. This acceleration is due mostly to climate change, which heats (and therefore expands) the ocean and which melts the land-based ice sheets and glaciers.[3] Between 1993 and 2018, the thermal expansion of water contributed 42% to sea level rise; melting of temperate glaciers, 21%; Greenland, 15%; and Antarctica, 8%.[2]: 1576  Climate scientists expect the rate to further accelerate during the 21st century, with the latest measurements saying the sea levels are rising by 3.7 mm per year.[4]

Due to the complexity of the climate system and long time lags in sea level reactions to Earth temperature changes, projecting future sea level is challenging. It is almost certain that sea levels will continue to rise. Depending on how strongly greenhouse gas emissions are reduced, further sea level rise from fairly well-understood processes will be around 0.38-0.77 m (1 ft 3 in - 2 ft 6 in) by 2100.[5]: SPM-28  Taking less-understood processes into account, and under a very-high emission scenario, a rise of around two metres ( ft) cannot be excluded.[6][5]: TS-45  Over a longer timescale, the sea level is predicted to rise by 2-3 m (7-10 ft) if global warming is limited to 1.5°C, by up to 6 m ( ft) if it peaks at 2°C and by 19-22 metres (62-72 ft) if it peaks at 5 °C.[5]: SPM-28

The sea level will not rise uniformly everywhere on Earth. Local factors include tectonic effects and subsidence of the land, tides, currents and storms. Sea level rises can affect human populations considerably in coastal and island regions.[7] Widespread coastal flooding is expected with several degrees of warming sustained for millennia.[8] Further effects are higher storm-surges and more dangerous tsunamis, displacement of populations, loss and degradation of agricultural land and damage in cities.[9][10][11] Natural environments like marine ecosystems are also affected, with fish, birds and plants losing parts of their habitat.[12]

Societies can adapt to sea level rise in three different ways: implement managed retreat, accommodate coastal change, or protect against sea level rise through hard-construction practices like seawalls or soft approaches such as dune rehabilitation and beach nourishment. Sometimes these adaptation strategies go hand in hand, but at other times choices have to be made among different strategies.[13] For some human environments, such as so called sinking cities, adaptation to sea level rise may be compounded by other environmental issues such as subsidence. Natural ecosystems typically adapt to rising sea levels by moving inland; however, they might not always be able to do so, due to natural or artificial barriers.[14]

Between 1901 and 2018, the globally averaged sea level rose by 15-25 cm (6-10 in).[1] More precise data gathered from satellite radar measurements reveal an accelerating rise of 7.5 cm (3 in) from 1993 to 2017,[2]: 1554  accelerating gradually to a rate of 3.7 mm (1⁄8 in) per year as of 2021.[4]

Sea level rise is not uniform around the globe. Some land masses are moving up or down as a consequence of subsidence (land sinking or settling) or post-glacial rebound (land rising due to the loss of the weight of ice after melting), so that local relative sea level rise may be higher or lower than the global average. There are even regions near current and former glaciers and ice sheets where sea level falls. Furthermore, gravitational effects of changing ice masses and spatially varying patterns of warming lead to differences in the distribution of sea water around the globe.[15][16] The gravitational effects comes into play when a large ice sheet melts. With the loss of mass, the gravitational pull becomes less and local water levels might drop. Further away from the ice sheet water levels will increase more than average. In this light, melt in Greenland has a different fingerprint on regional sea level than melt in Antarctica.[17]

Many ports, urban conglomerations, and agricultural regions are built on river deltas, where subsidence of land contributes to a substantially increased relative sea level rise. This is caused by both unsustainable extraction of groundwater (in some places also by extraction of oil and gas), and by levees and other flood management practices that prevent accumulation of sediments from compensating for the natural settling of deltaic soils.[18] Total human-caused subsidence in the Rhine-Meuse-Scheldt delta (Netherlands) is estimated at 3-4 m (10-13 ft), over 3 m (10 ft) in urban areas of the Mississippi River Delta ( New Orleans), and over 9 m (30 ft) in the Sacramento-San Joaquin River Delta.[19] On the other hand, post-glacial isostatic rebound causes relative sea level fall around the Hudson Bay in Canada and the northern Baltic.[20]

The Atlantic is set to warm at a faster pace than the Pacific. This has consequences for Europe and the U.S. East Coast, which received a sea level rise 3-4 times the global average.[21] The downturn of the Atlantic meridional overturning circulation (AMOC) has been also tied to extreme regional sea level rise on the US Northeast Coast.[22]

There are broadly two ways of modelling sea level rise and making future projections. In one approach, scientists use process-based modelling, where all relevant and well-understood physical processes are included in a global physical model. An ice-sheet model is used to calculate the contributions of ice sheets and a general circulation model is used to compute the rising sea temperature and its expansion. A disadvantage of this method is that not all relevant processes might be understood to a sufficient level, but it can predict non-linearities and long delays in the response which studies of the recent past will miss.

In the other approach, scientists use semi-empirical techniques that use geological data from the past to determine likely sea level responses to a warming world in addition to some basic physical modelling.[3] These semi-empirical sea level models rely on statistical techniques, using relationships between observed past (contributions to) global mean sea level and global mean temperature.[24] This type of modelling was partially motivated by most physical models in previous literature assessments by the Intergovernmental Panel on Climate Change (IPCC) having underestimated the amount of sea level rise compared to observations of the 20th century.[16]

In its fifth assessment report (2013) the Intergovernmental Panel on Climate Change (IPCC) estimated how much sea level is likely to rise in the 21st century based on different levels of greenhouse gas emissions. These were conservative projections based on well-known factors which contribute to sea level rise, but exclude other processes which are less well understood. If emissions remain very high, the IPCC projected sea level would rise by 50-98 cm (- in).[16] In August 2020 scientists reported that observed ice-sheet losses in Greenland and Antarctica were tracking worst-case scenarios of those IPCC projections.[25][26][27][28] In 2021, the IPCC Sixth Assessment Report had barely changed its worst-case scenario (updating it to 0.6-1 m), whereas most other reports since 2020 have increased their upper estimates to at least 2 m in the very high emissions scenario.[5]

Other attempts have been made to include more physical processes and to develop models that can project sea level rise using paleoclimate data. This typically led to higher estimates of sea level rise.[29][30][31] A 2016 study led by Jim Hansen concluded that based on past climate change data, sea level rise could accelerate exponentially in the coming decades, with a doubling time of 10, 20 or 40 years, respectively, raising the ocean by several metres in 50, 100 or 200 years.[31] However, Greg Holland from the National Center for Atmospheric Research, who reviewed the study, noted: "There is no doubt that the sea level rise, within the IPCC, is a very conservative number, so the truth lies somewhere between IPCC and Jim."[32]

In addition, one 2017 study's scenario, assuming high fossil fuel use for combustion and strong economic growth during this century, projects sea level rise of up to 130 cm (4 ft 3 in) on average-and an extreme scenario with as much as 190 cm (6 ft 3 in), by 2100. This could mean rapid sea level rise of up to 19 mm (3⁄4 in) per year by the end of the century. The study also concluded that the Paris climate agreement emissions scenario, if met, would result in a median 52 cm ( in) of sea level rise by 2100.[33][34]

The Fourth (2017) National Climate Assessment (NCA) of the United States found that it is very likely sea level will rise between 30 and 130 cm (1.0-4.3 feet) in 2100 compared to the year 2000. A rise of 2.4 m (8 feet) is physically possible under a high emission scenario but the authors were unable to say how likely. This worst-case scenario can only come about with a large contribution from Antarctica; a region that is difficult to model.[35]

The possibility of a collapse of the West-Antarctic ice sheet and subsequent rapid sea level rise was suggested back in the 1970s.[29] For instance, Mercer published a study in 1978 predicting that anthropogenic carbon dioxide warming and its potential effects on climate in the 21st century could cause a sea level rise of around 5 m (15 ft) from melting of the West Antarctic ice-sheet alone.[36][29]

In 2019, a study projected that in low emission scenario, sea level will rise 30 cm by 2050 and 70 cm by 2100, relative to the level in 2000. In high emission scenario, it will be roughly 35 cm by 2050 and 110 cm by 2100. There is the probability that the rise will be beyond 2 metres by 2100 in the high emission scenario, which would cause displacement of 187 million people. Long before then, current projections of sea level rise for 2050 will generate an intense rise in the frequency of coastal flooding (a baseline of four "moderate" flooding events per year in the US), even without storms and/or heavy rainfall.[37][38][39]

In September 2019 the Intergovernmental Panel on Climate Change published a report about the impact of climate change on the oceans including sea level rise. It found that if humanity will drastically reduce Greenhouse gas emission in the next decades the problem will be tough but manageable. If the rise in emission will continue the problem will become unmanageable.[40] As of 2022 the rise has continued unabated.

In February 2021, researchers suggested that past projections for global sea level rise by 2100 reported by the IPCC were conservative, and that sea levels will rise more than previously expected.[41] In 2022, NOAA published a detailed Sea Level Rise Technical Report suggesting a rise of between 0.6 and 2.1 m with high confidence.[6]

High-end 21st-century sea level rise Edit

Sea level rise by 2100 that is much higher than the likely range of projection by the IPCC Sixth Assessment Report (AR6) is possible. In particular, AR6 models do not take into consideration many positive feedback loops that would lead to accelerated melting over time. AR6 does offer a speculative narrative about how more extreme melting could occur. It would probably involve a high warming scenario, in which urgent climate action is not taken and strong warming continues.[42] This could lead to a faster-than-projected collapse of marine ice shelves and the abrupt, widespread onset of marine ice cliff instability (a process in which ice cliffs collapse under their own weight) and ice sheet instability (a positive feedback loop that leads to runaway melting) in Antarctica, and a faster than projected ice loss in Greenland including reduced albedo as its ice melts.[42] Other processes in Antarctica such as hydrofracturing (in which meltwater collects in ice sheet fractures, forcing them open), increased contact of warm ocean water with ice shelves due to climate change induced ocean circulations changes[43][44][45] or changes in the weather over Antarctica leading to lower precipitation and ice deposition, could all be contributing factors.[45] The combination of such processes could lead to sea level rise as high as 2.3 metres by 2100.[42]

There is a widespread consensus among climate scientists that sea level rise lags well behind the temperature increase that triggers it, and that substantial long-term sea level rise will continue for centuries to come even if the temperature stabilizes.[46] Models are able to reproduce paleo records of sea level rise, which provides confidence in their application to long-term future change.[16]: 1189

Both the Greenland ice sheet and Antarctica have tipping points for warming levels that could be reached before the end of the 21st century. Crossing such tipping points would mean that ice-sheet changes are potentially irreversible: a decrease to pre-industrial temperatures may not stabilize the ice sheet once the tipping point has been crossed.[47] Quantifying the exact temperature change for which this tipping point is crossed remains controversial. For Greenland, estimates roughly range between 1 and 4 °C (2 to 7 °F) above pre-industrial.[47][16] As of 2020, the lower of these values has already been passed. A 2021 analysis of sub-glacial sediment at the bottom of a 1.4 km Greenland ice core finds that the Greenland ice sheet melted away at least once during the last million year. This strongly suggests that its tipping point is below the 2.5 °C maximum positive temperature excursion over that period, and is therefore within the lower half of its range of estimates.[48][49] Melting of the Greenland ice sheet would contribute 4-7.5 m (13- ft) of sea level rise.[8]

A 2013 study estimated that each degree of temperature rise translates to a 2.3 m (7 ft 7 in) commitment to sea level rise within the next 2,000 years.[50] More recent research, especially into Antarctica, indicates that this is probably a conservative estimate and that the true long-term sea level rise might be higher.[35] Warming beyond the 2 °C (3.6 °F) target potentially leads to rates of sea level rise dominated by ice loss from Antarctica. Continued carbon dioxide emissions from fossil fuel sources could cause additional tens of metres of sea level rise, over the next millennia, and the available fossil fuel on Earth is even enough to ultimately melt the entire Antarctic ice sheet, causing about 58 m (190 ft) of sea level rise.[51] After 500 years, sea level rise from thermal expansion alone may have reached only half of its eventual level, which models suggest may lie within ranges of 0.5-2 m (- ft).[52]

In the next 2,000 years the sea level is predicted to rise by 2-3 metres if the temperature rise peaks at 1.5 degrees, by 2-6 metres if it peaks at 2 degrees and by 19-22 metres if it peaks at 5 degrees.[5]: SPM-28  If temperature rise stops at 2 degrees or at 5 degrees, the sea level would still continue to rise for about 10,000 years. In the first case it will reach 8-13 metres above pre-industrial level, and in the second 28-37 metres.[53]

The three main reasons warming causes global sea level to rise are: oceans expand, ice sheets lose ice faster than it forms from snowfall, and glaciers at higher altitudes also melt. Sea level rise since the start of the 20th century has been dominated by retreat of glaciers and expansion of the ocean, but the contributions of the two large ice sheets (Greenland and Antarctica) are expected to increase in the 21st century.[3] The ice sheets store most of the land ice (∼99.5%), with a sea-level equivalent (SLE) of 7.4 m (24 ft 3 in) for Greenland and 58.3 m (191 ft 3 in) for Antarctica.[2]

Each year about 8 mm (5⁄16 in) of precipitation (liquid equivalent) falls on the ice sheets in Antarctica and Greenland, mostly as snow, which accumulates and over time forms glacial ice. Much of this precipitation began as water vapor evaporated from the ocean surface. Some of the snow is blown away by wind or disappears from the ice sheet by melt or by sublimation (directly changing into water vapor). The rest of the snow slowly changes into ice. This ice can flow to the edges of the ice sheet and return to the ocean by melting at the edge or in the form of icebergs. If precipitation, surface processes and ice loss at the edge balance each other, sea level remains the same. However scientists have found that ice is being lost, and at an accelerating rate.[55][56]

Most of the additional heat trapped in the Earth's climate system by climate change is stored in oceans. They store more than 90% of the extra heat and act as a buffer against the effects of climate change. The heat needed to raise an average temperature increase of the entire world ocean by 0.01 °C would increase the atmospheric temperature by approximately 10 °C.[57] Thus, a small change in the mean temperature of the ocean represents a very large change in the total heat content of the climate system.

