What gases contribute to the greenhouse effect and how do they contribute?

By now, you will know what the greenhouse effect is and how it contributes to causing the impacts of climate change. But do you know which greenhouse gases created by humans most contribute to global warming?

Not all have the same effect, nor do they come from the same sources, and in the same way each lasts for a different time in the atmosphere. To teach you a bit more about these gases, we’ve prepared a static infograph where you can check all this data about greenhouse gases simply, in a table.

We have excluded other variables such as the formation of water of anthropogenic origin and black carbon in snow for their lesser effect.

The effect of greenhouse gases

There are five gases of human origin that contribute most – together up to 95% of the total – to the increase in global warming. Here you will discover the source of their emission, the time they spend in the atmosphere and what percentage they contribute to the greenhouse effect.

Carbon dioxide is responsible for 53% of the level of global warming. It is the result of processes such as fuel use, deforestation and production of cement and other materials. Its permanence in the atmosphere varies, but it’s very high at all times: 80% lasts for 200 years and the other 20% can take up to 30,000 years to disappear.

Methane is the next of the greenhouse gases which has the biggest effect on global warming (15%). This is generated by activities such as livestock production, agriculture, sewage treatment, natural gas and oil distribution., coal mining, fuel use and is also given off from waste tips. It lasts an average of 12 years in the atmosphere.

Halogenated compounds such as CFCs, HCFCs, HFCs, PFCs, SF6 and NF3 are responsible for 11 % of global warming and generated as a result of the production of chemicals by diverse sectors such as refrigeration and air conditioning, electrical and electronic equipment, medicine, metallurgy, and so on. Depending on the type of compound, their duration in the atmosphere varies from a few months to tens of thousands of years.

Discover in this #infographic how each #greenhouse gas affects the atmosphere

Tropospheric ozone also has an 11% effect on global warming. This is a product of the reaction between the gases carbon monoxide (CO), nitrogen dioxide (NO₂) and VOCs (Volatile Organic Compounds), given off during the burning of fuels. These gases don’t last as long in the atmosphere as others, a matter of months at the most.

Finally, nitrous oxide also contributes around 11% to the global warming total. It comes mainly from the use of fertilizers, fuel use, chemical production and sewage treatment, and lasts longer in the atmosphere, up to 114 years.

How to avoid generating greenhouse effect gases

To avoid global warming, it is necessary to reduce greenhouse gas emissions. The best way is to commit to renewable energies, which generate clean electricity without harming the environment or polluting the air. Renewables also help preserve the oceans and forests, which are natural carbon sinks absorbing some of the carbon dioxide.

Sources: IPCC, European Commission, IDEAM, IDEAM II, IPCC II, IPCC III, World Meteorological Organization and IPCC IV.

Behind the phenomena of global warming and climate change lies the increase in greenhouse gases in our atmosphere. A greenhouse gas is any gaseous compound in the atmosphere that is capable of absorbing infrared radiation, thereby trapping and holding heat in the atmosphere. By increasing the heat in the atmosphere, greenhouse gases are responsible for the greenhouse effect, which ultimately leads to global warming. (The effects of global warming can been seen across the globe.)

Related: 10 signs that Earth's climate is off the rails

Solar radiation and the "greenhouse effect"

Global warming isn't a recent scientific concept. The basics of the phenomenon were worked out well over a century ago by Swedish physicist and chemist Svante Arrhenius, in 1896. His paper, published in the Philosophical Magazine and Journal of Science, was the first to quantify the contribution of carbon dioxide to what scientists now call the "greenhouse effect."

The greenhouse effect occurs because the sun bombards Earth with enormous amounts of radiation that strike Earth's atmosphere in the form of visible light, plus ultraviolet (UV), infrared (IR) and other types of radiation that are invisible to the human eye. UV radiation has a shorter wavelength and a higher energy level than visible light, while IR radiation has a longer wavelength and a weaker energy level. About 30% of the radiation that strikes Earth is reflected back out to space by clouds, ice and other reflective surfaces. The remaining 70% is absorbed by the oceans, the land and the atmosphere, according to NASA's Earth Observatory.

