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Hello guys! Vocês colocaram bastante conteúdo, mas faltou organização, poderiam ter numerado para direcionar melhor os visitantes. Faltou adicionar também vídeos, música, etc. Mas o trabalho ficou bom! 

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Hello guys! Vocês colocaram bastante conteúdo, mas faltou organização, poderiam ter numerado para direcionar melhor os visitantes. Faltou adicionar também vídeos, música, etc. Mas o trabalho ficou bom! 

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Maria Cristina

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Hello guys! Vocês colocaram bastante conte

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Hello guys! Vocês colocaram bastante conte

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Q: How is global warming linked to extreme weather?

A: Scientists agree that the earth’s rising temperatures are fueling longer and hotter heat waves, more frequent droughts, heavier rainfall, and more powerful hurricanes. In 2015, for example, scientists said that an ongoing drought in California—the state’s worst water shortage in 1,200 years—had been intensified by 15 percent to 20 percent by global warming. They also said the odds of similar droughts happening in the future had roughly doubled over the past century. And in 2016, the National Academies of Science, Engineering, and Medicine announced that it’s now possible to confidently attribute certain weather events, like some heat waves, directly to climate change.

The earth’s ocean temperatures are getting warmer, too—which means that tropical storms can pick up more energy. So global warming could turn, say, a category 3 storm into a more dangerous category 4 storm. In fact, scientists have found that the frequency of North Atlantic hurricanes has increased since the early 1980s, as well as the number of storms that reach categories 4 and 5. In 2005, Hurricane Katrina—the costliest hurricane in U.S. history—struck New Orleans; the second-costliest, Hurricane Sandy, hit the East Coast in 2012.

The impacts of global warming are being felt across the globe. Extreme heat waves have caused tens of thousands of deaths around the world in recent years. And in an alarming sign of events to come, Antarctica has been losing about 134 billion metric tons of ice per year since 2002. This rate could speed up if we keep burning fossil fuels at our current pace, some experts say, causing sea levels to rise several meters over the next 50 to 150 years.

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Q: What causes global warming?

A: Global warming occurs when carbon dioxide (CO2) and other air pollutants and greenhouse gasses collect in the atmosphere and absorb sunlight and solar radiation that have bounced off the earth's surface. Normally, this radiation would escape into space-but these pollutants, which last for years to centuries in the atmosphere, trap the heat and cause the planet to get hotter. That's what the greenhouse effect is.

In the United States, a burning of fossil fuels for electricity is a major source of pollution caused by heating, producing about two billion tonnes of CO2 per year. As coal-fired power plants are by far the biggest polluters. The second largest source of carbon in the country is the transportation sector, which accounts for about 1.7 billion tons of CO2 emissions per year. THE
Reducing Dangerous Climate Change Requires Deep Cuts of Emissions as well as the Use of Alternatives to Fossil Fuels EVERYWHERE. The good news is that you should start a turnaround: as CO2 emissions in the United States have declined from 2005 to 2014, thanks in part to new technologies for energy efficiency and cleaner fuel use. And scientists continue to develop new ways of modernization like power plants, generate clean electricity, and burn less gasoline we drive. The challenge is that solutions are used and widely adopted.

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Q: What is global warming?

A: Here's a simple definition of global warming. (And yes, it's really happening.) Over the past 50 years, the average global temperature has increased at the fastest rate in recorded history. And experts see the trend is accelerating: All but one of the 16 hottest years in NASA’s 134-year record have occurred since 2000.

Climate change deniers have argued that there has been a “pause” or a “slowdown” in rising global temperatures, but several recent studies, including a 2015 paper published in the journal Science, have disproved this claim. And scientists say that unless we curb global-warming emissions, average U.S. temperatures could increase by up to 10 degrees Fahrenheit over the next century.

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Prevention of water pollution.

Dealing with water pollution is something that everyone (including governments and local councils) needs to get involved with. Here are a few things you can do to help. Learning about the issue (like you are doing) is the greatest and most important step to take. Here are a few more:

You can helpNever throw rubbish away anyhow. Always look for the correct waste bin. If there is none around, please take it home and put it in your trash can. This includes places like the beach, riverside and water bodies.