When the ocean gains heat, the water expands and sea level rises. The amount of expansion varies with both water temperature and pressure. For each degree, warmer water and water under great pressure (due to depth) expand more than cooler water and water under less pressure.[16]: 1161  This means that cold Arctic Ocean water will expand less compared to warm tropical water. Because different climate models have slightly different patterns of ocean heating, they do not agree fully on the predictions for the contribution of ocean heating on sea level rise.[58] Heat gets transported into deeper parts of the ocean by winds and currents, and some of it reaches depths of more than 2,000 m (6,600 ft).[59]

Considering an increase in average global temperature of 2 °C above preindustrial levels, and not considering the potential contributions from ice-sheet processes with limited agreement (low confidence) among modeling approaches, the probability of exceeding 0.5 m rise of sea level globally (0.7 m along the CONUS coastline) by 2100 is about 50%. With 3-5 °C of warming under high emissions pathways, this probability rises to >80% to >99%.[60]

The large volume of ice on the Antarctic continent stores around 70% of the world's fresh water.[61] The Antarctic ice sheet mass balance is affected by snowfall accumulations, and ice discharge along the periphery. Under the influence of global warming, melt at the base of the ice sheet increases. Simultaneously, the capacity of the atmosphere to carry precipitation increases with temperature so that precipitation, in the form of snowfall, increases in global and regional models. The additional snowfall causes increased ice flow of the ice sheet into the ocean, so that the mass gain due to snowfall is partially compensated.[62] Snowfall increased over the last two centuries, but no increase was found in the interior of Antarctica over the last four decades.[63] Based on changes of Antarctica's ice mass balance over millions of years, due to natural climate fluctuations, researchers concluded that the sea-ice acts as a barrier for warmer waters surrounding the continent. Consequently, the loss of sea ice is a major driver of the instability of the entire ice sheet.[63]

Different satellite methods for measuring ice mass and change are in good agreement, and combining methods leads to more certainty about how the East Antarctic Ice Sheet, the West Antarctic Ice Sheet, and the Antarctic Peninsula evolve.[64] A 2018 systematic review study estimated that ice loss across the entire continent was 43 gigatons (Gt) per year on average during the period from 1992 to 2002, but has accelerated to an average of 220 Gt per year during the five years from 2012 to 2017.[65] Most of the melt comes from the West Antarctic Ice Sheet, but the Antarctic Peninsula and East Antarctic Ice Sheet also contribute. The sea level rise due to Antarctica has been estimated to be 0.25 mm per year from 1993 to 2005, and 0.42 mm per year from 2005 to 2015. All datasets generally show an acceleration of mass loss from the Antarctic ice-sheet, but with year-to-year variations.[2]

A May 2021 study projected that limiting global warming to 1.5 °C would reduce the land ice contribution to sea level rise by 2100 from 25 cm to 13 cm (from 10 to 6 in.) compared to current mitigation pledges, with glaciers responsible for half the sea level rise contribution.[66] The physical uncertainty of the Antarctic contribution was more significant than the uncertainty due to the choice of mitigation pathway.[66]

East Antarctica Edit

The world's largest potential source of sea level rise is the East Antarctic Ice Sheet, which holds enough ice to raise global sea levels by 53.3 m (174 ft 10 in).[67] The ice sheet has historically been considered to be relatively stable and has therefore attracted less scientific attention and observations compared to West Antarctica.[63] A combination of satellite observations of its changing volume, flow and gravitational attraction with modelling of its surface mass balance suggests the overall mass balance of the East Antarctic Ice Sheet was relatively steady or slightly positive for much of the period 1992-2017.[65] A 2019 study, however, using different methodology, concluded that East Antarctica is losing significant amounts of ice mass. The lead scientist Eric Rignot told CNN: "melting is taking place in the most vulnerable parts of Antarctica ... parts that hold the potential for multiple metres of sea level rise in the coming century or two."[63]

Methods agree that the Totten Glacier has lost ice in recent decades in response to ocean warming[68][69] and possibly a reduction in local sea ice cover.[70] Totten Glacier is the primary outlet of the Aurora Subglacial Basin, a major ice reservoir in East Antarctica that could rapidly retreat due to hydrological processes.[30] The global sea level potential of 3.5 m (11 ft 6 in) flowing through Totten Glacier alone is of similar magnitude to the entire probable contribution of the West Antarctic Ice Sheet.[71] The other major ice reservoir on East Antarctica that might rapidly retreat is the Wilkes Basin which is subject to marine ice sheet instability.[30] Ice loss from these outlet glaciers is possibly compensated by accumulation gains in other parts of Antarctica.[65]

West Antarctica Edit

Even though East Antarctica contains the largest potential source of sea level rise, it is West Antarctica that currently experiences a net outflow of ice, causing sea levels to rise. Using different satellites from 1992 to 2017 shows melt is increasing significantly over this period. Antarctica as a whole has caused a total of 7.6 ± 3.9 mm (19⁄64 ± 5⁄32 in) of sea level rise. Considering the mass balance of the East Antarctic Ice Sheet which was relatively steady, the major contributor was West Antarctica.[65] Significant acceleration of outflow glaciers in the Amundsen Sea Embayment may have contributed to this increase.[72] In contrast to East Antarctica and the Antarctic Peninsula, temperatures on West Antarctica have increased significantly with a trend between 0.08 °C (0.14 °F) per decade and 0.96 °C (1.73 °F) per decade between 1976 and 2012.[73]

Multiple types of instability are at play in West Antarctica. One is marine ice sheet instability, where the bedrock on which parts of the ice sheet rest is deeper inland.[74] This means that when a part of the ice sheet melts, a thicker part of the ice sheet is exposed to the ocean, which may lead to additional ice loss. Secondly, melting of the ice shelves, the floating extensions of the ice sheet, leads to a process named the Marine Ice Cliff Instability. Because they function as a buttress to the ice sheet, their melt leads to additional ice flow (see animation one minute into video). Melt of ice shelves is accelerated when surface melt creates crevasses and these crevasses cause fracturing.[29]

The Thwaites and Pine Island glaciers have been identified to be potentially prone to these processes, since both glaciers bedrock topography gets deeper farther inland, exposing them to more warm water intrusion into the grounding zone.[75][76] With continued melt and retreat they contribute to raising global sea levels.[77][78] The Thwaites glacier itself will cause a rise of sea level by 65 centimetres if it will completely collapse, but this can also destabilize other glaciers in west Antarctica.[79] [76] The Thwaites Ice Shelf can collapse in three to five years which can destabilize the entire Thwaites glacier.[80]

The melting of these two glaciers had accelerated at the beginning of the 21st century. It can destabilize the entire West Antarctic Ice Sheet. However, the process will probably not be finished in this century.[81] Most of the bedrock underlying the West Antarctic Ice Sheet lies well below sea level.[30] A rapid collapse of the West Antarctic Ice Sheet could raise sea level by 3.3 m (10 ft 10 in).[82][83]

Most ice on Greenland is part of the Greenland ice sheet which is 3 km (10,000 ft) at its thickest. The rest of the ice on Greenland is part of isolated glaciers and ice caps. The sources contributing to sea level rise from Greenland are from ice sheet melting (70%) and from glacier calving (30%). Dust, soot, and microbes and algae living on parts of the ice sheet further enhance melting by darkening its surface and thus absorbing more thermal radiation; these regions grew by 12% between 2000 and 2012, and are likely to expand further.[85] Average annual ice loss in Greenland more than doubled in the early 21st century compared to the 20th century.[86] Some of Greenland's largest outlet glaciers, such as Jakobshavn Isbræ and Kangerlussuaq Glacier, are flowing faster into the ocean.[87][88]

A study published in 2017 concluded that Greenland's peripheral glaciers and ice caps crossed an irreversible tipping point around 1997, and will continue to melt.[89][90] The Greenland ice sheet and its glaciers and ice caps are the largest contributor to sea level rise from land ice sources (excluding thermal expansion), combined accounting for 71 percent, or 1.32 mm per year during the 2012-2016 period.[91][92]

A study published in 2020 estimated that the Greenland Ice Sheet had lost a total of 3,902 gigatons (Gt) of ice between 1992 and 2018, corresponding to a contribution to sea level rise of 10.8 mm. The sea level rise due to the Greenland Ice Sheet has generally increased over time, rising from 0.07 mm per year between 1992 and 1997 to 0.68 mm per year between 2012 and 2017.[93]

Estimates on future contribution to sea level rise from Greenland range from 0.3 to 3 m (1 to 10 ft), for the year 2100.[85] By the end of the century, it can contribute 2-10 centimetres annually.[94] The contribution of the Greenland ice sheet on sea level over the next couple of centuries can be very high due to a self-reinforcing cycle (a so-called positive feedback). After an initial period of melting, the height of the ice sheet will have lowered. As air temperature increases closer to the sea surface, more melt starts to occur. This melting may further be accelerated because the color of ice is darker while it is melting. There is a threshold in surface warming beyond which a partial or near-complete melting of the Greenland ice sheet occurs.[95] Different research has put this threshold value as low as 1 °C (2 °F), and definitely 4 °C (7 °F), above pre-industrial temperatures.[96][16]: 1170  A 2021 analysis of sub-glacial sediment at the bottom of a 1.4 km Greenland ice core finds that the Greenland ice sheet melted away at least once during the last million year, and therefore strongly suggests that its tipping point is below the 2.5 °C maximum positive temperature excursion over that period.[48][49]

Less than 1% of glacier ice is in mountain glaciers, compared to 99% in Greenland and Antarctica. Still, mountain glaciers have contributed appreciably to historical sea level rise and are set to contribute a smaller, but still significant fraction of sea level rise in the 21st century.[97] The roughly 200,000 glaciers on earth are spread out across all continents.[98] Different glaciers respond differently to increasing temperatures. For instance, valley glaciers that have a shallow slope retreat under even mild warming. Every glacier has a height above which there is net gain in mass and under which the glacier loses mass. If that height changes a bit, this has large consequences for glaciers with a shallow slope.[99]: 345  Many glaciers drain into the ocean and ice loss can therefore increase when ocean temperatures increase.[98]

Observational and modelling studies of mass loss from glaciers and ice caps indicate a contribution to sea level rise of 0.2-0.4 mm per year, averaged over the 20th century.[100] Over the 21st century, this is expected to rise, with glaciers contributing 7-24 cm (3- in) to global sea levels.[16]: 1165  Glaciers contributed around 40% to sea level rise during the 20th century, with estimates for the 21st century of around 30%.[2]

Sea ice melt contributes very slightly to global sea level rise. If the melt water from ice floating in the sea was exactly the same as sea water then, according to Archimedes' principle, no rise would occur. However melted sea ice contains less dissolved salt than sea water and is therefore less dense: in other words although the melted sea ice weighs the same as the sea water it was displacing when it was ice, its volume is still slightly greater. If all floating ice shelves and icebergs were to melt sea level would only rise by about 4 cm ( in).[101]

Humans impact how much water is stored on land. Building dams prevents large masses of water from flowing into the sea and therefore increases the storage of water on land. On the other hand, humans extract water from lakes, wetlands and underground reservoirs for food production leading to rising seas. Furthermore, the hydrological cycle is influenced by climate change and deforestation, which can lead to further positive and negative contributions to sea level rise. In the 20th century, these processes roughly balanced, but dam building has slowed down and is expected to stay low for the 21st century.[102][16]: 1155

Sea level changes can be driven either by variations in the amount of water in the oceans, the volume of the ocean or by changes of the land compared to the sea surface. Over a consistent time period, conducting assessments can source contributions to sea level rise and provide early indications of change in trajectory. This type of surveillance can inform plans of prevention.[104] The different techniques used to measure changes in sea level do not measure exactly the same level. Tide gauges can only measure relative sea level, whilst satellites can also measure absolute sea level changes.[17] To get precise measurements for sea level, researchers studying the ice and the oceans on our planet factor in ongoing deformations of the solid Earth, in particular due to landmasses still rising from past ice masses retreating, and also the Earth's gravity and rotation.[2]