As they heat up, the oceans, land and atmosphere release heat in the form of IR thermal radiation, which passes out of the atmosphere and into space. It's this equilibrium of incoming and outgoing radiation that makes the Earth habitable, with an average temperature of about 59 degrees Fahrenheit (15 degrees Celsius), according to NASA. Without this atmospheric equilibrium, Earth would be as cold and lifeless as its moon, or as blazing hot as Venus. The moon, which has almost no atmosphere, is about minus 243 F (minus 153 C) on its dark side. Venus, on the other hand, has a very dense atmosphere that traps solar radiation; the average temperature on Venus is about 864 F (462 C).

The exchange of incoming and outgoing radiation that warms the Earth is often referred to as the greenhouse effect because an agricultural greenhouse works in much the same way. Incoming shortwave UV radiation easily passes through the glass walls of a greenhouse and is absorbed by the plants and hard surfaces inside. Weaker, longwave IR radiation, however, has difficulty passing through the glass walls and is thereby trapped inside, warming the greenhouse.

How greenhouse gases cause global warming

The gases in the atmosphere that absorb radiation are known as "greenhouse gases" (abbreviated as GHG) because they are largely responsible for the greenhouse effect. The greenhouse effect, in turn, is one of the leading causes of global warming. The most significant greenhouse gases, according to the Environmental Protection Agency (EPA), are: water vapor (H2O), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). 

"While oxygen (O2) is the second most abundant gas in our atmosphere, O2 does not absorb thermal infrared radiation," Michael Daley, an associate professor of environmental science at Lasell College in Massachusetts, told Live Science.

Global warming and the greenhouse gases that cause it occur naturally — without them, Earth's average surface temperature would be a gelid zero degrees F (minus 18 C). But the amount of greenhouse gases in the atmosphere has skyrocketed to detrimental levels in recent history. 

Related: Carbon dioxide soars to record breaking levels not seen in at least 800,000 years

During the 20,000-year period before the Industrial Revolution, atmospheric CO2 fluctuated between about 180 parts per million (ppm) during ice ages and 280 ppm during interglacial warm periods. However, since the beginning of the Industrial Revolution in the 1750s, the amount of CO2 has risen nearly 50%, according to NASA’s Global Climate Change portal. Today, CO2 levels stand at over 410 ppm.

Fluorinated gases — gases to which the element fluorine has been added — are created during industrial processes and are also considered greenhouse gases. These include hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride. Although they are present in the atmosphere in very small concentrations, they trap heat very effectively, making them high "global warming potential" (GWP) gases.

Chlorofluorocarbons (CFCs), once used as refrigerants and aerosol propellants until they were phased out by international agreement, are also greenhouse gases.

Related: Global warming vs. solar cooling: The showdown begins in 2020

There are three factors that affect the degree to which a greenhouse gas will influence global warming: Its abundance in the atmosphere, how long it stays in the atmosphere and its GWP. For example, water vapor is the most abundant greenhouse gas, but carbon dioxide has a more significant impact on global warming due to its abundance in the atmosphere plus its relatively long atmospheric lifetime of 300 to 1,000 years, according to NASA. Water vapor, on the other hand, has an atmospheric lifetime of no more than 10 days, according to a 2020 study published in the Journal of the Atmospheric Sciences.

Methane is about 21 times more efficient at absorbing radiation than CO2, giving it a higher GWP rating, even though it stays in the atmosphere for only about 12 years, according to the United Nations Framework Convention on Climate Change (UNFCCC). Although methane and other GHGs are capable of trapping more heat than CO2, scientists still consider carbon dioxide to be the dominant greenhouse gas because its warming effect outlives the others' effects by centuries.

Sources of greenhouse gases

Some greenhouse gases, such as methane, are produced through agricultural practices, in the form of livestock manure, for example. Others, like CO2, largely result from natural processes like respiration, and from the burning of fossil fuels like coal, oil and gas.

