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Get to know what’s good and bad using these cards.

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Earth Science, Climatology

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Photograph by Emory Kristof/ National Geographic

Global warming is the long-term warming of the planet's overall temperature. Though this warming trend has been going on for a long time, its pace has significantly increased in the last hundred years due to the burning of fossil fuels. As the human population has increased, so has the volume of fossil fuels burned. Fossil fuels include coal, oil, and natural gas, and burning them causes what is known as the "greenhouse effect" in Earth's atmosphere.

The greenhouse effect is when the sun's rays penetrate the atmosphere, but when that heat is reflected off the surface cannot escape back into space. Gases produced by the burning of fossil fuels prevent the heat from leaving the atmosphere. These greenhouse gasses are carbon dioxide, chlorofluorocarbons, water vapor, methane, and nitrous oxide. The excess heat in the atmosphere has caused the average global temperature to rise overtime, otherwise known as global warming.

Global warming has presented another issue called climate change. Sometimes these phrases are used interchangeably, however, they are different. Climate change refers to changes in weather patterns and growing seasons around the world. It also refers to sea level rise caused by the expansion of warmer seas and melting ice sheets and glaciers. Global warming causes climate change, which poses a serious threat to life on Earth in the forms of widespread flooding and extreme weather. Scientists continue to study global warming and its impact on Earth.

Director

Tyson Brown, National Geographic Society

Author

National Geographic Society

Production Managers

Gina Borgia, National Geographic Society

Jeanna Sullivan, National Geographic Society

Program Specialists

Sarah Appleton, National Geographic Society, National Geographic Society

Margot Willis, National Geographic Society

Last Updated

October 19, 2023

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Earth is warming up, and humans are at least partially to blame. The causes, effects, and complexities of global warming are important to understand so that we can fight for the health of our planet.

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Unit 2 Lesson 8 Greenhouse Gases Powerpoint

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carbon footprint - the number of greenhouse gases a person emits directly or indirectly

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carbon footprint - the number of greenhouse gases a person emits directly or indirectly

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A carbon footprint is the total amount of greenhouse gases (including carbon dioxide and methane) that are generated by our actions. The average carbon footprint for a person in the United States is 16 tons, one of the highest rates in the world. Globally, the average carbon footprint is closer to 4 tons.

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Causes and Effects of Climate Change  National Geographic (1)

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What major human activity contributes to an increase in carbon dioxide?

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What major human activity contributes to an increase in carbon dioxide?

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There are both natural and human sources of carbon dioxide emissions. Natural sources include decomposition, ocean release and respiration. Human sources come from activities like cement production, deforestation as well as the burning of fossil fuels like coal, oil and natural gas.

Due to human activities, the atmospheric concentration of carbon dioxide has been rising extensively since the Industrial Revolution and has now reached dangerous levels not seen in the last 3 million years.1 2 3 Human sources of carbon dioxide emissions are much smaller than natural emissions but they have upset the natural balance that existed for many thousands of years before the influence of humans.

This is because natural sinks remove around the same quantity of carbon dioxide from the atmosphere than are produced by natural sources.4 This had kept carbon dioxide levels balanced and in a safe range. But human sources of emissions have upset the natural balance by adding extra carbon dioxide to the atmosphere without removing any

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Main sources of carbon dioxide emissions

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There are both natural and human sources of carbon dioxide emissions. Natural sources include decomposition, ocean release and respiration. Human sources come from activities like cement production, deforestation as well as the burning of fossil fuels like coal, oil and natural gas.

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Carbon dioxide (CO ₂) is a chemical compound. It is a gas at room temperature. It is made of one carbon and two oxygen atoms. People and animals release carbon dioxide when they breathe out. Also, every time something organic is burnt (or a fire is made), it makes carbon dioxide. Plants use carbon dioxide to make food. This process is called photosynthesis. The properties of carbon dioxide were studied by the Scottish scientist Joseph Black in the 1750s.

Carbon dioxide is a greenhouse gas. Greenhouse gases trap heat energy. Greenhouse gases change the climate and weather on our planet, Earth. This is called climate change. Most scientists think that greenhouse gases are causing global warming, the rise of Earth surface temperature.