Since the launch of TOPEX/Poseidon in 1992, an overlapping series of altimetric satellites has been continuously recording the sea level and its changes.[105] Those satellites can measure the hills and valleys in the sea caused by currents and detect trends in their height. To measure the distance to the sea surface, the satellites send a microwave pulse which reflects on the ocean's surface and record the time it takes to return. Microwave radiometers correct the additional delay caused by water vapor in the atmosphere. Combining these data with the precisely known location of the spacecraft determines the sea-surface height to within a few centimetres (about one inch).[106] Current rates of sea level rise from satellite altimetry have been estimated to be 3.0 ± 0.4 millimetres (1⁄8 ± 1⁄64 in) per year for the period 1993-2017.[107] Earlier satellite measurements were previously slightly at odds with tide gauge measurements. A small calibration error for the Topex/Poseidon satellite was eventually identified as having caused a slight overestimation of the 1992-2005 sea levels, which masked in the satellite measurements the ongoing sea level rise acceleration that was visible in the tide gauge timeseries.[108]

Satellites are useful for measuring regional variations in sea level, such as the substantial rise between 1993 and 2012 in the western tropical Pacific. This sharp rise has been linked to increasing trade winds, which occur when the Pacific Decadal Oscillation (PDO) and the El Niño-Southern Oscillation (ENSO) change from one state to the other.[110] The PDO is a basin-wide climate pattern consisting of two phases, each commonly lasting 10 to 30 years, while the ENSO has a shorter period of 2 to 7 years.[111]

The global network of tide gauges is another important source of sea-level observations. Compared to the satellite record, this record has major spatial gaps but covers a much longer period of time.[113] Coverage of tide gauges started primarily in the Northern Hemisphere, with data for the Southern Hemisphere remaining scarce up to the 1970s.[113] The longest running sea-level measurements, NAP or Amsterdam Ordnance Datum established in 1675, are recorded in Amsterdam, the Netherlands.[114] In Australia record collection is also quite extensive, including measurements by an amateur meteorologist beginning in 1837 and measurements taken from a sea-level benchmark struck on a small cliff on the Isle of the Dead near the Port Arthur convict settlement in 1841.[115]

This network was used, in combination with satellite altimeter data, to establish that global mean sea-level rose 19.5 cm ( in) between 1870 and 2004 at an average rate of about 1.44 mm/yr (1.7 mm/yr during the 20th century).[116] Data collected by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia show that the global mean sea level currently rises by 3.2 mm (1⁄8 in) per year, at double the average 20th century rate.[117][118] This is an important confirmation of climate change simulations which predicted that sea level rise would accelerate in response to climate change.

Some regional differences are also visible in the tide gauge data. Some of the recorded regional differences are due to differences in the actual sea level, while other are due to vertical land movements. In Europe for instance, considerable variation is found because some land areas are rising while others are sinking. Since 1970, most tidal stations have measured higher seas, but sea levels along the northern Baltic Sea have dropped due to post-glacial rebound.[119]

Current and future sea level rise is set to have a number of impacts, particularly on coastal systems. Such impacts include higher and more frequent high-tide and storm-surge flooding, increased coastal erosion, inhibition of primary production processes, more extensive coastal inundation, changes in surface water quality and groundwater characteristics. This is projected in turn to increase loss of property and coastal habitats, increased flood risk and potential loss of life, loss of non-monetary cultural resources and values, impacts on agriculture and aquaculture through decline in soil and water quality, and loss of tourism, recreation, and transportation functions.[9]: 356  Many of these impacts are detrimental. Owing to the great diversity of coastal environments; regional and local differences in projected relative sea level and climate changes; and differences in the resilience and adaptive capacity of ecosystems, sectors, and countries, the impacts will be highly variable in time and space. River deltas in Africa and Asia and small island states are particularly vulnerable to sea level rise.[120]

In addition to rising sea level, other effects of climate change that can heavily impact the influence on populations. This includes, for example, loss of coastal ecosystems such as corals due to ocean warming or increasing extreme precipitations caused by climate change. Coastal flooding impacts are exacerbated by land use changes such as urbanisation or deforestation of low-lying coastal zones. Regions that are already vulnerable to the rising sea level also struggle with coastal flooding washing away land and altering the landscape.[121] People in these areas struggle increasingly because of these different effects of climate change. Climate change influenced storms also create greater frequency of coastal flooding. Addressing the flooding issues that a region, city, or country is experiencing will be based on the efforts of the affected country. Without much effort these coastal regions could continuously degrade and thus greatly affect the size and influence of a country.

Globally tens of millions of people will be exposed in the latter decades of the century if greenhouse gases are not reduced drastically. Many coastal areas have large population growth, which results in more people at risk from sea level rise. The rising seas pose both a direct risk: unprotected homes can be flooded, and indirect threats of higher storm surges, tsunamis and king tides. Asia has the largest population at risk from sea level with countries such as Bangladesh, China, India, Indonesia, and Vietnam having very densely populated coastal areas.[122] The effects of displacement are very dependent on how successful governments will be in implementing defenses against the rising sea, with concerns for the poorest countries such as sub-Saharan countries and island nations.[123]

A 2019 study found that the number of people exposed to sea level rise during the 21st century is three times higher that was previously thought. By 2050, 150 million will be under the water line during high tide and 300 million will live in zones with floodings every year. By the year 2100, those numbers differ sharply depending on the emission scenario. In a low emission scenario, 140 million will be under water during high tide and 280 million will have flooding each year. In high emission scenario, the numbers arrive to 540 million and 640 million respectively. Seventy per cent of them are from eight countries in Asia: China, Bangladesh, India, Indonesia, Thailand, Vietnam, Japan, Philippines.[124][125]

A 2020 review of 33 publications found that "most global estimates are in the order of tens or hundreds of millions of people exposed to coastal inundation and coastal flooding for different timeframes and scenarios" due to sea level rise.[126]

The long-term cumulative effects of rising sea levels pose a serious threat in coastal areas. Coastal areas are sensitive to rising sea levels, changes in the frequency and intensity of storms, increased precipitation, and rising ocean temperatures. Ten percent of the world's population live in coastal areas that are less than 10 metres (33 ft) above sea level. Furthermore, two thirds of the world's cities with over five million people are located in these low-lying coastal areas.[127] In total, approximately 600 million people live directly on the coast around the world.[128] Using remote laser scanning called LiDAR to measure elevation on the Earth's surface, researchers found that in the year 2021, 267 million people worldwide lived on land less than 2 metres above sea level and that with a 1-metre sea level rise and zero population growth, that number could increase to 410 million people.[129][130]

Populations that move from the coasts because of the effects of rising sea levels could be impacted by loss of livelihoods and could become a heavy strain on the regions or cities that they come to inhabit.[131] Further, both their original government or the receiving countries may lack or withhold resources to help these climate migrants, which compounds their level of poverty.

Present effects Edit

Sea level rise favors chronic flooding at high tide, as evidenced e.g. in the US East Coast.[132] Similarly, Florida, which is extremely vulnerable to climate change, is already experiencing substantial nuisance flooding and king tide flooding.[133] One other area in danger is Venice which has experienced significant flooding. The city is located on islands in the delta of the Po and Piave rivers. Sea level rise causes an increase in frequency and magnitude of floodings in the city that already spent more than $6 billion on the flood barrier system.[134][135]

Food production in coastal areas is affected by rising sea levels as well. Due to flooding and salt water intrusion into the soil, the salinity of agricultural lands near the sea increases, posing problems for crops that are not salt-resistant. Furthermore, salt intrusion in fresh irrigation water poses a second problem for crops that are irrigated. Newly developed salt-resistant crop variants are currently more expensive than the crops they are set to replace.[136] The farmland in the Nile Delta is affected by salt water flooding,[137] and there is now more salt in the soil and irrigation water in the Red River Delta and the Mekong Delta in Vietnam.[136] Bangladesh and China are affected in a similar way, particularly their rice production.[138]

Rising seas has also been tied to an increased risk from tsunamis, potentially affecting coastal cities in the Pacific and Atlantic Oceans.[10]

Future effects Edit

Future sea level rise could lead to potentially catastrophic difficulties for shore-based communities in the next centuries: for example, millions of people will be affected in cities such as Miami, Rio de Janeiro, Osaka and Shanghai if following the current trajectory of 3 °C (5.4 °F).[11] The Egyptian city Alexandria faces a similar situation, where hundreds of thousands of people living in the low-lying areas may already have to be relocated in the coming decade.[137] However, modest increases in sea level are likely to be offset when cities adapt by constructing sea walls or through relocating.[141]

Nonpartisan think tank Resources for the Future describes Miami as "the most vulnerable major coastal city in the world" to damages associated with storm-related coastal flooding and sea level rise.[142] Storm surge will be one of the important disasters caused by sea level rise in the future that can cause the largest loss of life and property in the world's coastal areas. Storm surges have been affected in recent years by rising sea levels, which have increased in frequency and intensity. For example, one of the most severely affected areas is New York City, where study simulations show that the impact of sea level rise on the New York area will be reduced from 100-year flooding to 19-68 years by 2050 and 40-60 years by 2080.[143]

Atolls, low islands and low-lying coastal areas on islands are particularly vulnerable to sea level rise. Possible impacts include coastal erosion, flooding and salt intrusion into soils and freshwater. None are more vulnerable than small island nations, particularly those with population concentrations on atolls. Atolls on average reach three to six feet above sea level.[144] This type of island is a final stage in the geologic history of an island of volcanic origin (all volcanic islands usually become an atoll, eventually). With climate change causing sea levels rise, the process of atoll formation has sped up.

Since atolls are low-lying islands, they are vulnerable to rising waters or storms covering them in water. Atolls are vital because they are the home to many distinct cultures and sovereign nations. As ocean water prematurely covers atolls, saltwater can intrude into drinking water supplies and undermine the ecosystems that the population utilizes to survive.[145] Sea level rise has the potential to devastate tourism and local economies; a sea level rise of 1.0 m (3 ft 3 in) would cause partial or complete inundation of 29% of coastal resorts in the Caribbean. A further 49-60% of coastal resorts would be at risk from resulting coastal erosion.[146] It is difficult to assess how much of past erosion and floods have been caused by sea level change, compared to other environmental events such as hurricanes. Adaptation to sea level rise is costly for small island nations as a large portion of their population lives in areas that are at risk.[147]

Maldives, Tuvalu, and other low-lying countries are among the areas that are at the highest level of risk. At current rates, sea level would be high enough to make the Maldives uninhabitable by 2100.[148][149] The Island nation of Fiji is being impacted by sea level rise.[150] Five of the Solomon Islands have disappeared due to the combined effects of sea level rise and stronger trade winds that were pushing water into the Western Pacific. [151] Countries becoming uninhabitable could exacerbate the humanitarian crisis of climate refugees.[152]

Of interest is how the rising sea level will affect children in these communities. Children without stability at home and their communities can experience a variety of issues in their development. Already, children in small island states are encountering hampered access to food and water, displacement, and resulting mental and social disorders from these stressors.[153]

In the case all islands of an island nation become uninhabitable or completely submerged by the sea, the states themselves would also become dissolved. Once this happens, all rights on the surrounding area (sea) are removed. This area can be significant as rights extend to a radius of 415 kilometres (224 nautical miles) around the entire island state. Any resources, such as fossil oil, minerals and metals, within this area can be freely dug up by anyone and sold without needing to pay any commission to the (now dissolved) island state.[154]

Coastal ecosystems are facing drastic changes as a consequence of rising sea levels. Many systems might ultimately be lost when sea levels rise too much or too fast. Some ecosystems can move land inward with the high-water mark, but many are prevented from migrating due to natural or artificial barriers. This coastal narrowing, sometimes called 'coastal squeeze' when considering human-made barriers, could result in the loss of habitats such as mudflats and marshes.[14][155]

The mangrove ecosystem is one of the ecosystems affected by rising sea levels. It is an ecological whole composed of mangrove plants growing in and around the mudflats of the tropical coast. Its ecological value is high because it is an ideal home for many species. In recent years, mangroves have been moving inland, but their success depends on various environmental information such as topography and geology. The warmer the climate, the bigger they grow. The mangrove's breathing roots or pneumatophores might grow to be half a metre tall.[156][157] Mangroves and tidal marshes adjust to rising sea levels by building vertically using accumulated sediment and organic matter. If sea level rise is too rapid, they will not be able to keep up and will instead be submerged.[158] More specifically, if the rate of mangrove deposition does not keep up with sea level rise, the key to the extinction of the mangrove ecosystem is the relationship between the rate of inland migration and the rate of sea level rise. If sea levels rise faster than the mangroves can move to land, this can lead to the loss of ecosystems.[159] The ability of mangroves to survive sea level rise events depend on their ability to migrate inland.[157] As both ecosystems protect against storm surges, waves and tsunamis, losing them makes the effects of sea level rise worse.[160][161] Human activities, such as dam building, may restrict sediment supplies to wetlands, and thereby prevent natural adaptation processes. The loss of some tidal marshes is unavoidable as a consequence.[162]

