Product Code Database
Greenhouse gases ( GHGs) are the gases in the atmosphere that raise the surface temperature of such as the Earth. Unlike other gases, greenhouse gases absorb the radiations that a planet emits, resulting in the greenhouse effect. The Earth is warmed by sunlight, causing its surface to radiant energy, which is then mostly absorbed by greenhouse gases. Without greenhouse gases in the atmosphere, the average temperature of Earth's surface would be about , rather than the present average of .Le Treut, H., R. Somerville, U. Cubasch, Y. Ding, C. Mauritzen, A. Mokssit, T. Peterson and M. Prather, 2007: " Chapter 1: Historical Overview of Climate Change". In: " Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change". Solomon,. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
The five most abundant greenhouse gases in Earth's atmosphere, listed in decreasing order of average global mole fraction, are: water vapor, carbon dioxide, methane, nitrous oxide, ozone. Other greenhouse gases of concern include chlorofluorocarbons (CFCs and HCFCs), hydrofluorocarbons (HFCs), perfluorocarbons, , and . Water vapor causes about half of the greenhouse effect, acting in response to other gases as a climate change feedback.
Human activities since the beginning of the Industrial Revolution (around 1750) have increased carbon dioxide by over 50%, and methane levels by 150%. Carbon dioxide emissions are causing about three-quarters of global warming, while methane emissions cause most of the rest. The vast majority of carbon dioxide emissions by humans come from the burning of , with remaining contributions from agriculture and Heavy industry.Canadell, J.G., P.M.S. Monteiro, M.H. Costa, L. Cotrim da Cunha, P.M. Cox, A.V. Eliseev, S. Henson, M. Ishii, S. Jaccard, C. Koven, A. Lohila, P.K. Patra, S. Piao, J. Rogelj, S. Syampungani, S. Zaehle, and K. Zickfeld, 2021: Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change Masson-Delmotte,. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 673–816, doi:10.1017/9781009157896.007. Methane emissions originate from agriculture, fossil fuel production, waste, and other sources. The carbon cycle takes thousands of years to fully absorb from the atmosphere, while methane lasts in the atmosphere for an average of only 12 years.
carbon cycle happen between the atmosphere, terrestrial ecosystems, the ocean, and . These flows have been fairly balanced over the past one million years, although greenhouse gas levels have varied widely in Paleoclimatology. Carbon dioxide levels are now higher than they have been for three million years. If current emission rates continue then global warming will surpass sometime between 2040 and 2070. This is a level which the Intergovernmental Panel on Climate Change (IPCC) says is "dangerous".
99% of the Earth's dry atmosphere (excluding water vapor) is made up of nitrogen () (78%) and oxygen () (21%). Because their contain two atoms of the same element, they have no asymmetry in the distribution of their electrical charges, and so are almost totally unaffected by infrared thermal radiation, with only an extremely minor effect from collision-induced absorption. A further 0.9% of the atmosphere is made up by argon (Ar), which is monatomic, and so completely transparent to thermal radiation. On the other hand, carbon dioxide (0.04%), methane, nitrous oxide and even less abundant account for less than 0.1% of Earth's atmosphere, but because their molecules contain atoms of different elements, there is an asymmetry in electric charge distribution which allows molecular vibrations to interact with electromagnetic radiation. This makes them infrared active, and so their presence causes greenhouse effect.
Within the lower atmosphere, greenhouse gases exchange thermal radiation with the surface and limit radiative heat flow away from it, which reduces the overall rate of upward radiative heat transfer. (2025). 9780127329512, Academic Press. ISBN 9780127329512 The increased concentration of greenhouse gases is also cooling the upper atmosphere, as it is much thinner than the lower layers, and any heat re-emitted from greenhouse gases is more likely to travel further to space than to interact with the fewer gas molecules in the upper layers. The upper atmosphere is also shrinking as the result.
This table shows the most important contributions to the overall greenhouse effect, without which the average temperature of Earth's surface would be about , instead of around . This table also specifies tropospheric ozone, because this gas has a cooling effect in the stratosphere, but a warming influence comparable to nitrous oxide and CFCs in the troposphere.