Use water wisely. Do not keep the tap running when not in use. Also, you can reduce the amount of water you use in washing and bathing. If we all do this, we can significantly prevent water shortages and reduce the amount of dirty water that needs treatment.

Do not throw chemicals, oils, paints and medicines down the sink drain, or the toilet. In many cities, your local environment office can help with the disposal of medicines and chemicals. Check with your local authorities if there is a chemical disposal plan for local residents.

Buy more environmentally safe cleaning liquids for use at home and other public places. They are less dangerous to the environment.

If you use chemicals and pesticides for your gardens and farms, be mindful not to overuse pesticides and fertilizers. This will reduce runoffs of the chemical into nearby water sources. Start looking at options of

composting and using organic manure instead.

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Access to clean water is one of the world’s largest health and environmental problems. Pollution of water sources creates a chemical, biological, or physical change in water quality that causes harmful effects on the inhabitants of the water or makes the water unusable for its desired purposes¹. Water pollution can come from either point or non-point sources¹. Point sources are specifically identifiable sources and could include a pipe from a plant disposing of waste into a river¹. A non-identifiable source is a non-point source and includes water runoff from agriculture, lawns, and parking lots¹.A six mile stretch of the Willamette River was a superfund site in 2000 because the riverbed sediments showed high levels of contamination by metals and chemicals that included pesticides and herbicides². A superfund designation requires that responsible parties clean up or pay to clean up the sites that have been contaminated heavily with pollution that is hazardous to humans and the environment³. Historically, pollution in the Willamette River was from point sources such as paper mills but more recently the contamination has come from non-point sources especially where pesticides and manure are present⁴. Assessments of ground water in the Willamette basin have reveled nitrogen, pesticides, phosphorus, volatile organic compounds, and radon contamination⁵. Additionally, late in 2008, seven pesticides were found in Oregon’s groundwater that posed risks to human and environmental health⁶.

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WHAT CAN BE DONE?

Industrialized countries have worked to reduce levels of sulfur dioxide, smog, and smoke in order to improve people's health. But a result, not predicted until recently, is that the lower sulfur dioxide levels may actually make global warming worse. Just as sulfur dioxide from volcanoes can cool the planet by blocking sunlight, cutting the amount of the compound in the atmosphere lets more sunlight through, warming the Earth. This effect is exaggerated when elevated levels of other greenhouse gases in the atmosphere trap the additional heat.

Most people agree that to curb global warming, a variety of measures need to be taken. On a personal level, driving and flying less, recycling, and conservation reduces a person’s "carbon footprint"—the amount of carbon dioxide a person is responsible for putting into the atmosphere.

On a larger scale, governments are taking measures to limit emissions of carbon dioxide and other greenhouse gases. The Paris Agreement, a voluntary agreement among 118 nations ratified on November 4, 2016, is one effort being enacted on a global scale to combat climate change. As a part of the agreement, each country agreed to take measures to combat climate change, with the ultimate goal of keeping the post-industrial global temperature rise below two degrees Celcius. Another method is to put taxes on carbon emissions or higher taxes on gasoline, so that individuals and companies will have greater incentives to conserve energy and pollute less.

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OTHER GREENHOUSE GASSES

Other greenhouse gases include methane—which comes from such sources as swamps and gas emitted by livestock—and chlorofluorocarbons (CFCs), which were used in refrigerants and aerosol propellants until they were banned because of their deteriorating effect on Earth's ozone layer.
Another pollutant associated with climate change is sulfur dioxide, a component of smog. Sulfur dioxide and closely related chemicals are known primarily as a cause of acid rain. But they also reflect light when released in the atmosphere, which keeps sunlight out and causes Earth to cool. Volcanic eruptions can spew massive amounts of sulfur dioxide into the atmosphere, sometimes causing cooling that lasts for years. In fact, volcanoes used to be the main source of atmospheric sulfur dioxide; today people are.