When seawater reaches inland, problems related to contaminated soils may occur. Also, fish, birds, and coastal plants could lose parts of their habitat.[12] Coral, important for bird and fish life, needs to grow vertically to remain close to the sea surface in order to get enough energy from sunlight. It has so far been able to keep up the vertical growth with the rising seas, but might not be able to do so in the future.[163] In 2016, it was reported that the Bramble Cay melomys, which lived on a Great Barrier Reef island, had probably become extinct because of inundation due to sea level rises.[164] This report was confirmed by the federal government of Australia when it declared the Bramble Cay melomys extinct as of February 2019, making this species the first known mammal to go extinct as a result of sea level rise.[165]

Adaptation options to sea level rise can be broadly classified into retreat, accommodate and protect. Retreating is moving people and infrastructure to less exposed areas and preventing further development in areas that are at risk. This type of adaptation is potentially disruptive, as displacement of people might lead to tensions. Accommodation options are measurements that make societies more flexible to sea level rise. Examples are the cultivation of food crops that tolerate a high salt content in the soil and making new building standards which require building to be built higher and have less damage in the case a flood does occur. Finally, areas can be protected by the construction of dams, dikes and by improving natural defenses.[13][166] In more detail, the existing problems are divided into two parts: one is water pollution, and the other is storm surges and floods.[167] Besides, storm surges and flooding can be instantaneous and devastating to cities, and some coastal areas have begun investing in storm water valves to cope with more frequent and severe flooding during high tides.[167]

These adaptation options can be further divided into hard and soft. Hard adaptation relies mostly on capital-intensive human-built infrastructure and involves large-scale changes to human societies and ecological systems. Because of its large scale, it is often not flexible. Soft adaptation involves strengthening natural defenses and adaptation strategies in local communities and the use of simple and modular technology, which can be locally owned. The two types of adaptation might be complementary or mutually exclusive.[166][168]

Sea trade is the dominant form of resource and good trade throughout the world. When talking about the rising sea level there is the possibility for major issues to arise for sea-based trade and the ports that are utilized. What is also of importance for these ports is that we do not yet know how the rising sea level will continue to impact them over time.[169] A variety of factors play into the investment of seaports for this means. Factors that are important for seaports in reference to the rising sea level are where will the important trade ports be in the future, can we alter and protect the ports that are currently being used, how much is needed to protect trade without wasting time or money. The rising sea level for seaports is a concern, but is hard to decipher what changes need to be made since sea levels do not rise at the same rate all over the world.[170]

Cutting greenhouse gas emissions (or climate change mitigation) can stabilize sea level rise rates beyond 2050, but can not prevent sea levels from rising. Thus, mitigation gives more time for adaptation and it leaves more options open, such as nature-based solutions.[171]: 3-127

Many countries are developing concrete plans for adaptation. An example is the extension of the Delta Works in the Netherlands, a country that sits partially below sea level and is subsiding.[172] In 2008, the Dutch Delta Commission, advised in a report that the Netherlands would need a massive new building program to strengthen the country's water defenses against the rising sea for the following 190 years. This included drawing up worst-case plans for evacuations. The plan also included more than €100 billion in new spending through to the year 2100 for precautionary measures, such as broadening coastal dunes and strengthening sea and river dikes. The commission said the country must plan for a rise in the North Sea up to 1.3 m (4 ft 3 in) by 2100 and plan for a 2-4 m (7-13 ft) rise by 2200.[173]

To address the sea level rise threat in Bangladesh, the Bangladesh Delta Plan 2100 has been launched in 2018.[174][175] As of 2020, it was seen falling short of most of its initial targets.[176] The progress is being monitored.[177]

U.S. coastal cities conduct beach nourishment, also known as beach replenishment, where mined sand is trucked in and added, in addition to other adaptation measures such as zoning, restrictions on state funding, and building code standards.[178][179] Some island nations, such as the Republic of Maldives, Kiribati and Tuvalu are considering international migration of their population in response to rising seas. Moving to different countries is not an easy solution, as those who move need to have a steady income and social network in their new country. It might be easier to adapt locally by moving further inland and increasing sediment supply needed for natural erosion protection.[180] In the island nation of Fiji, residents are restoring coral reefs and mangroves to protect themselves against flooding and erosion, which is estimated to be more cost-efficient than building sea-walls.[181]

Adaptation to sea level rise often has to account for other environmental issues, such as land-subsidence or habitat destruction. In 2019, the president of Indonesia, Joko Widodo, declared that the city of Jakarta is sinking to a degree that requires him to move the capital to another city.[182] A study conducted between 1982 and 2010 found that some areas of Jakarta have been sinking by as much as 28 cm (11 inches) per year[183] due to ground water drilling and the weight of its buildings, and the problem is now exacerbated by sea level rise. However, there are concerns that building in a new location will increase tropical deforestation.[184][185] Other so called sinking cities, such as Bangkok or Tokyo, are vulnerable to these compounding subsidence with sea level rise.[186]

Understanding past sea level is an important guide to current and future changes. In the recent geological past, thermal expansion from increased temperatures and changes in land ice are the dominant reasons of sea level rise. The last time that the Earth was 2 °C (3.6 °F) warmer than pre-industrial temperatures was 120 thousand years ago, when warming because of changes in the amount of sunlight due to slow changes in the Earth's orbit caused the Eemian interglacial; sea levels during that warmer interglacial were at least 5 m (16 ft) higher than now.[187] The Eemian warming was sustained over a period of thousands of years, and the magnitude of the rise in sea level implies a large contribution from the Antarctic and Greenland ice sheets.[16]: 1139  Further into the past, a report by the Royal Netherlands Institute for Sea Research states that, around three million years ago, levels of carbon dioxide in the Earth's atmosphere similar to today's levels increased temperature by two to three degrees Celsius and melted one third of Antarctica's ice sheets. This in turn caused sea-levels to rise 20 metres over their present values.[188]

Since the last glacial maximum about 20,000 years ago, the sea level has risen by more than 125 metres (410 ft), with rates varying from less than a mm/year during the pre-industrial era to 40+ mm/year when major ice sheets over Canada and Eurasia melted. Rapid disintegration of these ice sheets led to so called ' meltwater pulses', periods during which sea level rose rapidly. The rate of rise started to slow down about 8,200 years before present; the sea level was then almost constant in the last 2,500 years, before the recent rising trend that started at the end of the 19th century or in the beginning of the 20th.[189]

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# data[].attributes.attachment_link.description
Tide gauge measurements show that the current global sea level rise began at the start of the 20th century. Between 1901 and 2018, the globally averaged sea level rose by 15-25 cm (6-10 in).[1] More precise data gathered from satellite radar measurements reveal an accelerating rise of 7.5 cm (3 in) from 1993 to 2017,[2] : 1554  for an average rate of 3.1 cm ( in) per decade.

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《기상이변이 연례행사처럼 일어나고 있다. 세계 곳곳에서 100년 또는 200년 만이라는 폭우 폭설 가뭄이 자주 되풀이되고 있다. 일부 기상학자는 기상이변에 대한 개념이 바뀌어야 한다고 주장한다. 90년대 이후 발생한 기상이변은 지구온난화와 열대지역의 해수온도가 높아지는 엘니뇨 현상 등이 원인이라는 것이다. 따라서 전 지구적인 대책을 마련하지 않으면 어떤 재앙이 닥칠지 모른다고 경고하고 있다. 아울러 기상이변이 자주 반복됨에 따라 이에 대한 대비책도 과거와는 달라져야 한다는 주장도 설득력을 얻어가고 있다.》

▼실태-원인과 전망▼

▽매년 계속되는 '이변'〓'2000년 폭설, 2001년 극심한 가뭄, 2002년 사상 초유의 폭우와 태풍.'

최근 2, 3년간 세계적으로 기상이변이 계속되고 있다. 한국에서는 올 8월 한달 동안에 과거 1년 동안 내릴 비가 한꺼번에 쏟아졌으며 햇빛이 비추는 일조시간이 평년의 절반도 안 되는 등 이상 현상이 속출했다.

기상청에 따르면 8월 1∼31일 대관령과 강릉 지역에 내린 강수량은 각각 1236.4㎜, 1137㎜로 연평균 강수량(1283㎜)에 육박했다. 특히 강릉에는 31일 하루동안 870.5㎜가 쏟아져 1904년 근대적인 기상관측이 시작된 이래 최고기록을 수립했다.

반면 지난해에는 한반도에 태풍이 한 개도 상륙하지 않았다. 태풍 상륙에 대비해 충주댐 대청댐 등 유역 면적이 넓은 일부 댐의 물을 미리 뺀 한국수자원공사는 저수량 부족으로 곤욕을 치렀다. 또 2001년 3∼5월에는 사상 최악의 가뭄이 찾아왔다. 이 기간 동안 강수량은 지역에 따라 평년의 11.8∼73.6%에 불과했다.

한편 2000년 겨울(12월∼2001년 2월)에는 폭설이 내려 지역마다 적설량 최고 기록을 갈아치웠다.

▽지구온난화와 엘니뇨가 범인〓1990년대 이후 세계적으로 기상이변이 속출하고 있는 원인에 대해 기상학자들은 지구온난화와 엘니뇨 현상을 꼽는다.

산업화 공업화 등으로 인한 이산화탄소 배출량의 증가, 산림파괴 등으로 지구가 온실처럼 따뜻해지면서 기온이 상승하는 '지구온난화' 현상을 주범으로 꼽는 전문가가 많다.

기상청 박정규 기후예측과장은 "기온상승으로 대기에 유입되는 수증기 양이 늘어나면 이를 소모하기 위해 폭우 태풍 등이 자주 발생한다"고 설명했다.

기후변화에 관한 정부간 협의회(IPCC) 보고서에 따르면 20세기, 100년동안 지구의 평균기온은 0.6도 상승했다. 이는 수천만년 전부터 19세기까지 100년에 0.01도 상승해온 것에 비하면 엄청나게 큰 상승폭이다. 특히 한반도 기상에 영향을 크게 미치는 몽골과 중국 북부 내륙지역의 기온 상승 폭은 20세기, 100년동안 2∼4도에 달한다.

연세대 대기과학과 김정우 교수는 "한반도의 겨울철 날씨 패턴이던 삼한사온이 없어지고 매년 4∼5월에 찾아오던 황사가 3∼4월로 한달 앞당겨진 것도 이 같은 기온 변화와 무관하지 않다"고 말했다.

대기와 해양의 흐름이 합작해 만드는 자연현상인 엘니뇨 또한 기상이변의 중요한 원인으로 꼽힌다.

엘니뇨는 남미 해안에서 중태평양에 이르는 넓은 열대 태평양 지역의 해수면 온도가 평균적인 해수면 온도보다 높아지는 현상이다.

특히 엘니뇨 감시구역인 동태평양 적도지역 페루 연안의 월평균 해수면 온도가 예년에 비해 0.5도 이상 높은 현상이 6개월 이상 지속될 때를 엘니뇨 현상이라고 부른다.

정확한 원인은 규명되지 않았지만 엘니뇨 현상이 나타날 때마다 페루 등 세계 곳곳에서 홍수 해일 가뭄 등 기상이변이 발생하고 있다.

▽기상이변 고착화〓기상학자들은 지구온난화가 당분간 멈추지 않을 것이며 이로 인해 지구상 곳곳에 극심한 가뭄과 폭설 폭우가 내리는 기상이변도 계속 될 것이라고 입을 모은다.

특히 지역에 따라 건조한 지역은 더욱 건조해지고 상습적인 수해지역은 물난리가 더욱 심해지는 양극화 현상이 심화될 전망이다.

김 교수는 "최근의 기후변화 흐름을 볼 때 한반도에는 적어도 앞으로 4∼5년간 비정상적인 기후가 지속될 가능성이 높다"면서 새로운 기후형태로 고착화될 가능성을 배제하지 않았다.

기상이변이 해마다 되풀이되자 기후변화에 걸맞는 정책을 수립해야 한다는 지적도 제기되고 있다.

서울대 대기과학과 강인식교수는 "단순한 기상예보 중심의 기상행정에서 벗어나 기후변화를 예측하는 데 많은 인력과 장비를 투자해야 한다"면서 "기후가 변하고 있기 때문에 댐건설 치수사업 등 대규모 건설사업을 추진할 때 과거 기후자료가 아닌 미래예측자료를 사용하고 기후영향평가를 제도화해야 한다"고 말했다. 강 교수는 "국민들도 매년 과거와는 비교가 안될 정도로 큰 자연재해가 발생하고 있는 현상에 대한 대비책을 정부에만 떠넘길 것이 아니라 재해보험에 가입하는 등 자체적인 재해방지시스템을 갖춰야 한다"고 덧붙혔다.

이호갑기자 gdt@donga.com

▼세계 기상이변-대응▼

1900년부터 세계적으로 총 28회의 엘니뇨 현상이 나타났다. 이 같은 기상이변이 생길 때마다 세계에는 크고 작은 자연재해가 발생했다.

특히 1997년과 98년에는 극심한 엘니뇨 현상이 나타나 지구촌에 엄청난 인명과 재산 피해가 났다.

기상청에 따르면 이 기간중 홍수 한파 가뭄 폭염 폭설 해일 등 55건의 기상이변이 일어나 세계적으로 7만8000여명이 사망했다. 이재민은 350만여명, 재산 피해는 55억달러에 이르렀다.