Biological role

Carbon dioxide is an end product in organisms that obtain energy from breaking down sugars, fats and amino acids with oxygen as part of their metabolism. This is a process known as cellular respiration. This includes all plants, animals, many fungi and some bacteria. In higher animals, the carbon dioxide travels in the blood from the body's tissues to the lungs where it is breathed out. Plants take in carbon dioxide from the atmosphere to use in photosynthesis.

Dry ice (Do not eat)

Dry ice, or solid carbon dioxide, is the solid state of CO ₂ gas below -109.3 °F (-78.5 °C). Dry ice does not occur naturally on earth but is man made. It is colorless. We can use dry ice for making drinks fizzy, killing gophers, and freezing warts. The vapor of dry ice causes suffocation and eventually, death. Caution and professional assistance is recommended whenever dry ice is in use.

At usual pressure it will not melt from a solid to a liquid but instead changes directly from a solid to a gas. This is called sublimation. It will change directly from a solid to a gas at any temperature higher than extremely cold temperatures. Dry ice sublimates at normal air temperature. Dry ice exposed to normal air gives off carbon dioxide gas that has no odor and no color. Carbon dioxide can be liquified at pressure above 5.1 atmospheres.

Carbon dioxide gas that comes off of dry ice is so cold that when it mixes with air it cools the water vapour in the air to fog, which looks like a thick white smoke. It is often used in the theater to create the appearance of fog or smoke.

Isolation and production

Chemists get carbon dioxide from cooling air. They call this air distillation. But this method is inefficient. Chemists can also use several different chemical reactions to separate carbon dioxide. Carbon dioxide is made in the reactions between most acids and most metal carbonates. For example, the reaction between hydrochloric acid and calcium carbonate (limestone or chalk) makes carbon dioxide:

The carbonic acid (H ₂CO ₃) then decomposes to water and CO ₂. Such reactions cause foaming or bubbling, or both. In industry, such reactions are used many times to neutralize waste acid streams.

Quicklime (CaO), a chemical that has widespread use, can be made heating limestone to about 850 °C. This reaction also makes CO ₂:

Carbon dioxide is also made in the combustion of all carbon-containing fuels, such as methane ( natural gas), petroleum distillates ( gasoline, diesel, kerosene, propane), coal or wood. In most cases, water is also released. As an example the chemical reaction between methane and oxygen is:

Carbon dioxide is made in steel mills. Iron is reduced from its oxides with coke in a blast furnace, producing pig iron and carbon dioxide:

Yeast metabolizes sugar to produce carbon dioxide and ethanol, also known as alcohol, in the production of wines, beers and other spirits, but also in the production of bioethanol:

All aerobic organisms produce when they oxidize carbohydrates, fatty acids, and proteins in the mitochondria of cells. The large number of reactions involved are exceedingly complex and not described easily. (They include cellular respiration, anaerobic respiration and photosynthesis). Photoautotrophs (i.e. plants, cyanobacteria) use another reaction: Plants absorb from the air, and, together with water, react it to form carbohydrates:

Carbon dioxide is soluble in water, in which it spontaneously interconverts between CO ₂ and (carbonic acid). The relative concentrations of , and the deprotonated forms ( bicarbonate) and ( carbonate) depend on the acidity ( pH). In neutral or slightly alkaline water (pH > 6.5), the bicarbonate form predominates (>50%) becoming the most prevalent (>95%) at the pH of seawater, while in very alkaline water (pH > 10.4) the predominant (>50%) form is carbonate. The bicarbonate and carbonate forms are very soluble. So, air-equilibrated ocean water (mildly alkaline with typical pH = 8.2 - 8.5) contains about 120 mg of bicarbonate per liter.

Industrial production

Industrial carbon dioxide is produced mainly from six processes:

Chemical reaction

Carbon dioxide can be created with a simple chemical reaction:

carbon + oxygen → carbon dioxide

Images for kids

CO2 in Earth's atmosphere if half of global-warming emissions are not absorbed.( NASA computer simulation).

Overview of photosynthesis and respiration. Carbon dioxide (at right), together with water, form oxygen and organic compounds (at left) by photosynthesis, which can be respired to water and (CO2).

Rising levels of CO2 threatened the Apollo 13 astronauts who had to adapt cartridges from the command module to supply the carbon dioxide scrubber in the lunar module, which they used as a lifeboat.

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Carbon dioxide (CO 2) is a chemical compound. It is a gas at room temperature. It is made of one carbon and two oxygen atoms. People and animals release carbon dioxide when they breathe out. Also, every time something organic is burnt (or a fire is made), it makes carbon dioxide.