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THE LEADING POLLUTANT

Carbon dioxide, a greenhouse gas, is the main pollutant that is warming Earth. Though living things emit carbon dioxide when they breathe, carbon dioxide is widely considered to be a pollutant when associated with cars, planes, power plants, and other human activities that involve the burning of fossil fuels such as gasoline and natural gas. In the past 150 years, such activities have pumped enough carbon dioxide into the atmosphere to raise its levels higher than they have been for hundreds of thousands of years.

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Pollution, we hear it every other day at school, college and read about it in newspapers. So what is it? Pollution occurs when pollutants contaminate the natural surroundings; which brings about changes that affect our normal lifestyles adversely. Pollutants are the key elements or components of pollution which are generally waste materials of different forms. Pollution disturbs our ecosystem and the balance in the environment. With modernization and development in our lives pollution has reached its peak; giving rise to global warming and human illness.

Pollution occurs in different forms; air, water, soil, radioactive, noise, heat/ thermal and light. Every form of pollution has two sources of occurrence; the point and the non-point sources. The point sources are easy to identify, monitor and control, whereas the non-point sources are hard to control. Let us discuss the different types of pollutions, their causes and effects on mankind and the environment as a whole.

Types & Causes of Pollution

Air Pollution is the most prominent and dangerous form of pollution. It occurs due to many reasons. Excessive burning of fuel which is a necessity of our daily lives for cooking, driving and other industrial activities; releases a huge amount of chemical substances in the air everyday; these pollute the air.

Smoke from chimneys, factories, vehicles or burning of wood basically occurs due to coal burning; this releases sulphur dioxide into the air making it toxic. The effects of air pollution are evident too. Release of sulphur dioxide and hazardous gases into the air causes global warming and acid rain; which in turn have increased temperatures, erratic rains and droughts worldwide; making it tough for the animals to survive. We breathe in every polluted particle from the air; result is increase in asthma and cancer in the lungs.

Water Pollution has taken toll of all the surviving species of the earth. Almost 60% of the species live in water bodies. It occurs due to several factors; the industrial wastes dumped into the rivers and other water bodies cause an imbalance in the water leading to its severe contamination and death of aquatic species. If you suspect that nearby water sources have been contaminated by a corporation then it might be a good idea to hire an expert to see your options.

Also spraying insecticides, pesticides like DDT on plants pollutes the ground water system and oil spills in the oceans have caused irreparable damage to the water bodies. Eutrophication is another big source; it occurs due to daily activities like washing clothes, utensils near lakes, ponds or rivers; this forces detergents to go into water which blocks sunlight from penetrating, thus reducing oxygen and making it inhabitable.

Water pollution not only harms the aquatic beings but it also contaminates the entire food chain by severely affecting humans dependent on these. Water-borne diseases like cholera, diarrhoea have also increased in all places.

Soil pollution occurs due to incorporation of unwanted chemicals in the soil due to human activities. Use of insecticides and pesticides absorbs the nitrogen compounds from the soil making it unfit for plants to derive nutrition from. Release of industrial waste, mining and deforestation also exploits the soil. Since plants can't grow properly, they can't hold the soil and this leads to soil erosion.

Noise pollution is caused when noise which is an unpleasant sound affects our ears and leads to psychological problems like stress, hypertension, hearing impairment, etc. It is caused by machines in industries, loud music, etc.

Radioactive pollution is highly dangerous when it occurs. It can occur due to nuclear plant malfunctions, improper nuclear waste disposal, accidents, etc. It causes cancer, infertility, blindness, defects at the time of birth; can sterilise soil and affect air and water.

Thermal/heat pollution is due to the excess heat in the environment creating unwanted changes over long time periods; due to huge number of industrial plants, deforestation and air pollution. It increases the earth's temperature, causing drastic climatic changes and extinction of wildlife.

Light pollution occurs due to prominent excess illumination of an area. It is largely visible in big cities, on advertising boards and billboards, in sports or entertainment events at the night. In residential areas the lives of the inhabitants is greatly affected by this. It also affects the astronomical observations and activities by making the stars almost invisible.