올해 역시 5월부터 약한 엘니뇨 현상이 나타나기 시작해 8월중 유럽 동남아시아 중국 미국 등지에 극심한 홍수 가뭄 등 기상이변이 나타났다.

특히 체코 오스트리아 독일 루마니아 등 유럽 중부지역에는 100년 만에 폭우가 쏟아져 체코의 수도 프라하와 오스트리아의 음악도시 잘츠부르크가 침수되는 초유의 사태가 벌어졌다.

러시아도 8월 중순 10년 만에 대홍수가 발생해 93명이 숨지고 수만명의 이재민이 발생했다.

미국은 1732년 이후 최악의 가뭄 때문에 시달리고 있다. 특히 캐롤라이나주는 8월 한달 동안 비가 전혀 내리지 않는 등 5년 내리 심각한 가뭄이 발생했다.

중국 역시 8월15일부터 20일까지 태풍이 남부 해안지방을 강타해 900여명이 숨졌고 수만명의 이재민이 생겼다.

이 밖에 베트남, 방글라데시, 태국 등지도 홍수 등 자연 재해로 많은 피해를 보았다.

미국 유럽 등 기상선진국은 1980년부터 기상이변의 주요 원인으로 알려진 엘니뇨 현상 등 세계의 기후변화에 대해 본격적인 연구를 시작했다.

특히 미국은 1987년 기후법을 채택해 매년 예산의 일부를 반드시 기후변화에 대한 연구에쓰도록 하고 있다.

유럽 18개국은 공동출자해 유럽중기예보센터(ECHWF) 산하에 해들리 기후센터를 만들었다. 이 센터에는 기상 전문가 100여명이 배치돼 이상기후에 관한 연구를 심층적으로 진행하고 있다. 일본도 2001년 기상청 기후예측과 인력을 30명에서 50여명으로 늘렸으며 초대형 슈퍼 컴퓨터를 도입해 기후변화 연구에 힘을 쏟고 있다.

이호갑기자 gdt@donga.com

▼국내 수해방지 시스템▼

중앙재해대책본부에 따르면 4일 오전 현재 태풍 '루사'로 인한 피해는 인명만 200여명, 재산은 2조원을 넘어섰다.

기상재해 피해가 해마다 눈덩이처럼 커지고 있다. 92년 315억원 규모에 머물던 기상재해 피해액은 98년 1조5815억원으로 1조원대를 처음으로 돌파했으며 2000년 6454억원으로 잠시 줄었다가 폭우와 가뭄, 폭설 등 기상이변이 나타난 지난해에는 다시 1조2561억원으로 늘었다.

해마다 피해복구비로 쏟아 부은 액수는 이보다 더욱 많다.

삼성 지구환경연구소 정예모(鄭禮模) 연구원은 "공장가동 중단과 교통마비에 따른 손실, 농작물 피해와 농산물 가격 폭등 요인 등을 감안하면 피해 규모는 공식집계의 3∼4배에 이를 것"이라고 말했다.

전문가들은 이 같은 악순환을 끊으려면 정부가 임시복구와 보상보다는 예방, 즉 '치수 인프라'를 구축하는 데 중점을 두어야 한다고 지적한다.

정 연구원은 "피해액의 10%만이라도 치수방재 프로젝트 등에 과감하게 예방투자를 했더라면 거푸 피해를 보는 일은 막을 수 있었을 것"이라고 강조했다.

집중호우 때마다 큰 피해를 보았던 경기 파주시 문산읍은 그간 배수펌프장 신설과 증설, 경보시스템 구축 등을 통해 올해 피해가 전무했다. 반면 경남 합천군이 지난달 집중호우 때 낙동강 제방 2곳이 터져 수몰된 지 20여일 만에 또다시 재난을 당한 것은 이런 주장을 뒷받침한다.

전문가들은 또 여름철 국지성 집중호우가 최근 수년간 이어지면서 '한국적 기상 현상'으로 자리잡은 만큼 이제는 이에 대한 장기 대책이 필요한 때라고 입을 모은다. 이들은 현재 전국적으로 재해예방 관련 예산이 연중 얼마나 집행되는지조차 모르는 실정이라고 비판했다. 각 자치단체와 부처별로 계획이 세워지고 예산이 집행되는 탓이다. 이러다 보니 재해예방을 총괄 지휘하는 '사령부'도 없어 효율적인 재해예방과 예산집행이 이루어지지 않고 있다는 것이다.

건설기술연구원 김이호(金利鎬) 수환경연구팀장은 "궁극적으로는 기상이변이 지구 온난화 등 환경파괴에 따른 현상인 만큼 환경보호, 이산화탄소배출량 감축 등 에너지 저소비형 사회·경제체제를 구축해야 할 것"이라고 지적했다.

서영아기자 sya@donga.com

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속출하는 기상이변...재앙은 계속된다

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《기상이변이 연례행사처럼 일어나고 있다. 세계 곳곳에서 100년 또는 200년 만이라는 폭우 폭설 가뭄이 자주 되풀이되고 있다. 일부 기상학자는 기상이변에 대한 개념이 바뀌어야 한다고 주장한다. 90년대 이후 발생한 기상이변은 지구온난화와 열대지역의 해수온도가 높아지는 엘니뇨 현상 등이 원인이라는 것이다. 따라서 전 지구적인 대책을 마련하지 않으면 어떤 재앙이 닥칠지 모른다고 경고하고 있다.

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https://climate.nasa.gov/

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Climate Change: Vital Signs of the Planet

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Home - Climate Change: Vital Signs of the Planet

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Vital Signs of the Planet: Global Climate Change and Global Warming. Current news and data streams about global warming and climate change from NASA.

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https://www.science.org.au/learning/general-audience/science-climate-change/2-how-has-climate-changed

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1. https://www.wri.org/insights/6-ways-climate-changed-over-past-decade

2. https://www.wri.org/insights/extreme-weather-whats-climate-change-got-do-it

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Most scientific reports on climate look at changes that have occurred since the pre-industrial era, or since record-keeping began. But even looking back at the past decade, it's clear that our world today is very different from the world of 2010. Analyzing data on greenhouse gas (GHGs) concentrations, temperature rise, sea level rise and more reveal troubling trends.

But first, the good news:

There were some important bright spots for climate over the past 10 years. At the start of the decade, projections by the International Energy Agency (IEA) suggested that world's emissions trajectory put it on course for a catastrophic 6˚C of warming by the end of the century, significantly higher than the 1.5-2 degrees C (2.7-3.6 degrees F) scientists recommend staying under to avoid the worst climate impacts. This year's IEA report projects warming of 2.9-3.4˚C with current policies, a testament to the very different emissions trajectory the world forged this past decade.

The growth of renewables also far exceeded expectations. The price of solar PV dropped 81% since 2009. By 2017, the majority of new power-generating capacity added worldwide came from renewables.

And the recent groundswell of citizen action is unprecedented, with millions around the world taking to the streets, engaging in climate action and demanding greater action from decision-makers.

While these examples and others show remarkable progress, overall our climate system is making it clear that we are not acting quickly enough. Here are several notable trends we can see just over the past decade:

1) Carbon Dioxide Emissions from Fossil Fuels Grew 10%

The Global Carbon Project reported earlier this month that global carbon dioxide emissions from fossil fuels and cement are on track to climb to a record high in 2019. While global emissions growth plateaued between 2014 and 2016, it was short-lived: Emissions from fossil fuels grew 1.5% in 2017, 2.1% in 2018 and are projected to grow another 0.6% in 2019.

The latest climate science suggests that our best chance of limiting warming to 1.5-2 degrees C will require emissions to peak no later than 2020 and drop to net-zero by mid-century. A critical question is whether we'll see signs next year of emissions peaking and declining afterwards.

A decade's worth of UNEP Emissions Gap Reports document the growing gap between where emissions are headed and where they need to be. Even if countries fully implement their current climate commitments, the research shows we'll still face an emissions gap in 2030 of 32 GtCO2e (about twice the size of China and India's combined emissions) for the 1.5 degrees C goal, and 15 GtCO2e for the 2 degrees C goal.

2) Global Average Temperature Increased

In 2010, global average temperature was 0.88˚C (1.6˚F) above pre-industrial levels. Temperature increase in 2019 is shaping up to be about 1.1 degrees C (2˚F) above pre-industrial levels.

Against this backdrop of climbing temperatures, countries around the world also agreed this past decade to limit warming to well below 2 degrees C, and ideally 1.5 degrees C. A definitive report from the Intergovernmental Panel on Climate Change (IPCC) found that the world will face severe climate impacts even with 1.5 degrees of warming, and the effects get significantly worse with 2 degrees. For example, under 1.5 degrees C of warming, it is very likely that the Arctic will have one sea-ice-free summer every 100 years; at 2 degrees C, the frequency increases to at least one every 10 years.

3) Concentrations of Carbon Dioxide in the Atmosphere Exceeded 400 Parts Per Million (PPM)

Temperatures increase as the concentration of carbon dioxide in the atmosphere rises. Not too long ago, the idea of surpassing 400 parts per million (ppm) of carbon dioxide, a symbolic threshold which Earth has not experienced for millions of years, felt quite far off. In 2010, carbon dioxide concentrations at the Mauna Loa Observatory in Hawaii were 390 ppm on average. By 2018, they were well beyond the 400 ppm threshold, with measurements reaching 408 ppm. (For context, pre-industrial concentrations of carbon dioxide were 280 ppm.)

Between 2000 and 2009, the average growth rate of carbon dioxide concentrations at Mauna Loa was 2 ppm. Between 2010 and 2018, this figure grew to 2.4 ppm/yr. In 2018, the growth rate was 2.9 ppm/yr.

4) Seas Rose More than 1.6 Inches

Global mean sea level rise was roughly 3.3 millimeters (mm) per year (0.13 inch/yr) between 1993 and the present. This trend accelerated significantly this past decade: Between 2010 and 2018, sea level rise grew to about 4.4 mm/yr (0.17 inch/yr), rising almost 2 inches overall in the past decade. In 2018, global mean sea level was the highest in the satellite record.

Eight of the world's 10 largest cities are located in vulnerable coastal areas. Seas rising by even a couple of inches leads to more frequent high-tide flooding, storm surges pushing further inland, and devastating risks to homes, habitat and infrastructure.

5) Ice Reached Record Lows

Sea ice extent is smallest in September every year. The rate of September sea ice decline has been 13% per decade relative to the 1981-2010 average. During this past decade, Arctic sea ice minimum reached its lowest level since at least 1979, the year record-keeping began.

Ice sheets in Greenland and Antarctica have also been losing mass, with an acceleration of loss in just the last decade.

Glaciers around the world are also losing ice, accelerating with each passing decade. Glacier melt grew from 460 milliliters of liquid water in the 1990s to 500 in the 2000s to 850 milliliters in 2010-2018.

Ice loss can lead to rising seas. It can also change the ocean's surface reflectivity, exposing dark waters that absorb more solar radiation - much like a dark shirt on a hot, sunny day - in turn leading to greater warming and a positive feedback loop.

6) Extreme Weather Became More Frequent and Severe

This past decade has been marked by devastating extreme events, including heat waves on land and in the ocean, record rainfall and flooding, massive fires and heat-charged hurricanes. Communities around the world are already living with the impacts of just 1 degrees C (1.8 degrees F) of warming; our climate will only become deadlier and more devastating with every additional fraction of a degree of temperature rise.

Recent research confirms that extreme weather is getting more frequent and severe. The probability of drought has increased substantially in the Mediterranean region due to human-caused emissions. Extreme heat waves are increasing with further warming. And there is significant evidence that human-induced warming has resulted in the increased frequency, intensity and/or amount of heavy precipitation events. In 2017, Hurricanes Harvey, Irma, Jose and Maria all reached unprecedented rapid intensification, with Irma setting a record for sustained winds of 185 miles/hr. Harvey and Maria had record-setting rainfall, with warmer water temperatures fueling extreme precipitation.

At the same time, the science of attribution, looking at how much climate change increased the odds of any one particular event occurring, has advanced remarkably over this past decade. Important assessments include those from the National Academies and the Bureau of the American Meteorological Society, which published eight reports explaining how climate change may have affected extreme events from 2011 to 2018. Among many other examples, the reports found that climate change increased the odds of intense heat waves in northeast Asia in 2018 and in southern Europe in 2017, exceptional precipitation in Mid-Atlantic states in 2018, and an East African drought in 2017, which contributed to food insecurity. In addition, several international research programs came together to develop the World Weather Attribution project to analyze the role of climate change in extreme events.

Will 2020 Be the Decade for Action on Climate Change?

If we were to document the change in these climate indicators from the pre-industrial era, the trends would of course be even more stark. But even in a decade's time, Earth has transformed.

It's time for policy to change at a speed that is commensurate with the rate of changing planetary vital signs. Let's hope that in 2030, we will look back and call the past 10 years a decade of climate action.

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6 Ways the Climate Changed Over the Past Decade

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Most scientific reports on climate look at changes since the pre-industrial era or since record-keeping began. But even looking at the past decade, it's clear that our world today is very different from the world of 2010, thanks to climate change.