| + Percent contribution to total greenhouse effect ! !! colspan="2" | !! colspan="2" >Schmidt (2010), D20106. Web page |
| 50 | |
| 25 | |
| 19 | |
| 7 | |
The concentration of a greenhouse gas is typically measured in parts per million (ppm) or parts per billion (ppb) by volume. A concentration of 420 ppm means that 420 out of every million air molecules is a molecule. The first 30 ppm increase in concentrations took place in about 200 years, from the start of the Industrial Revolution to 1958; however the next 90 ppm increase took place within 56 years, from 1958 to 2014. Similarly, the average annual increase in the 1960s was only 37% of what it was in 2000 through 2007. ; see also
Many observations are available online in a variety of Atmospheric Chemistry Observational Databases. The table below shows the most influential long-lived, well-mixed greenhouse gases, along with their tropospheric concentrations and direct radiative forcings, as identified by the Intergovernmental Panel on Climate Change (IPCC). Abundances of these are regularly measured by atmospheric scientists from samples collected throughout the world. It excludes water vapor because changes in its concentrations are calculated as a climate change feedback indirectly caused by changes in other greenhouse gases, as well as ozone, whose concentrations are only modified indirectly by various refrigerants that cause ozone depletion. Some short-lived gases (e.g. carbon monoxide, NOx) and (e.g. mineral dust or black carbon) are also excluded because of limited role and strong variation, along with minor refrigerants and other Halogenation gases, which have been mass-produced in smaller quantities than those in the table. and Annex III of the 2021 IPCC WG1 Report
| +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). ! rowspan="2" | Species ! rowspan="2" | Lifetime (years) ! rowspan="2" | 100-yr GWP ! colspan="5" | Mole Fraction ppt + Radiative forcing W
! rowspan="2" | Concentrations
over time
up to year 2022 | |||
| Carbon dioxide ppm | 1 | 278 | 365 (1.46) | 379 (1.66) | 391 (1.82) | 410 (2.16) | ||
| Methane ppb | 12.4 | 28 | 700 | 1,745 (0.48) | 1,774 (0.48) | 1,801 (0.48) | 1866 (0.54) | |
| Nitrous oxide 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) | |
| Hexafluoroethane (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) |
The atmospheric lifetime of a greenhouse gas refers to the time required to restore equilibrium following a sudden increase or decrease in its concentration in the atmosphere. Individual atoms or molecules may be lost or deposited to sinks such as the soil, the oceans and other waters, or vegetation and other biological systems, reducing the excess to background concentrations. The average time taken to achieve this is the mean lifetime. This can be represented through the following formula, where the lifetime of an atmospheric chemical species X in a one-box model is the average time that a molecule of X remains in the box.
can also be defined as the ratio of the mass (in kg) of X in the box to its removal rate, which is the sum of the flow of X out of the box (), chemical loss of X (), and deposition of X () (all in kg/s):
If input of this gas into the box ceased, then after time , its concentration would decrease by about 63%.Changes to any of these variables can alter the atmospheric lifetime of a greenhouse gas. For instance, methane's atmospheric lifetime is estimated to have been lower in the 19th century than now, but to have been higher in the second half of the 20th century than after 2000. Carbon dioxide has an even more variable lifetime, which cannot be specified down to a single number. Scientists instead say that while the first 10% of carbon dioxide's airborne fraction (not counting the ~50% absorbed by land and ocean sinks within the emission's first year) is removed "quickly", the vast majority of the airborne fraction – 80% – lasts for "centuries to millennia". The remaining 10% stays for tens of thousands of years. In some models, this longest-lasting fraction is as large as 30%.
There are several different methods of measuring carbon dioxide concentrations in the atmosphere, including infrared analyzing and manometry. Methane and nitrous oxide are measured by other instruments, such as the range-resolved infrared differential absorption lidar (DIAL). Greenhouse gases are measured from space such as by the Orbiting Carbon Observatory and through networks of such as the Integrated Carbon Observation System.
The Annual Greenhouse Gas Index (AGGI) is defined by atmospheric scientists at NOAA as the ratio of total direct radiative forcing due to long-lived and well-mixed greenhouse gases for any year for which adequate global measurements exist, to that present in year 1990. These radiative forcing levels are relative to those present in year 1750 (i.e. prior to the start of the industrial era). 1990 is chosen because it is the baseline year for the Kyoto Protocol, and is the publication year of the first IPCC Scientific Assessment of Climate Change. As such, NOAA states that the AGGI "measures the commitment that (global) society has already made to living in a changing climate. It is based on the highest quality atmospheric observations from sites around the world. Its uncertainty is very low."
If current emission rates continue then temperature rises will surpass sometime between 2040 and 2070, which is the level the United Nations' Intergovernmental Panel on Climate Change (IPCC) says is "dangerous".
Most greenhouse gases have both natural and human-caused sources. An exception are purely human-produced synthetic halocarbons which have no natural sources. During the pre-industrial Holocene, concentrations of existing gases were roughly constant, because the large natural sources and sinks roughly balanced. In the industrial era, human activities have added greenhouse gases to the atmosphere, mainly through the burning of fossil fuels and clearing of forests.
Negative emissions approaches are also being studied for atmospheric methane, called atmospheric methane removal.
During the late 20th century, a scientific consensus evolved that increasing concentrations of greenhouse gases in the atmosphere cause a substantial rise in global temperatures and changes to other parts of the climate system, with consequences for the environment and for human health.
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