Another primary source of CO2 is deforestation. When trees are felled to produce goods or heat, they release the carbon that is normally stored for photosynthesis. This process releases up to 4.8 billion metric tons of carbon into the atmosphere every year, according to the World Resources Institute.

Forestry and other land-use practices can offset some of these greenhouse gas emissions. "Replanting helps to reduce the buildup of carbon dioxide in the atmosphere as growing trees sequester carbon dioxide through photosynthesis," Daley told Live Science. "However, forests cannot sequester all of the carbon dioxide we are emitting to the atmosphere through the burning of fossil fuels, and a reduction in fossil fuel emissions is still necessary to avoid buildup in the atmosphere."

Worldwide, the output of greenhouse gases is a source of grave concern. According to NOAA’s Climate.gov, over the past 60 years, atmospheric CO2 has increased at an annual rate that's 100 times faster than previous natural increases. The last time global atmospheric CO2 amounts were this high was 3 million years ago, when temperatures were up to 5.4 degrees F (3 degrees C) higher than during the pre-industrial era. As a result of modern-day CO2-induced global warming, 2016 was the warmest year on record, with 2019 and 2020 ranking as the next warmest, respectively. In fact, the six hottest years on record have all occurred since 2015, according to the World Meteorological Organization.

"The warming we observe affects atmospheric circulation, which impacts rainfall patterns globally," said Josef Werne, an associate professor in the Department of Geology and Planetary Science at the University of Pittsburgh. "This will lead to big environmental changes, and challenges, for people all across the globe."

Our planet's future

If current trends continue, scientists, government officials and a growing number of citizens fear that the worst effects of global warming — extreme weather, rising sea levels, plant and animal extinctions, ocean acidification, major shifts in climate and unprecedented social upheaval — will be inevitable.

In an effort to combat GHG-induced global warming, the U.S. government created a climate action plan in 2013. And in April 2016, representatives from 73 countries signed the Paris Agreement, an international pact to combat climate change by investing in a sustainable, low-carbon future, according to the UNFCCC. Although the U.S. withdrew from the Paris Agreement in 2017, it rejoined in late-January 2021. President Biden's administration has also set a target of reducing U.S. emissions by 50-52% of 2005 levels by the year 2030. (Emissions are routinely compared to those in 2005 — the year U.S. emissions of CO2 peaked at nearly 6 billion tons.)

In 2020, global carbon dioxide emissions fell 6.4% (13% in the U.S. alone) — the first time in decades the annual rate hasn’t climbed, Nature reported (opens in new tab). This was in part due to the decrease in fossil fuel combustion resulting from the switch to natural gas from coal, but largely because of the forced standstill in economic, social and transportation activities in response to the COVID-19 pandemic. Scientists expected the annual emissions decline to actually be larger than it was, but emissions rebounded as restrictions were lifted in some nations and activities recovered toward the end of 2020. 

Related: Global carbon emissions dropped an unprecedented 17% during the coronavirus lockdown — and it changes nothing

In order to limit global warming to the 2.7 degree F (1.5 degree C) target set by the Paris Agreement, the world still needs to cut its CO2 emissions by 7.6% for the next decade, according to the UN Environment Programme. 

Researchers around the world continue to work toward finding ways to lower greenhouse gas emissions and mitigate their effects. One potential solution scientists are examining is to suck some of the carbon dioxide out of the atmosphere and bury it underground indefinitely. Advocates argue that carbon capture and storage is technologically feasible, but market forces have prevented widespread adoption. 

Whether or not removing already-emitted carbon from the atmosphere is feasible, preventing future warming requires stopping the emissions of greenhouse gases. The most ambitious effort to forestall warming thus far is the 2016 Paris Agreement. This nonbinding international treaty aims to keep warming "well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius," according to the United Nations. Each signatory to the treaty agreed to set their own voluntary greenhouse gas emission limits and to make them stricter over time. Climate scientists said that the emissions limits committed under the agreement wouldn't keep warming as low as 1.5 or even 2 degrees C, but that it would be an improvement over the "business-as-usual" scenario.

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