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(1) https://www.c2es.org/content/extreme-weather-and-climate-change/

(2)
https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature

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One of the most visible consequences of a warming world is an increase in the intensity and frequency of extreme weather events. The National Climate Assessment finds that the number of heat waves, heavy downpours, and major hurricanes has increased in the United States, and the strength of these events has increased, too.

A measure of the economic impact of extreme weather is the increasing number of billion-dollar disasters, which is shown below. The map shows all types of weather disasters, some of which are known to be influenced by climate change (floods, tropical storms) and some for which a climate influence is uncertain (tornadoes).

Billion-Dollar Extreme Weather Events, 2000-2023

Click on any circle to learn about one of the billion-dollar weather events, or any state to learn about billion-dollar droughts, between January 2000 and June 2023. Source: National Oceanic and Atmospheric Administration's National Climatic Data Center. The Top 10 costliest events are listed at the bottom of this page, along with a description of major U.S. droughts since 2000.

NOAA calculates total, direct costs - both insured and uninsured - including physical damage to residential, commercial, and government buildings, material assets within buildings, public infrastructure, vehicles and boats, offshore energy platforms, and agricultural assets, as well as business interruption losses and disaster restoration and wildfire suppression costs. These estimates do not account for losses to natural capital, health care related costs, or values associated with loss of life.

Climate change is expected to worsen the frequency, intensity, and impacts of some types of extreme weather events. For example, sea level rise increases the impacts of coastal storms and warming can place more stress on water supplies during droughts.

That's why many cities, state, and businesses are taking steps to prepare for more extreme weather.

Learn more about the links between climate change and:

Weathering the Next Storm: A Closer Look at Business Resilience examines how companies are preparing for climate risks and what is keeping them from doing more. It also suggests strategies for companies and cities to collaborate to strengthen climate resilience. It updates the groundbreaking report, Weathering the Storm, Building Business Resilience to Climate Change, which provided a baseline for how companies were assessing their climate vulnerabilities.

Hurricane Ian

September 2022

115.2

152

Cat. 4 Hurricane near Cayo Costa, Fla., with sustained winds of 150 mph.

Hurricane Andrew
August 1992

$58.6

61

Cat. 5 hurricane hit Fla. and later La. as a Cat. 3. High winds damaged or destroy over 125,000 homes and left at least 160,000 people temporarily homeless.

U.S. Drought/Heatwave
Summer 1998

$52.8

454

1988 drought across a large portion of the U.S. with very severe losses to agriculture and related industries. Combined direct and indirect deaths (i.e., excess mortality) due to heat stress estimated at 5,000.

Midwest Flooding
Summer 1993

$44.9

48

The costliest non-tropical, inland U.S. flood event on record. Severe, widespread flooding in central U.S. due to persistent heavy rain. Extensive damage to agriculture, infrastructure, homes, and businesses in many areas across several states.

Data source: NOAA, 2023. Descriptions edited for brevity.

Table 2: U.S. Drought Events Since 2000

2022

$22.9

Severe drought impacted many Western and Central states. Large reservoirs across the West including Lake Mead, Lake Powell, Lake Oroville, and Shasta Lake, among others continue to be depleted. Excess heat caused more than 100 deaths.

Ariz., Calif., Colo., Ida., Mont., N.M., Nev., Ore., Utah, Wash., Wyo.

2006

Severe drought affected crops, caused wildfires and low streams and rivers in the Great Plains and portions of the South and far West.

Ala., Ark., Colo., Fla., Ga., Iowa, Kan., La., Minn., Miss., Mo., Mont., N.D., N.M., Neb., Okla., S.D., Texas, Wyo.

2005

Severe localized drought caused significant crop losses, especially for corn and soybeans.

Ark., Ill., Ind., Mo., Ohio, Wis.

Data source: NOAA, 2023. Descriptions edited for brevity.

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One of the most visible consequences of a warming world is an increase in the intensity and frequency of extreme weather events. The National Climate Assessment finds that the number of heat waves, heavy downpours, and major hurricanes has increased in the United States, and the strength of these events has increased, too.

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https://www.wri.org/insights/6-ways-climate-changed-over-past-decade

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https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature

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Earth's surface temperature has risen about 2 degrees Fahrenheit since the start of the NOAA record in 1880.

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https://www.climate.gov/news-features/climate-qa/why-did-earth%E2%80%99s-surface-temperature-stop-rising-past-decade,
https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature
https://m.dongascience.com/news.php?idx=48586

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Climate Change: Vital Signs of the Planet

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"Climate change" and "global warming" are often used interchangeably but have distinct meanings. Similarly, the terms "weather" and "climate" are sometimes confused, though they refer to events with broadly different spatial- and timescales.

Weather vs. Climate

"If you don't like the weather in New England, just wait a few minutes."

Weather refers to atmospheric conditions that occur locally over short periods of time-from minutes to hours or days. Familiar examples include rain, snow, clouds, winds, floods, or thunderstorms.

Climate, on the other hand, refers to the long-term (usually at least 30 years) regional or even global average of temperature, humidity, and rainfall patterns over seasons, years, or decades.

What is Global Warming?

Global warming is the long-term heating of Earth's surface observed since the pre-industrial period (between 1850 and 1900) due to human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth's atmosphere. This term is not interchangeable with the term "climate change."

Since the pre-industrial period, human activities are estimated to have increased Earth's global average temperature by about 1 degree Celsius (1.8 degrees Fahrenheit), a number that is currently increasing by more than 0.2 degrees Celsius (0.36 degrees Fahrenheit) per decade. The current warming trend is unequivocally the result of human activity since the 1950s and is proceeding at an unprecedented rate over millennia.

What is Climate Change?

Climate change is a long-term change in the average weather patterns that have come to define Earth's local, regional and global climates. These changes have a broad range of observed effects that are synonymous with the term.

Changes observed in Earth's climate since the mid-20th century are driven by human activities, particularly fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth's atmosphere, raising Earth's average surface temperature. Natural processes, which have been overwhelmed by human activities, can also contribute to climate change, including internal variability (e.g., cyclical ocean patterns like El Niño, La Niña and the Pacific Decadal Oscillation) and external forcings (e.g., volcanic activity, changes in the Sun's energy output, variations in Earth's orbit).

Scientists use observations from the ground, air, and space, along with computer models, to monitor and study past, present, and future climate change. Climate data records provide evidence of climate change key indicators, such as global land and ocean temperature increases; rising sea levels; ice loss at Earth's poles and in mountain glaciers; frequency and severity changes in extreme weather such as hurricanes, heatwaves, wildfires, droughts, floods, and precipitation; and cloud and vegetation cover changes.

Find Out More: A Guide to NASA's Global Climate Change Website

This website provides a high-level overview of some of the known causes, effects and indications of global climate change:

Evidence. Brief descriptions of some of the key scientific observations that our planet is undergoing abrupt climate change.

Causes. A concise discussion of the primary climate change causes on our planet.

Effects. A look at some of the likely future effects of climate change, including U.S. regional effects.

Vital Signs. Graphs and animated time series showing real-time climate change data, including atmospheric carbon dioxide, global temperature, sea ice extent, and ice sheet volume.

Earth Minute. This fun video series explains various Earth science topics, including some climate change topics.

Other NASA Resources

Goddard Scientific Visualization Studio. An extensive collection of animated climate change and Earth science visualizations.

Sea Level Change Portal. NASA's portal for an in-depth look at the science behind sea level change.

NASA's Earth Observatory. Satellite imagery, feature articles and scientific information about our home planet, with a focus on Earth's climate and environmental change.
Shutterstock credits: wandee007 (left), Amy Johansson (middle), Avatar_023 (right).

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Overview: Weather, Global Warming and Climate Change

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"Climate change" and "global warming" are often used interchangeably but have distinct meanings. Similarly, the terms "weather" and "climate" are sometimes confused, though they refer to events with broadly different spatial- and timescales. "If you don't like the weather in New England, just wait a few minutes."

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https://climate.nasa.gov/vital-signs/sea-level/

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Climate Change: Vital Signs of the Planet

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101 (± 4.0) mm

This is the "uncertainty margin," or the range from the mean (average) within which there is a high probability that the true number resides. For example, when we say global sea level has risen 101 mm +/- 4 mm, the true value has a high probability of being between 97 and 105 mm. The uncertainty margin exists both because of sea level variability (sea level above the first point in the time series) in the ocean and the accuracy with which we measure the individual values.

Key Takeaway:

Global sea levels are rising as a result of human-caused global warming, with recent rates being unprecedented over the past 2,500-plus years.

Sea level rise is caused primarily by two factors related to global warming: the added water from melting ice sheets and glaciers, and the expansion of seawater as it warms. The first graph tracks the change in global sea level since 1993, as observed by satellites.

The second graph, which is from coastal tide gauge and satellite data, shows how much sea level changed from about 1900 to 2018. Items with pluses (+) are factors that cause global sea level to increase, while minuses (-) are what cause sea level to decrease. These items are displayed at the time they were affecting sea level.

The data shown are the latest available, with a four- to five-month delay needed for processing.

* You now need to create an Earthdata account to access NASA's sea level data. Register here for free. Once logged in, click the "download data" button on this page to access the data.
NASA Sea Level Change

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Vital Signs of the Planet: Global Climate Change and Global Warming. Current news and data streams about global warming and climate change from NASA.

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https://earthobservatory.nasa.gov/world-of-change/global-temperatures

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Air temperatures on Earth have been rising since the Industrial Revolution. While natural variability plays some part, the preponderance of evidence indicates that human activities-particularly emissions of heat-trapping greenhouse gases-are mostly responsible for making our planet warmer.

According to an ongoing temperature analysis led by scientists at NASA's Goddard Institute for Space Studies (GISS), the average global temperature on Earth has increased by at least 1.1° Celsius (1.9° Fahrenheit) since 1880. The majority of the warming has occurred since 1975, at a rate of roughly 0.15 to 0.20°C per decade.

The maps above show temperature anomalies in five-year increments since 1880. (Click on the arrow to run the animation.) These are not absolute temperatures, but changes from the norm for each area. The data reflect how much warmer or cooler each region was compared to a base period of 1951-1980. (The global mean surface air temperature for that period was 14°C (57°F), with an uncertainty of several tenths of a degree.)

The image below shows global temperature anomalies in 2022, which tied for the fifth warmest year on record. The past nine years have been the warmest years since modern recordkeeping began in 1880.

As the maps show, global warming does not mean temperatures rise everywhere at every time by same rate. Temperatures might rise 5 degrees in one region and drop 2 degrees in another. For instance, exceptionally cold winters in one place might be balanced by extremely warm winters in another part of the world. Generally, warming is greater over land than over the oceans because water is slower to absorb and release heat ( thermal inertia). Warming may also differ substantially within specific land masses and ocean basins.

In the animation at the top of the page and in the bar chart below, the years from 1880 to 1939 tend to be cooler, then level off by the 1950s. Decades within the base period (1951-1980) do not appear particularly warm or cold because they are the standard against which other years are measured.

The leveling off of temperatures in the middle of the 20th century can be explained by natural variability and by the cooling effects of aerosols generated by factories, power plants, and motor vehicles in the years of rapid economic growth after World War II. Fossil fuel use also increased after the war (5 percent per year), boosting greenhouse gases. Cooling from aerosol pollution happened rapidly. In contrast, greenhouse gases accumulated slowly, but they remain in the atmosphere for a much longer time. According to former GISS director James Hansen, the strong warming trend of the past four decades likely reflects a shift from balanced aerosol and greenhouse gas effects on the atmosphere to a predominance of greenhouse gas effects after aerosols were curbed by pollution controls.

Why should we care about one or two degrees of global warming? After all, temperatures fluctuate by many degrees every day where we live.

The temperatures we experience locally and in short periods can fluctuate significantly due to predictable, cyclical events (night and day, summer and winter) and hard-to-predict wind and precipitation patterns. But the global temperature mainly depends on how much energy the planet receives from the Sun and how much it radiates back into space. The energy coming from the Sun fluctuates very little by year, while the amount of energy radiated by Earth is closely tied to the chemical composition of the atmosphere-particularly the amount of heat-trapping greenhouse gases.

A one-degree global change is significant because it takes a vast amount of heat to warm all of the oceans, the atmosphere, and the land masses by that much. In the past, a one- to two-degree drop was all it took to plunge the Earth into the Little Ice Age. A five-degree drop was enough to bury a large part of North America under a towering mass of ice 20,000 years ago.

Global temperature records start around 1880 because observations did not sufficiently cover enough of the planet prior to that time. The line plot above shows yearly temperature anomalies from 1880 to 2020 as recorded by NASA, NOAA, the Berkeley Earth research group, the Met Office Hadley Centre (United Kingdom), and the Cowtan and Way analysis. Though there are minor variations from year to year, all five records show peaks and valleys in sync with each other. All show rapid warming in the past few decades, and all show the last decade as the warmest.

