Atmospheric concentrations are determined by the balance between sources (emissions of the gas from human activities and natural systems) and sinks (the removal of the gas from the atmosphere by conversion to a different chemical compound or absorption by bodies of water). The proportion of an emission remaining in the atmosphere after a specified time is the "airborne fraction" (AF). The annual airborne fraction is the ratio of the atmospheric increase in a given year to that year's total emissions. As of 2006 the annual airborne fraction for CO2 was about 0.45. The annual airborne fraction increased at a rate of 0.25 ± 0.21% per year over the period 1959–2006.
Indirect radiative effectsEdit
Concentrations of carbon monoxide in the Spring and Fall of 2000 in the lower atmosphere showing a range from about 390 parts per billion (dark brown pixels), to 220 parts per billion (red pixels), to 50 parts per billion (blue pixels).
Oxidation of CO to CO2 directly produces an unambiguous increase in radiative forcing although the reason is subtle. The peak of the thermal IR emission from Earth's surface is very close to a strong vibrational absorption band of CO2 (wavelength 15 microns, or wavenumber 667 cm−1). On the other hand, the single CO vibrational band only absorbs IR at much shorter wavelengths (4.7 microns, or 2145 cm−1), where the emission of radiant energy from Earth's surface is at least a factor of ten lower. Oxidation of methane to CO2, which requires reactions with the OH radical, produces an instantaneous reduction in radiative absorption and emission since CO2 is a weaker greenhouse gas than methane. However, the oxidations of CO and CH 4 are entwined since both consume OH radicals. In any case, the calculation of the total radiative effect includes both direct and indirect forcing.
A second type of indirect effect happens when chemical reactions in the atmosphere involving these gases change the concentrations of greenhouse gases. For example, the destruction of non-methane volatile organic compounds (NMVOCs) in the atmosphere can produce ozone. The size of the indirect effect can depend strongly on where and when the gas is emitted.
Methane has indirect effects in addition to forming CO2. The main chemical that reacts with methane in the atmosphere is the hydroxyl radical (OH), thus more methane means that the concentration of OH goes down. Effectively, methane increases its own atmospheric lifetime and therefore its overall radiative effect. The oxidation of methane can produce both ozone and water; and is a major source of water vapor in the normally dry stratosphere. CO and NMVOCs produce CO2 when they are oxidized. They remove OH from the atmosphere, and this leads to higher concentrations of methane. The surprising effect of this is that the global warming potential of CO is three times that of CO2. The same process that converts NMVOCs to carbon dioxide can also lead to the formation of tropospheric ozone. Halocarbons have an indirect effect because they destroy stratospheric ozone. Finally, hydrogen can lead to ozone production and CH 4 increases as well as producing stratospheric water vapor.
Role of water vaporEdit
Increasing water vapor in the stratosphere at Boulder, Colorado
Water vapor accounts for the largest percentage of the greenhouse effect, between 36% and 66% for clear sky conditions and between 66% and 85% when including clouds. Water vapor concentrations fluctuate regionally, but human activity does not directly affect water vapor concentrations except at local scales, such as near irrigated fields. Indirectly, human activity that increases global temperatures will increase water vapor concentrations, a process known as water vapor feedback. The atmospheric concentration of vapor is highly variable and depends largely on temperature, from less than 0.01% in extremely cold regions up to 3% by mass in saturated air at about 32 °C. (See Relative humidity#Other important facts.)
The average residence time of a water molecule in the atmosphere is only about nine days, compared to years or centuries for other greenhouse gases such as CH 4 and CO2. Water vapor responds to and amplifies effects of the other greenhouse gases. The Clausius–Clapeyron relation establishes that more water vapor will be present per unit volume at elevated temperatures. This and other basic principles indicate that warming associated with increased concentrations of the other greenhouse gases also will increase the concentration of water vapor (assuming that the relative humidity remains approximately constant; modeling and observational studies find that this is indeed so). Because water vapor is a greenhouse gas, this results in further warming and so is a "positive feedback" that amplifies the original warming. Eventually other earth processes[which?] offset these positive feedbacks, stabilizing the global temperature at a new equilibrium and preventing the loss of Earth's water through a Venus-like runaway greenhouse effect.
Contribution of clouds to Earth's greenhouse effectEdit
The major non-gas contributor to Earth's greenhouse effect, clouds, also absorb and emit infrared radiation and thus have an effect on greenhouse gas radiative properties. Clouds are water droplets or ice crystals suspended in the atmosphere.
Impacts on the overall greenhouse effectEdit
Schmidt et al. (2010) analyzed how individual components of the atmosphere contribute to the total greenhouse effect. They estimated that water vapor accounts for about 50% of Earth's greenhouse effect, with clouds contributing 25%, carbon dioxide 20%, and the minor greenhouse gases and aerosols accounting for the remaining 5%. In the study, the reference model atmosphere is for 1980 conditions. Image credit: NASA.