Effects of Pollution

1. Environment Degradation : Environment is the first casualty for increase in pollution weather in air or water. The increase in the amount of CO2 in the atmosphere leads to smog which can restrict sunlight from reaching the earth. Thus, preventing plants in the process of photosynthesis. Gases like Sulfur dioxide and nitrogen oxide can cause acid rain. Water pollution in terms of Oil spill may lead to death of several wildlife species.

2. Human Health : The decrease in quality of air leads to several respiratory problems including asthma or lung cancer. Chest pain, congestion, throat inflammation, cardiovascular disease, respiratory disease are some of diseases that can be causes by air pollution. Water pollution occurs due to contamination of water and may pose skin related problems including skin irritations and rashes. Similarly, Noise pollution leads to hearing loss, stress and sleep disturbance.

3. Global Warming : The emission of greenhouse gases particularly CO2 is leading to global warming. Every other day new industries are being set up, new vehicles come on roads and trees are cut to make way for new homes. All of them, in direct or indirect way lead to increase in CO2 in the environment. The increase in CO2 leads to melting of polar ice caps which increases the sea level and pose danger for the people living near coastal areas.

4. Ozone Layer Depletion: Ozone layer is the thin shield high up in the sky that stops ultra violet rays from reaching the earth. As a result of human activities, chemicals, such as chlorofluorocarbons (CFCs), were released int to the atmosphere which contributed to the depletion of ozone layer.

5. Infertile Land : Due to constant use of insecticides and pesticides, the soil may become infertile. Plants may not be able to grow properly. Various forms of chemicals produced from industrial waste is released into the flowing water which also affects the quality of soil.

Pollution not only affect humans by destroying their respiratory, cardiovascular and neurological systems; it also affects the nature, plants, fruits, vegetables, rivers, ponds, forests, animals, etc, on which they are highly dependent for survival. It is crucial to control pollution as the nature, wildlife and human life are precious gifts to the mankind.

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Pollution: Causes and Effects - Conserve Energy Future

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Pollution, we hear it every other day at school, college and read about it in newspapers. So what is it? Pollution occurs when pollutants contaminate the natural surroundings; which brings about changes that affect our normal lifestyles adversely.

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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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Para descomplicar os conceitos técnicos do trabalho do WRI Brasil, lançamos a série de vídeos WRI Explica. Uma forma simples de apresentar os conceitos e compartilhar o conhecimento dos assuntos abordados em nossas publicações. Divirta-se.

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Apoena

Aquecimento global provoca derretimento da geleira Perito Moreto na Patagônia

Mudança climática é o nome que se dá ao conjunto de alterações nas condições do clima da Terra pelo acúmulo de seis tipos de gases - como o dióxido de carbono (CO2) e o metano (CH4) - na atmosfera, emitidos em quantidade excessiva há pelo menos 150 anos, desde a Revolução Industrial, através da queima de combustíveis fósseis, como o petróleo e o carvão, e do uso inadequado da terra com a conversão das florestas e da vegetação natural em pastagens, plantações, áreas urbanas ou degradadas.

Estes gases - também chamados gases de efeito estufa - formam uma espécie de cobertor na atmosfera, que impede que os raios solares que incidem sobre a Terra sejam emitidos de volta ao espaço, acumulando calor e provocando o aumento da temperatura na sua superfície, assim como ocorre numa estufa de plantas. São gases que sempre estiveram presentes na composição da atmosfera, mas estima-se que há atualmente acúmulo de cerca de 30% a mais do que havia antes da Revolução Industrial, e a sua emissão continua crescendo, o que altera as condições climáticas naturais anteriores.

Estima-se, também, que a temperatura da Terra aumentou 0,7 grau centígrado no último século e que os últimos dez anos foram os mais quentes da história. Parece pouco, mas a provável intensificação desse processo deverá provocar o degelo nos pólos e em outras regiões geladas do planeta, com o conseqüente aumento do nível dos oceanos. Assim, ficarão afetados os ecossistemas marinhos,as correntes e as ilhas oceânicas, as praias, os mangues e as áreas urbanas mais baixas das cidades litorâneas.