The NASA GISS team chose the period of 1951-1980 as its baseline largely because the U.S. National Weather Service uses a three-decade period to define "normal" or average temperature. The GISS temperature analysis effort also began around 1980, so the most recent 30 years was 1951-1980. Their objective is to provide an estimate of temperature change that could be compared with predictions of global climate change in response to atmospheric carbon dioxide, aerosols, and changes in solar activity.

NASA's temperature analyses incorporate surface temperature measurements from more than 20,000 weather stations, ship- and buoy-based observations of sea surface temperatures, and temperature measurements from Antarctic research stations. These in situ measurements are analyzed using an algorithm that considers the varied spacing of temperature stations around the globe and urban heat island effects.

1. References

2. Hansen, J., et al. (2010). Global surface temperature change. Reviews of Geophysics, 48.

3. NASA Earth Observatory (2015, January 21) Why So Many Global Temperature Records?

4. NASA Earth Observatory (2010, June 3) Global Warming.

5. NASA Earth Observatory (2023, January 13) 2022 Tied for Fifth Warmest Year on Record.

6. NASA Goddard Institute for Space Studies (2023) GISS Surface Temperature Analysis (GISTEMP).

7. NOAA National Centers for Environmental Information (2022, January 10) Assessing the Global Climate in 2021.

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The average global temperature has increased by a little more than 1° Celsius (2° Fahrenheit) since 1880. Two-thirds of the warming has occurred since 1975.

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https://www.climate.gov/news-features/climate-qa/why-did-earth%E2%80%99s-surface-temperature-stop-rising-past-decade

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https://www.climate.gov/news-features/climate-qa/why-did-earth%E2%80%99s-surface-temperature-stop-rising-past-decade

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https://www.oxfam.org/en/press-releases/carbon-emissions-richest-1-percent-more-double-emissions-poorest-half-humanity

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he report assesses the consumption emissions of different income groups between 1990 and 2015 - 25 years when humanity doubled the amount of carbon dioxide in the atmosphere. It found :

Governments can tackle both extreme inequality and the climate crisis if they target the excessive emissions of the richest and invest in poor and vulnerable communities. For example, a recent study found that the richest 10 percent of households use almost half (45 percent) of all the energy linked to land transport and three quarters of all energy linked to aviation. Transportation accounts for around a quarter of global emissions today, while SUVs were the second biggest driver of global carbon emissions growth between 2010 and 2018.

"Governments must curb the emissions of the wealthy through taxes and bans on luxury carbon such as SUVs and frequent flights. Revenues should be invested in in public services and low carbon sectors to create jobs, and help end poverty," added Gore .

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Carbon emissions of richest 1 percent more than double the emissions of the poorest half of humanity | Oxfam International

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The richest one percent of the world’s population are responsible for more than twice as much carbon pollution as the 3.1 billion people who made up the poorest half of humanity during a critical 25-year period of unprecedented emissions growth.

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https://www.ucsusa.org/resources/global-warming-faq

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https://www.epa.gov/regulations-emissions-vehicles-and-engines/regulations-greenhouse-gas-emissions-passenger-cars-and

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https://www.ucsusa.org/resources/global-warming-faq

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https://www.science.org.au/learning/general-audience/science-climate-change/2-how-has-climate-changed

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https://scienceon.kisti.re.kr/srch/selectPORSrchTrend.do?cn=GT200602218

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동향 상세정보

2006-11-11

개발도상국이 지구온난화로 인한 충격에 적응하도록 돕는 노력은 '부적절하게 잘못된' 정책이라고 유엔의 보고서는 지적했다. 선진국가들은 이산화탄소 배출량을 감소하려고 하고 있지만 빈곤국가들이 그 결과에 어떻게 대처할 것인가에 대해서는 무시하고 있다. 이러한 논의는 유엔개발프로그램 (UNDP)의 인간발전보고서 2006(Human Development Report 2006)에 나타나 있다. 저자들은 농부들이 강수량에 작물을 의존하고 있지만 이러한 경향은 이미 예측할 수 없는 기후에 대처해야 한다고 주장했다. "희소성을 넘어서: 권력과 빈곤 그리고 전지구적 수자원의 위기(Beyond Scarcity: Power, Poverty and the Global Water Crisis)"라는 제목의 이 보고서는 지구온난화가 "인간발전의 전례없는 위협이 되고 있다"고 주장하고 있다.

이 보고서의 주저자인 케빈 와킨스(Kevin Watkins)는 피해우려가 높은 환경에서 살고 있는 사람들은 이미 변하는 환경에 적응해야 한다고 말했다. 그는 "아프리카의 동부지역에서 발생한 가뭄이 지구온난화와 연관되어 있다는 많은 증거가 제시되고 있다. 이러한 문제는 50년 뒤의 문제가 아니라 지금 발생하고 있는 문제"라고 말했다. 와킨스는 가장 피해를 입고 있는 지역이 한정된 수자원 기반시설을 갖고 있는 지역으로 사하라지역 남부 아프리카가 그 예가 될 수 있다고 지적하고 있다. 그는 "이러한 지역들은 관계시설능력을 갖고 있는 지역이 아니라 수자원을 보관할 수 있는 능력에 문제가 있는 지역"이라고 말했다. 그는 "사하라 남부 지역에 살고 있는 90% 이상의 사람들이 강우에 의존한 농경방법을 사용하고 있다. 그래서 강우량과 연관된 토양은 바로 빈곤과 연관되어 있다"고 덧붙였다. 그는 작물생산이 일부 지역에서 1/3까지 감소할 수 있다고 경고했다.

각 국가마다 그 결과는 다양하지만 이 보고서는 일부 광범위한 결과를 예상할 수 있다고 주장하고 있다:
- 농경과 농촌개발은 기후변화의 위험에 대해 무감각해질 수 있다
- 극단적인 빈곤과 영양실조는 수자원의 부족문제의 증가와 연관된다
- 좀더 극단적인 기후변화는 홍수와 가뭄의 위험을 증가시킨다
- 빙하의 수축과 해수면의 상승은 담수의 부족을 가져온다

산업화된 국가들은 대기로 뿜어내고 있는 온실가스의 양을 줄이기 위한 지구변화에 대응하는 이니셔티브를 실천하고 있기 때문에 개발도상국의 적응을 돕는 것은 그저 '파편적이고 일부'에 불과하다고 이 보고서는 주장하고 있다. 이 보고서는 국제적인 대응이 '완전히 부적절하다'고 주장하고 있다. 그 이유는 이 적응 프로젝트에 대한 진지한 투자가 이루어지지 않기 때문이다. 와킨스는 "적응의 문제는 유아적이고 너무 저발전의 상태이다. 교토의정서에 의한 지원금은 연간 2,000만 달러이다. 이것은 다자간 협상의 부분으로 어떠한 강조점도 없다"고 지적하고 있다. 그에 따르면 전세계환경설비(Global Environment Facility, GEF)를 통한 적응지원금은 앞으로 3년 동안 5,000만 달러이다. 와킨스는 "우리가 직면하고 있는 것은 지난 100년 동안 잠재적으로 아프리카의 인간발전에 있어서 최대의 실패이며 지금까지 국제사회가 제공한 자금은 7000만 달러"라고 말했다.

최근 지구온난화에 대응하기 위한 국제적인 협상은 나이로비에서 진행되고 있으며, 적응의 문제는 가장 우선의 문제이다. 케냐의 수도에서 이루어지고 있는 국제회의에서 유엔의 지구온난화에 대한 프레임워크 회의(UN Framework Convention on Climate Change, UNFCCC)가 발행한 보고서에서 지구온난화는 아프리카에서 심각한 위협이라고 보고 있다. 이 보고서는 왜 아프리카의 국가들을 지구온난화로부터 보호할 수 있는 경제와 기반시설이 매우 중요한가를 설명하고 있다. 다음 주에 있을 회의에서 적응의 문제에 관한 합의가 이루어질 것으로 보인다. 케빈 와킨스는 이 회의가 취약한 농촌지역에서 살고 있는 사람들에게 필요한 자금과 전략을 제공할 수 있을 것으로 희망하고 있다.

최근 잇달아 발표되고 있는 지구온난화 문제에 대한 정책보고서들은 현재 지구온난화가 정치-경제-사회적으로 긴급한 문제인가를 보여주고 있다. 이번 유엔개발프로그램이 발표한 정책 보고서는 지구온난화가 개발도상국과 빈곤국가에 미치는 위협과 그에 대한 방안을 논의하고 있다. 현재 온실가스 배출량 감소를 목표로 하고 있는 선진국 중심의 지구온난화 대응방안과 함께 지구온난화와 가스배출감소가 개발도상국과 빈곤국가에 미칠 수 있는 영향을 고려하고 있다. 이러한 정책보고서는 지구온난화와 책임 있는 산업국가에서의 정책개발에 큰 영향을 미칠 수 있을 것이다.

유엔개발프로그램이 발표한 관련 보고서는 다음을 참조:
http://hdr.undp.org/hdr2006/report.cfm

※ yesKISTI 참조

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[동향]UN, 지구온난화가 개발도상국에 미치는 영향에 관한 정책보고서

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개발도상국이 지구온난화로 인한 충격에 적응하도록 돕는 노력은 '부적절하게 잘못된' 정책이라고 유엔의 보고서는 지적했다. 선진국가들은 이산화탄소 배출량을 감소하려고 하고 있지만 빈곤국가들이 그 결과에 어떻게 대처할 것인가에 대해서는 무시하고 있다. 이러한 논의는 유엔개발프로그램 (UNDP)의 인간발전보고서 2006(Human Development Report 2006)에 나타나 있다. 저자들은 농부들이 강수량에 작물을 의존하고 있지만 이러한 경향은 이미 예측할 수 없는 기후에 대처해야 한다고 주장했다.

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https://www.ncei.noaa.gov/access/monitoring/monthly-report/global/202113

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그야말로 엎친 데 덮친 격이다. 전 세계가 코로나19 사태로 초유의 고통을 겪고 있는 가운데 산불과 폭우, 태풍 등 숨돌릴 틈도 없이 연이어 발생하고 있는 자연재해로 지구가 신음하고 있다.

국내의 경우 유래가 없는 긴 장마를 경험했고, 미 서부 지역은 산불로 인해 남한 의 5분의 1에 해당하는 면적이 잿더미로 변한 상황이다. 아시아는 또 어떤가. 끊임없이 이어지는 태풍들로 인해 수많은 인명피해와 천문학적인 손실을 입었다.

이처럼 전 세계에서 동시다발적으로 일어나고 있는 자연재해의 원인에 대해 대다수 전문가들은 '기후변화'를 주범으로 보고 있다. 기후변화의 속도가 최근 들어 더욱 빨라지면서 기상과 관련된 각종 재난을 일으키는 원인이 되고 있다는 것이다.

물론 기후변화의 심각성이 거론된 것은 어제오늘의 일이 아니다. 또한 기후변화에 맞서 전 세계가 동참 의지를 밝힌 것도 사실이다. 지난 2015년, 200여 개에 달하는 국가들이 파리기후변화협약을 맺고 온실가스 배출량을 단계적으로 감축하자고 약속한 것은 그 같은 의지를 보여준 사례다.

하지만 자국 이익만을 생각한 일부 국가들의 이기적인 행동과 코로나19 사태 등으로 인해 기후변화에 대응하고자 하는 인류의 노력은 별다른 결실을 얻지 못한 채 답보 상태에 머무르고 있다. 그리고 그런 상황을 틈타 기후변화의 속도는 더욱 가속화되고 있는 중이다.

그렇다면 앞으로 기후변화의 미래는 어떻게 진행될까? 지금으로서는 비관도 낙관도 시기상조라는 것이 대다수 전문가의 의견이다. 이들은 무엇보다도 과학적 통계 시스템을 기반으로 하여 기후변화가 어떤 영향을 미치고 있는지를 조사하는 것이 필요하다고 입을 모은다. 그런 과학적 조사 결과를 바탕으로 해야만 미래를 보다 정확하게 예측할 수 있기 때문이다.

환경 분야: 국내 온실가스 배출량 1990년 이후 약 2.37배 증가

환경부의 발표에 따르면 국내 온실가스 배출량은 지난 1990년 이후 26년 동안 약 2.37배가 증가한 것으로 나타났다. 그중 이산화탄소 배출량이 차지하는 비율은 1990년 86.1%에서 2016년 91.9%로 증가했다.

또한 2018년에 발간된 미국의 연례기후보고서를 살펴보면 2017년을 기준으로 세계 온실가스 배출량이 현대 대기 관측 사상 최고치를 기록한 것으로 파악됐다.

이는 화석에너지의 연소 등 빠르게 진행되는 산업화로 인해 대기 중의 이산화탄소 농도가 급속히 증가했기 때문이다. 이런 이유로 세계기상기구(WMO)와 국제연합환경계획(UNEP)은 이산화탄소를 지구 온난화의 주범이라고 공식적으로 선언한 상황이다.

온실가스 배출량이 증가함에 따라 북극의 지표면 온도도 1981년부터 2010년까지의 평균 온도보다 1.6℃가 상승했다. 또한 빙하 크기는 38년 동안 계속해서 감소하는 추세를 보여주었으며, 이에 따라 해수면 높이도 6년 연속 최고치를 달성한 상황이다.

