Greenhouse gas

Greenhouse gases are special gases in the air that trap heat, keeping Earth warm enough for life. Without them, our planet would be too cold to live on. But when there are too many of these gases, they cause the Earth to get warmer than it should be. This extra warmth is called the greenhouse effect.

The most common greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Humans have been adding more of these gases to the air since the Industrial Revolution, especially by burning fossil fuels like coal, oil, and gas. This is making the Earth warmer faster than ever before.

Too much warming can cause big problems, like melting ice, rising sea levels, and changes to weather patterns. Scientists are working hard to understand how to reduce greenhouse gas emissions and protect our planet for the future.

Properties and mechanisms

Greenhouse gases are special because they can trap heat. They catch the warmth that Earth sends out into space and send some of it back to the ground. This keeps our planet warmer.

Most of the air around us is made of nitrogen and oxygen, which do not trap heat very well. But gases like carbon dioxide, methane, and nitrous oxide, even though there is only a tiny bit of them, are very good at trapping heat. When these gases are in the air, they help keep Earth warmer by catching the heat from the ground and sending some of it back. This is called the greenhouse effect.

Contributions of specific gases to the greenhouse effect

Main article: Greenhouse effect

Atmospheric gases only absorb some wavelengths of energy but are transparent to others. The absorption patterns of water vapor (blue peaks) and carbon dioxide (pink peaks) overlap in some wavelengths.

Greenhouse gases are special because they trap heat in our atmosphere, making Earth warmer. Without them, our planet would be very cold, about −18 °C (0 °F), instead of the comfortable 15 °C (59 °F) we enjoy today. Some gases, like water vapor, play a big role in keeping Earth warm.

Other gases, such as nitrous oxide and CFCs, also help trap heat. Scientists measure how strong each gas is at causing warming using something called “global warming potential.” This helps us understand how much each gas adds to the overall warming effect.

Percent contribution to total greenhouse effect
	K&T (1997)		Schmidt (2010)
Contributor	Clear Sky	With Clouds	Clear Sky	With Clouds
Water vapor	60	41	67	50
Clouds		31		25
CO₂	26	18	24	19
Tropospheric ozone (O₃)	8
N₂O + CH₄	6
Other		9	9	7
K&T (1997) used 353 ppm CO₂ and calculated 125 W/m² total clear-sky greenhouse effect; relied on single atmospheric profile and cloud model. "With Clouds" percentages are from Schmidt's (2010) interpretation of K&T (1997). Schmidt (2010) used 1980 climatology with 339 ppm CO₂ and 155 W/m² total greenhouse effect; accounted for temporal and 3-D spatial distribution of absorbers.

List of all greenhouse gases

Greenhouse gases are special gases in the air that trap heat from the sun. This keeps Earth warm, but too much heat can make the planet too hot. Some gases trap heat much better than others. For example, methane traps a lot more heat than carbon dioxide.

We measure these gases using parts per million (ppm) or parts per billion (ppb). This shows how many gas molecules are in a million or billion air molecules. Carbon dioxide levels have been rising fast, especially since the Industrial Revolution. Scientists watch these gases to learn how they change our climate.