O efeito estufa já vem afetando o regime de chuvas em várias partes do mundo, provocando secas e enchentes mais intensas, com sérias conseqüências para a agricultura. O fenômeno El Nino - provocado pelo aquecimento das águas do Oceano Pacífico nas proximidades da costa peruana - está associado ao efeito estufa, que aumenta a sua freqüência e intensidade, e tem afetado o clima sul-americano - e brasileiro - além de outras regiões. Também se atribui ao efeito estufa o aumento em número e intensidade de ocorrências catastróficas como ciclones e furacões.

Segundo previsões da maior parte dos cientistas, o mundo todo sofrerá com o impacto da mudança climática já no decorrer deste século. Além de ameaçar a sobrevivência de inúmeras espécies, que não terão tempo de se adaptar a elas, sofrerão, em particular, as populações humanas cuja sobrevivência dependa da pesca ou da agricultura. Embora os países desenvolvido sejam os principais responsáveis históricos pelo acúmulo de gases estufa na atmosfera, estima-se que os países pobres serão mais duramente afetados pela mudança climática. O caso mais grave é dos países insulares da Oceania que, com o aumento do nível do oceano - e em vista da sua baixa altitude - correm o risco de submersão.
O Protocolo de Quioto e o MDL
Diante do consenso da comunidade cientifica, reunida no IPCC (Painel Inter-governamental sobre Mudanças Climáticas - em português), quanto ao aumento da temperatura na Terra, a ONU aprovou a Convenção Quadro sobre as Mudanças Climáticas Globais, subscrita pelos chefes de estado reunidos no Rio de Janeiro durante a Rio-92. Sete anos depois, em 1997, como a recomendação da Convenção para que os países desenvolvidos reduzissem as suas emissões não estava sendo cumprida, foi aprovado, dentro do seu marco jurídico, um novo instrumento - o Protocolo de Quioto - para estabelecer prazos e metas obrigatórias. Estas metas - redução média de 5,2% em relação ao nível de emissões dos paises industrializados em 1990 - são insuficientes para reverter a gravidade da situação do clima, mas seriam um começo.

O Protocolo de Quioto começou a vigorar em 2005, quando 139 paises o ratificaram demonstrando intenção da comunidade global de combater o aquecimento global. Hoje, 169 países mais a União Européia estão dentro do tratado. Infelizmente, alguns países que poluem muito, como os Estados Unidos (responsável por 25% das emissões), ainda não ratificam o Protocolo.

Durante o primeiro período de vigência, previsto para 2008-2012, apenas os países desenvolvidos - emissores históricos - terão metas obrigatórias de redução de emissões. Alguns países em desenvolvimento, como a China, o Brasil e a Índia, incluem-se entre os maiores emissores atuais, mas a sua participação nos esforços pró-reduções neste período estará restrita ao Mecanismo de Desenvolvimento Limpo (MDL), que prevê que os países desenvolvidos poderão financiar projetos em países em desenvolvimento para compensar reduções de emissões não realizadas internamente.

Vários tipos de projetos podem ser executados para reduzir emissões de gases estufa. Por exemplo, se a frota de ônibus de uma cidade, movida a diesel ou gasolina, for substituída por ônibus elétricos, retirando-se os veículos anteriores de circulação, estará havendo redução de emissões, pois a produção e o uso da energia elétrica implica em menor liberação de gases estufa que a queima daqueles combustíveis. O governo brasileiro cancelou projetos para fins de detalhamento com vistas ao MDL, que visam a redução na emissão de metano em lixões (em Duque de Caxias, Rio de Janeiro e em Salvador, Bahia).

Outros projetos, que também são admitidos no MDL, podem objetivar a retirada (seqüestro) de parte do carbono acumulado na atmosfera, em vez da redução de emissões. Seria o caso do reflorestamento: enquanto a vegetação estiver crescendo em determinadas áreas que anteriormente estivessem desmatadas, carbono estará sendo retirado da atmosfera para incorporar-se à massa vegetal. Assim, o benefício climático do seqüestro do carbono será temporário, enquanto que a redução de reduções promove um benefício permanente.