국내 평균 기온이 높아지는 것도 어찌 보면 이 같은 추세에 기인하고 있다. 일기예보 전문업체인 케이웨더(KWeather)는 한반도가 아열대 기후로 변하고 있으며, 유엔 기후변화협의체(IPCC)에서 예상하는 것보다 더 빠르게 아열대로 진입할 가능성이 크다고 예측한 바 있다.

농업 분야: 배 재배는 줄고 아열대 과일은 매년 증가

기후변화로 이해 가장 타격을 받고 있는 분야는 농업이다. 4계절이 뚜렷했던 한반도의 기후는 어느새 열대성 기후로 변하고 있고, 이에 따라 곡물 및 과일 등의 재배지역도 과거와는 판이한 결과를 보여주고 있다.

달고 물이 많은 것으로 유명한 우리나라의 배가 대표적인 사례다. 농림축산식품부가 공개한 자료를 보면 2008년부터 2019년까지의 배 재배면적은 1만 8277ha에서 9616ha로 47.4%가 줄어든 것으로 나타났다.

또한 같은 기간 생산량도 47만 743톤에서 20만 732톤으로 무려 57.4%가 급감한 것으로 드러났다. 특히 국산 배의 주산지인 전남에서조차 생산량이 12만 7188톤에서 5만 582톤으로 60.2% 줄어든 것은 기후변화의 영향을 극명하게 보여주는 수치다.

반면에 참다래와 무화과, 그리고 망고 및 백향과 등 아열대 과일의 경우는 관련 통계가 작성된 2017년부터 지난해까지 3년간 매년 늘고 있는 추세다. 전체 재배면적은 50% 증가했고, 재배 농가수도 45.9% 급증했는데, 그중 망고의 재배면적이 가장 많이 증가했다.

이 같은 현상에 대해 농림축산식품부는 이상 기온으로 인해 지난 20년간 배의 개화 반응이 약 2일 정도 빨라진 점을 주목하고 있다. 또한 봄철 서리 등 냉해 피해 위험이 증가하면서 재배 적합지가 변동하고 있는 점도 배의 생산량이 감소한 이유로 판단하고 있다.

농촌진흥청 역시 '신농업 기후변화 기획보고서'를 통해 현재 기온보다 1.5℃ 상승하게 되면 2040년대의 한반도 기후에서는 고품질 배의 재배 적지가 급감하게 되고, 고랭지 배추 역시 90% 이상의 재배지가 감소할 것으로 예상하고 있다.

따라서 농업정책이 기후변화와 소비자 수요에 세밀하게 대응하지 못한다면, 농업의 미래는 불투명해질 수밖에 없다는 것이 대다수 전문가의 의견이다.

질병 분야: 코로나도 기후변화와 밀접한 관계가 있다

기후변화는 농업만큼이나 사람의 건강에 많은 영향을 미치는 것으로 알려져 있다. 그중에서도 지구온난화로 인해 자주 발생하는 폭염은 건강을 해치는 요인 중 가장 큰 요인이다.

기상청 발표에 따르면 올해 6월의 평균 일 최고기온은 28.0℃였고, 일 평균기온은 22.8℃인 것으로 파악됐다. 이는 지난 1973년 이래 최고 기록을 달성한 것으로서, 폭염일수도 2.0일에 달했다. 6월의 폭염일수가 2.0일인 것은 그동안의 6월 평균 폭염일수보다 1.4일이나 늘어난 것이다.

폭염은 열사병뿐 아니라 탈수 관련 합병증 등 광범위한 질병을 초래한다. 또 폭염은 만성 폐질환과 함께 심장이나 신장에 문제가 있는 환자들에게 악영향을 미친다. 기존 질환의 증상을 악화시키고 심지어는 정신질환에도 영향을 미치는 것으로 나타났다.

질병관리본부의 통계에 따르면 지난 2018년 한국에서 폭염과 관련한 발병자는 4526명이었고, 사망자도 48명에 이르는 것으로 조사됐다. 그러나 폭염으로 인한 간접적인 건강 영향이 반영되지 않은 점을 고려하였을 때 실제 사망자는 훨씬 더 많을 것으로 추정되고 있다.

기후변화의 직접적 요인인 폭염이 질병의 원인 중 하나라면 어린이는 기후변화에 따라 발생하는 질병의 직접적인 대상이라 할 수 있다. 면역력이나 체력이 성인에 비해 많이 떨어지는 만큼 기후변화에 적응하기 어렵기 때문이다.

세계보건기구(WHO)에 따르면, 기후변화로 인해 발생하는 질병의 88%는 5세 미만의 어린이에게 발생하고, 미국소아과학회에서는 2015년에 기후변화가 어린이들의 건강과 직결된다고 경고한 바 있다.

그 이유로 여름철 이상고온이 1세 미만 어린이들의 건강에 치명적인 위협을 줄 수 있고, 적절한 영양 공급을 막을 수 있다는 점을 들었다. 영양 공급의 경우 대기 중 이산화탄소의 농도 변화가 곡물의 단백질 함량을 낮출 수 있다는 것이 세계보건기구 측의 설명이다.

이 외에도 소두증을 유발하는 지카바이러스나 5세 미만 아동 사망에서 큰 비중을 차지하는 말라리아, 그리고 현재 전 세계를 공포의 도가니로 몰아넣고 있는 코로나19 등이 모두 기후변화가 미치는 영향 때문에 발생한 것으로 파악되고 있다.

얼핏 생각하면 코로나19 같은 전염병과 기후변화는 별다른 상관관계가 없는 것처럼 보이는 것이 사실이다. 그러나 조금만 더 그 속을 들여다보면 전염병과 기후변화는 상당히 밀접한 관계가 있음을 알 수 있다.

이는 온도가 상승하면서 질병이 퍼지는 데 적합한 환경을 만들었기 때문이다. 코로나바이러스만 해도 과거에는 깊은 밀림 속의 박쥐에서나 발견되었지만, 개발로 인해 밀림이 사라지고 온도는 따뜻해지면서 인간의 영역에까지 침범한 것으로 추정하고 있다.

에너지 분야: 여름철 열대야와 겨울철 한파로 에너지 소비 증가

에너지 부문에서는 폭염 및 열대야로 7월~8월 건물 부문 전력 소비량이 증가하여 아파트 정전 횟수가 증가했으며 1월~2월 사이에는 겨울철 한파로 인한 에너지 소비량이 증가한 것으로 나타났다.

전력 소비의 경우 지구온난화에 따라 여름철 냉방 전력 소비는 증가하고 있고, 겨울철 난방 전력 소비는 감소 추세에 있는 등 계절적 대비가 뚜렷하게 발생하고 있다. 따라서 2020년대 중반 무렵부터는 여름철 냉방에 의한 전력소비가 겨울철 난방에 의한 소비를 넘어설 것으로 추정되고 있다.

한편 원자력과 석탄 및 가스 발전, 그리고 수력 및 일부 태양력 발전의 경우 냉각 과정이 필수적이다. 그런데 기후변화에 의해 가뭄 발생이 증가하여 냉각수 부족으로 인한 전력 생산 차질이 우려되고 있다. 또한 높은 기온으로 인하여 냉각수 온도가 높아지게 되면서 전력 생산의 효율성은 떨어질 것으로 예상되고 있다.

시야를 해외로 돌리면 기후변화와 에너지 소비의 상관관계가 보다 명확해진다. 지난 2018년에 국제에너지기구(IEA)가 조사한 에너지통계연보에 따르면 석유의 비중이 32%로서 가장 크고 그다음이 27%를 차지한 석탄과 22%를 점유한 천연가스인 것으로 나타났다.

소비되는 연료의 대부분이 화석연료이며 발전용으로 사용되는 석탄의 소비가 증가했다는 것이 눈에 띈다. 이 같은 추세를 고려할 때 재생에너지 사용 비중이 아직은 부족한 상황에서 사용하는 화석연료는 지구온난화를 앞당기는 촉매제로 사용되고 있는 것으로 파악되고 있다.

재난 분야: 태풍, 대설, 지진, 풍랑, 강풍 등 자연재해 증가

행정안전부가 발간한 「재해연보」에 따르면, 지난 2004년부터 2018년까지 15년 동안 연평균 자연재난 피해액은 약 5430억 원이며, 복구액은 1조 320억 원에 달하는 것으로 나타났다.

이 중에서 최근 10년(2009년∼2018년) 사이로 기간을 좁히면 원인별 자연재난 피해액인 총 3조 6281억 원을 기준으로 호우와 태풍이 88.5%, 그리고 대설 6.6%, 지진 2.7%, 풍랑 1.2%, 강풍이 1.1%를 차지하는 것으로 드러났다.

또한 총 7조 7095억 원에 달하는 복구액은 호우·태풍 94.5%, 지진 2.5%, 대설 1.7%, 풍랑 0.5%, 강풍 0.2%인 것으로 파악됐다. 이에 따라 국회예산정책처는 기후변화의 영향을 고려한 향후 자연재난 피해액을 연간 11.5조 원으로 추정하고 있다.

향후 2020∼2060년 동안 발생 가능한 연간 자연재난 피해액은 2002년에 발생한 최대 피해액의 1.4배인 11조 4,794억 원으로 추정하였다.

기후변화와 결부되어 시설물의 노후화 및 성능 저하가 빠르게 진행되고 있다. 붕괴 또는 기능 상실시 상당한 인명·재산 피해 발생이 우려되는 댐, 하천 관리시설, 상·하수도, 절토사면 등 주요 시설물들의 노후화가 빠르게 진행되고 있다.

기후변화와 재난의 상관관계를 묘사한 저서인 『6도의 악몽(Six Degrees)』은 영국의 환경운동가이자 저널리스트인 '마크 라이너스(Mark Lynas)'가 집필했다. 라이너스는 이 저서를 통해 지구의 평균기온이 1℃에서 6℃까지 상승할 때 나타날 수 있는 기후변화 시나리오를 알기 쉬우면서도 섬뜩하게 묘사했다.

우선 지구평균 기온이 1℃ 상승하면 만년빙이 사라지고 사막화가 심화되면서 기상이변 현상이 더욱 빈번하게 나타날 것이라고 예측했다. 현재 우리가 겪고 있는 기상이변 현상과 많이 닮아 있음을 알 수 있다.

또한 지구 평균기온이 2℃ 상승하면 대가뭄과 대홍수가 닥치고, 북극의 빙하가 대부분 녹으면서 해수면이 상승하는 것으로 전망했다. 해수면이 상승하면 지구 평균기온이 3℃ 상승하면서 최악의 상황으로 가게 된다. 뉴욕시 등 해안가 주변에 형성된 도시들이 침수 사태를 겪으면서 수많은 이주민이 발생할 것이다.

이어서 4℃가 상승하게 되면 시베리아의 영구 동토층이 본격적으로 녹으면서 남극의 빙하는 하루가 다르게 사라져 버린다. 빙하가 사라진다는 것은 빙하 속에 들어있던 물질이 방출된다는 것을 의미한다. 예를 들어 영구동토층에 갇혀 있던 온실가스인 메탄이 분출되면 지구온도는 더 상승하게 된다. 빙하가 사라질수록 지구온난화가 가속될 수밖에 없는 것이다.

5℃ 상승부터는 지구가 지옥처럼 변하는 것을 목격하게 된다. 살아남은 사람들은 식량과 물을 확보하기 위해 닥치는 대로 강탈하고 살인을 저지를 것이다. 해저에 갇혀있던 메탄 하이브레이트가 분출하면서 지구의 기온은 6℃까지 올라가는데, 기온이 6℃까지 상승하게 되면 인류를 포함한 모든 동식물이 멸종하게 된다.

이 같은 비극적인 상황이 닥치기 전에 전 세계는 절박하게 힘을 합쳐야만 하는 상황이다. 물론 코로나19라는 변수가 발생하면서 인류의 생존에 위협을 주고 있는 상황임은 분명하지만, 모든 인류를 위험에 빠뜨릴 정도의 규모는 아니다. 게다가 바이러스 발생은 위생이나 날씨 등의 영향에 의해 간헐적으로 나타나는 경우가 대부분이다.

하지만 기후변화는 다르다. 전 세계 인류를 멸종시킬 수 있는 힘을 갖고 있고, 지역과 시간에 상관없이 거의 동일한 현상이 일어나게 된다. 사람이 없는 오지에 들어가 산다고 한들 시간의 차이만 있을 뿐 생명을 잃는 것은 매한가지다.

따라서 그 어떤 방법을 써서라도 석탄이나 석유 같은 화석연료가 내뿜는 온실가스를 파격적으로 감축해야만 인류가 조금이라도 더 생존할 가능성이 높아진다는 것을 과학적 통계 시스템이 보여주고 있다.

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그야말로 엎친 데 덮친 격이다. 전 세계가 코로나19 사태로 초유의 고통을 겪고 있는 가운데 산불과 폭우, 태풍 등 숨돌릴 틈도 없이 연이어 발생하고 있는 자연재해로 지구가 신음하고 있다. 국내의 경우 유래가 없는 긴 장마를 경험했고, 미 서부 지역은 산불로 인해 남한 의 5분의 1에 해당하는 면적이 잿더미로 변한 상황이다.