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The term carbon footprint is how much carbon goes into the air because of something done by people (not by nature). Doing something that burns fuel will make carbon dioxide gas in the smoke. Carbon dioxide has carbon in it. Just as walking on the sand leaves a footprint, burning fuel leaves carbon dioxide in the air, which is called a carbon footprint. Total carbon footprint/emission quantification would include energy emissions from human activities - that is, from heat, light, power and refrigeration and all transport related emissions from cars, freight and distribution.

Where it comes from

Oil, gas, and coal are called "fossil fuels" because they come from fossils of ancient plants and animals. Those plants and animals had carbon in them. So when we burn oil, gas, and coal, the carbon becomes carbon dioxide and goes into the air as smoke. This makes pollution. It also makes the greenhouse effect, which means that the carbon dioxide makes the earth warmer, like a greenhouse. A carbon footprint is the carbon dioxide that is put into the air because of a person, a group of people, an event or a product.

The words "carbon footprint" are often seen in the news. They are used with the word sustainability, which means that we can keep doing something without making something bad happen. That is, if there is too much of a carbon footprint, then there is no sustainability. People and businesses are often asked to think about how much carbon they are putting into the air, and how this changes the environment and maybe causes global warming. This is often said about traveling by airplane or by car, because burning fuel makes carbon dioxide gas.

The most common way to reduce the carbon footprint of humans is to Reduce, Reuse, Recycle, Refuse. Another easy option is to drive less. By walking or biking to the destination rather than driving, not only is a person going to save money on gas, but they will be burning less fuel and releasing fewer emissions into the atmosphere. However, if walking is not an option, one can look into carpooling use public transportation options in their area. Yet another option for reducing the carbon footprint of humans is to use less air conditioning and heating in the home. By adding insulation to the walls and attic of one's home, and installing weather stripping or caulking around doors and windows one can lower their heating costs more than 25 percent. Choice of diet is a major influence on a person's carbon footprint. Animal sources of protein (especially red meat), rice (typically produced in high methane-emitting paddies), foods transported long distance and/or via fuel-inefficient transport (e.g., highly perishable produce flown long distance) and heavily processed and packaged foods are among the major contributors to a high carbon diet.

Images for kids

In Spanish: Huella de carbono para niños

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There is no one-size-fits-all approach to stopping or slowing global warming, and each individual, business, municipal, state, tribal, and federal entity must weigh their options in light of their own unique set of circumstances. Experts say it is likely many strategies working together will be needed. Generally speaking, here are some examples of mitigation strategies we can use to slow or stop the human-caused global warming ( learn more):

Where possible, we can switch to renewable sources of energy (such as solar and wind energy) to power our homes and buildings, thus emitting far less heat-trapping gases into the atmosphere.

Where feasible, we can drive electric vehicles instead of those that burn fossil fuels; or we can use mass transit instead of driving our own cars.

Where affordable, we can conserve energy by better insulating our homes and buildings, and by replacing old, failing appliances with more energy-efficient models.

Where practicable, we can counterbalance our annual carbon dioxide emissions by investing in commercial services that draw down an equal amount of carbon out of the atmosphere, such as through planting trees or carbon capture and storage techniques.

Where practical, we can support more local businesses that use and promote sustainable, climate-smart practices such as those listed above.

We can consider placing an upper limit on the amount of carbon dioxide we will allow ourselves to emit into the atmosphere within a given timeframe.

Note that NOAA doesn't advocate for or against particular climate policies. Instead, NOAA's role is to provide data and scientific information about climate, including how it has changed and is likely to change in the future depending on different climate policies or actions society may or may not take. More guidance on courses of action can be found in the National Academy of Sciences' 2010 report, titled Informing an Effective Response to Climate Change. Also learn more here, here, and here.

Stabilizing global temperature near its current level requires eliminating all emissions of heat-trapping gases or, equivalently, achieving a carbon-neutral society in which people remove as much carbon from the atmosphere as they emit. Achieving this goal will require substantial societal changes in energy technologies and infrastructure that go beyond the collective actions of individuals and households to reduce emissions.

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What can we do to slow or stop global warming?

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There is great potential for the collective actions of many individuals worldwide to reduce global warming by making changes in their daily and annual activities that produce heat-trapping gases and aerosols.