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 absorb the warmth that Earth sends out into space and send some of it back to the ground. This keeps our planet warmer than it would be otherwise.

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 that radiates 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

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, but humans don’t change how much water vapor is in the air directly. However, when Earth gets warmer, it can hold more water vapor, which makes the warming even stronger.

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,” which helps us understand how much each gas adds to the overall warming effect.

List of all greenhouse gases

Greenhouse gases are special types of gases in the air that trap heat from the sun. This trapping of heat keeps Earth warm, but too much of it can cause the planet to get too hot. Some gases trap heat much better than others. For example, methane traps about 84 times more heat than carbon dioxide over 20 years.

We measure how much of these gases are in the air using parts per million (ppm) or parts per billion (ppb). This tells us how many gas molecules are in a million or billion air molecules. Carbon dioxide levels have been rising fast, especially since humans started the Industrial Revolution. Scientists keep track of these gases to understand how they affect 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
			Baseline Year 1750	TAR Year 1998	AR4 Year 2005	AR5: 678  Year 2011	AR6: 4–9  Year 2019
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		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 depends on a balance between sources, like human activities and natural systems that release these gases, and sinks, which are places that absorb them such as water bodies and plants.

Some greenhouse gases stay in the air for a long time. For example, carbon dioxide can stay for many years, with some of it lasting for hundreds to thousands of years. This means that even if we stop adding these gases to the air, their effects can continue for a very long time.

Monitoring

Scientists keep track of gases in the air that trap heat, called greenhouse gases, by measuring how much of them are in the atmosphere. They use special tools to count these gases and also look at how they are released 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 a special index called the Annual Greenhouse Gas Index to show how much these gases have changed over time compared to levels before factories and cars became common. This helps us understand how our choices affect the planet's temperature.

Types of sources

Natural sources

Further information: Carbon cycle

The natural movement of carbon between the air, oceans, terrestrial ecosystems, and sediments is mostly balanced, so carbon levels would stay stable without human help. Carbon dioxide is taken from the air mainly through photosynthesis and enters plants and oceans. It also dissolves in water, such as in oceans and lakes, and can form carbonic acid when mixed with water.

Human-made sources

Most carbon dioxide that humans add to the air comes from burning fossil fuels. Other sources include making cement, fertilizer, and changes in how we use land, such as deforestation.^: 687  Methane emissions come from places like agriculture, fossil fuel production, and waste. Rice fields are an important source of these emissions, creating about 22% of agricultural methane and 11% of nitrous oxide emissions.

If we keep adding greenhouse gases at the same rate, temperatures could rise above 2.0 °C (3.6 °F) between 2040 and 2070, which the United Nations' Intergovernmental Panel on Climate Change says is dangerous.

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 found that some gases in the air, like water vapor and carbon dioxide, can trap heat. These gases let sunlight in but keep some of the Earth’s warmth close, making our planet warmer than it would be otherwise. By the early 1900s, people began to understand that these special gases play a big role in keeping Earth’s temperature just right for life.

Later, in the late 1900s, scientists agreed that when we put more of these heat-trapping gases into the air, it makes the whole world warmer. This warming affects many parts of nature and our health.

Other planets

Further information: Greenhouse effect § Bodies other than Earth

Greenhouse gases are not just found on Earth. They are also present in the atmospheres of other planets like Mars, Titan, and especially in the thick atmosphere of Venus. Venus experiences a very strong greenhouse effect, but this is not something that could happen to Earth because it would require the Sun to become much brighter, which will not happen for billions of years.