IPCC list of greenhouse gases with lifetime, 100-year global warming potential, concentrations in the troposphere and radiative forcings. The abbreviations TAR, AR4, AR5 and AR6 refer to the different IPCC reports over the years. The baseline is pre-industrialization (year 1750).
Species	Lifetime (years) ^: 731	100-yr GWP ^: 731	Mole Fraction [ppt – except as noted] + Radiative forcing [W m⁻²]					Concentrations over time up to year 2022
Species	Lifetime (years) ^: 731	100-yr GWP ^: 731	Baseline Year 1750	TAR Year 1998	AR4 Year 2005	AR5^: 678 Year 2011	AR6^: 4–9 Year 2019	Concentrations over time up to year 2022
CO₂ [ppm]		1	278	365 (1.46)	379 (1.66)	391 (1.82)	410 (2.16)
CH₄ [ppb]	12.4	28	700	1,745 (0.48)	1,774 (0.48)	1,801 (0.48)	1866 (0.54)
N₂O [ppb]	121	265	270	314 (0.15)	319 (0.16)	324 (0.17)	332 (0.21)
CFC-11	45	4,660	0	268 (0.07)	251 (0.063)	238 (0.062)	226 (0.066)
CFC-12	100	10,200	0	533 (0.17)	538 (0.17)	528 (0.17)	503 (0.18)
CFC-13	640	13,900	0	4 (0.001)	–	2.7 (0.0007)	3.28 (0.0009)	cfc13
CFC-113	85	6,490	0	84 (0.03)	79 (0.024)	74 (0.022)	70 (0.021)
CFC-114	190	7,710	0	15 (0.005)	–	–	16 (0.005)	cfc114
CFC-115	1,020	5,860	0	7 (0.001)	–	8.37 (0.0017)	8.67 (0.0021)	cfc115
HCFC-22	11.9	5,280	0	132 (0.03)	169 (0.033)	213 (0.0447)	247 (0.0528)
HCFC-141b	9.2	2,550	0	10 (0.001)	18 (0.0025)	21.4 (0.0034)	24.4 (0.0039)
HCFC-142b	17.2	5,020	0	11 (0.002)	15 (0.0031)	21.2 (0.0040)	22.3 (0.0043)
CH₃CCl₃	5	160	0	69 (0.004)	19 (0.0011)	6.32 (0.0004)	1.6 (0.0001)
CCl₄	26	1,730	0	102 (0.01)	93 (0.012)	85.8 (0.0146)	78 (0.0129)
HFC-23	222	12,400	0	14 (0.002)	18 (0.0033)	24 (0.0043)	32.4 (0.0062)
HFC-32	5.2	677	0	–	–	4.92 (0.0005)	20 (0.0022)
HFC-125	28.2	3,170	0	–	3.7 (0.0009)	9.58 (0.0022)	29.4 (0.0069)
HFC-134a	13.4	1,300	0	7.5 (0.001)	35 (0.0055)	62.7 (0.0100)	107.6 (0.018)
HFC-143a	47.1	4,800	0	–	–	12.0 (0.0019)	24 (0.0040)
HFC-152a	1.5	138	0	0.5 (0.0000)	3.9 (0.0004)	6.4 (0.0006)	7.1 (0.0007)
CF₄ (PFC-14)	50,000	6,630	40	80 (0.003)	74 (0.0034)	79 (0.0040)	85.5 (0.0051)
C₂F₆ (PFC-116)	10,000	11,100	40	3 (0.001)	2.9 (0.0008)	4.16 (0.0010)	4.85 (0.0013)
SF₆	3,200	23,500	0.01	4.2 (0.002)	5.6 (0.0029)	7.28 (0.0041)	9.95 (0.0056)
SO₂F₂	36	4,090	0	–	–	1.71 (0.0003)	2.5 (0.0005)
NF₃	500	16,100	0	–	–	0.9 (0.0002)	2.05 (0.0004)

Factors affecting concentrations

The amount of greenhouse gases in the air changes based on a balance. Some things add these gases, like human activities and nature. Other things take them away, like water and plants.

Some greenhouse gases stay in the air for a long time. For example, carbon dioxide can stay for many years, and some of it can last for hundreds or even thousands of years. This means that even if we stop adding these gases, we will still feel their effects for a very long time.

Monitoring

Scientists watch gases in the air that trap heat, called greenhouse gases. They use special tools to count these gases and see how they get into the air. For example, they measure carbon dioxide using infrared light and other instruments for gases like methane.

These gases are measured from space using satellites like the Orbiting Carbon Observatory and from stations on the ground. Scientists also use an index called the Annual Greenhouse Gas Index to show how these gases have changed over time. This helps us learn how our choices affect the planet's temperature.

Types of sources

Natural sources

Further information: Carbon cycle

Carbon moves naturally between the air, oceans, terrestrial ecosystems, and sediments. This movement usually balances out, so carbon levels stay stable. Carbon dioxide is taken from the air mainly through photosynthesis. It enters plants and oceans. It also dissolves in water, like in oceans and lakes, and can form carbonic acid when mixed with water.

Human-made sources

Most carbon dioxide that people add to the air comes from burning fossil fuels. Other sources include making cement, fertilizer, and changes in land use, such as deforestation.^: 687 Methane emissions come from places like farms, fossil fuel production, and waste. Rice fields are an important source of these emissions.

Most greenhouse gases come from both natural and human sources. Some synthetic gases are made only by humans and do not occur naturally. Before the industrial era, gas levels were steady because natural sources and removers balanced each other. Since then, human actions like burning fossil fuels and clearing forests have added more greenhouse gases to the air.^: 115

Reducing human-caused greenhouse gases

Main article: Climate change mitigation

Main articles: Carbon dioxide removal, Net-zero emissions, and Carbon sink

There are ways to take greenhouse gases out of the air to help protect our planet. One common way is to capture carbon dioxide and store it deep underground or in special places in the soil. Scientists are also looking at ways to remove methane, another type of greenhouse gas, from the atmosphere.

These methods are important because many plans to stop big changes in our climate depend on using these techniques to keep the Earth safe and healthy.

History of discovery

Further information: History of climate change science and Greenhouse effect § History

In the late 1800s, scientists learned that some gases in the air, like water vapor and carbon dioxide, can trap heat. These gases let sunlight in but keep some of Earth’s warmth close. This makes our planet warmer than it would be otherwise. By the early 1900s, people began to understand that these gases help keep Earth’s temperature right for life.

Later, in the late 1900s, scientists found that adding more of these gases into the air makes the whole world warmer. This warming can change many parts of nature and affect our health.

Other planets

Further information: Greenhouse effect § Bodies other than Earth

Greenhouse gases are not only found on Earth. They are also in the air around other planets like Mars, Titan, and Venus. Venus has a very strong greenhouse effect. However, this could never happen to Earth. It would need the Sun to become much brighter, and that will not happen for billions of years.