Além do MDL, o Protocolo de Quioto prevê outros dois mecanismos de compensação que, no entanto, só se prestarão a negociações entre os paises desenvolvidos que têm metas de redução de emissões para cumprir. As transações econômicas entre países decorrentes da aplicação destes mecanismos conformarão o mercado do carbono. Mas, além dos mecanismos oficialmente previstos, este mercado também será constituído por transações extra Protocolo, entre países ou empresas que tenham interesse em reduzir seus passivos em emissões independentemente dos acordos multilaterais.

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Apoena Aquecimento global provoca derretimento da geleira Perito Moreto na Patagônia Mudança climática é o nome que se dá ao conjunto de alterações nas condições do clima da Terra pelo acúmulo de seis tipos de gases - como o dióxido de carbono (CO2) e o metano (CH4) - na atmosfera, emitidos em quantidade excessiva há pelo menos 150 anos, desde a Revolução Industrial, através da queima de combustíveis fósseis, como o petróleo e o carvão, e do uso inadequado da terra com a conversão das florestas e da vegetação natural em pastagens, plantações, áreas urbanas ou degradadas.

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What can you do?All of us can actively limit the emission of greenhouse gases. It means we have a chance to slow down the temperature rise on the planet. If we become aware of our use of energy in our daily lives and choose to support companies that are committed to climate change, we can help build a better future for our planet.

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What can you do?All of us can actively limit the emission of greenhouse gases. It means we have a chance to slow down the temperature rise on the planet. If we become aware of our use of energy in our daily lives and choose to support companies that are committed to climate change, we can help build a better future for our planet.

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What are the main causes of Climate Change?There are natural causes that contribute to climate change, but industrial processes are behind the recent rapid acceleration of global warming. The needs of a growing population have led to deforestation, the burning of fossil fuels and intensive agriculture. All these activities release greenhouse gases into our atmosphere - such as carbon dioxide, nitrous oxide and methane. Greenhouse gases trap the heat of the sun on the planet, preventing it from being reflected back into space. This causes the Earth's atmosphere to warm up in what is known as the greenhouse effect. In just 200 years, the concentration of carbon dioxide in our atmosphere has increased by 30%

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What are the main causes of Climate Change?There are natural causes that contribute to climate change, but industrial processes are behind the recent rapid acceleration of global warming. The needs of a growing population have led to deforestation, the burning of fossil fuels and intensive agriculture. All these activities release greenhouse gases into our atmosphere - such as carbon dioxide, nitrous oxide and methane. Greenhouse gases trap the heat of the sun on the planet, preventing it from being reflected back into space. This causes the Earth's atmosphere to warm up in what is known as the greenhouse effect. In just 200 years, the concentration of carbon dioxide in our atmosphere has increased by 30%

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Simply put, climate change, also known as global warming, is due to the global average temperature rise. Increasing emissions of greenhouse gases into the atmosphere (CO2 in particular) are arresting heat in the Earth's atmosphere. This impacts global climate systems, causing, from unexpected rain to extreme heat waves. The Earth has gone through periods of warming and cooling - and associated climate change - many times. What the scientists are most concerned about is that the warming process is happening much faster than before, and that the rapid warming is caused by the increased levels of man-made emissions.

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Simply put, climate change, also known as global warming, is due to the global average temperature rise. Increasing emissions of greenhouse gases into the atmosphere (CO2 in particular) are arresting heat in the Earth's atmosphere. This impacts global climate systems, causing, from unexpected rain to extreme heat waves. The Earth has gone through periods of warming and cooling - and associated climate change - many times. What the scientists are most concerned about is that the warming process is happening much faster than before, and that the rapid warming is caused by the increased levels of man-made emissions.

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WHAT ARE CLIMATE CHANGE?WHAT CAN WE DO ABOUT?

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WHAT ARE CLIMATE CHANGE?WHAT CAN WE DO ABOUT?