The contribution of each gas to the greenhouse effect is determined by the characteristics of that gas, its abundance, and any indirect effects it may cause. For example, the direct radiative effect of a mass of methane is about 84 times stronger than the same mass of carbon dioxide over a 20-year time frame but it is present in much smaller concentrations so that its total direct radiative effect has so far been smaller, in part due to its shorter atmospheric lifetime in the absence of additional carbon sequestration. On the other hand, in addition to its direct radiative impact, methane has a large, indirect radiative effect because it contributes to ozone formation. Shindell et al. (2005) argues that the contribution to climate change from methane is at least double previous estimates as a result of this effect.
When ranked by their direct contribution to the greenhouse effect, the most important are:[failed verification]
Proportion of direct effects at a given momentEdit
It is not possible to state that a certain gas causes an exact percentage of the greenhouse effect. This is because some of the gases absorb and emit radiation at the same frequencies as others, so that the total greenhouse effect is not simply the sum of the influence of each gas. The higher ends of the ranges quoted are for each gas alone; the lower ends account for overlaps with the other gases. In addition, some gases, such as methane, are known to have large indirect effects that are still being quantified.
Aside from water vapor, which has a residence time of about nine days, major greenhouse gases are well mixed and take many years to leave the atmosphere. Although it is not easy to know with precision how long it takes greenhouse gases to leave the atmosphere, there are estimates for the principal greenhouse gases.
Jacob (1999) defines the lifetime of an atmospheric species X in a one-box model as the average time that a molecule of X remains in the box. Mathematically can
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%.
The atmospheric lifetime of a species therefore measures 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.
Carbon dioxide has a variable atmospheric lifetime, and cannot be specified precisely. Although more than half of the CO2 emitted is removed from the atmosphere within a century, some fraction (about 20%) of emitted CO2 remains in the atmosphere for many thousands to hundreds of thousands of years. Similar issues apply to other greenhouse gases, many of which have longer mean lifetimes than CO2, e.g. N2O has a mean atmospheric lifetime of 121 years.
Radiative forcing and annual greenhouse gas indexEdit
The radiative forcing (warming influence) of long-lived atmospheric greenhouse gases has accelerated, almost doubling in 40 years.
Earth absorbs some of the radiant energy received from the sun, reflects some of it as light and reflects or radiates the rest back to space as heat. A planet's surface temperature depends on this balance between incoming and outgoing energy. When Earth's energy balance is shifted, its surface becomes warmer or cooler, leading to a variety of changes in global climate.
A number of natural and man-made mechanisms can affect the global energy balance and force changes in Earth's climate. Greenhouse gases are one such mechanism. Greenhouse gases absorb and emit some of the outgoing energy radiated from Earth's surface, causing that heat to be retained in the lower atmosphere. As explained above, some greenhouse gases remain in the atmosphere for decades or even centuries, and therefore can affect Earth's energy balance over a long period. Radiative forcing quantifies (in Watts per square meter) the effect of factors that influence Earth's energy balance; including changes in the concentrations of greenhouse gases. Positive radiative forcing leads to warming by increasing the net incoming energy, whereas negative radiative forcing leads to cooling.
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."
The global warming potential (GWP) depends on both the efficiency of the molecule as a greenhouse gas and its atmospheric lifetime. GWP is measured relative to the same mass of CO2 and evaluated for a specific timescale. Thus, if a gas has a high (positive) radiative forcing but also a short lifetime, it will have a large GWP on a 20-year scale but a small one on a 100-year scale. Conversely, if a molecule has a longer atmospheric lifetime than CO2 its GWP will increase when the timescale is considered. Carbon dioxide is defined to have a GWP of 1 over all time periods.
Methane has an atmospheric lifetime of 12 ± 2 years. The 2021 IPCC report lists the GWP as 83 over a time scale of 20 years, 30 over 100 years and 10 over 500 years. A 2014 analysis, however, states that although methane's initial impact is about 100 times greater than that of CO2, because of the shorter atmospheric lifetime, after six or seven decades, the impact of the two gases is about equal, and from then on methane's relative role continues to decline. The decrease in GWP at longer times is because methane decomposes to water and CO2 through chemical reactions in the atmosphere.
Examples of the atmospheric lifetime and GWP relative to CO2 for several greenhouse gases are given in the following table:
Atmospheric lifetime and GWP relative to CO2 at different time horizon for various greenhouse gases
Top: Increasing atmospheric carbon dioxide levels as measured in the atmosphere and reflected in ice cores. Bottom: The amount of net carbon increase in the atmosphere, compared to carbon emissions from burning fossil fuel.
Measurements from ice cores over the past 800,000 yearsEdit
Ice cores provide evidence for greenhouse gas concentration variations over the past 800,000 years (see the following section). Both CO2 and CH 4 vary between glacial and interglacial phases, and concentrations of these gases correlate strongly with temperature. Direct data does not exist for periods earlier than those represented in the ice core record, a record that indicates CO2mole fractions stayed within a range of 180 ppm to 280 ppm throughout the last 800,000 years, until the increase of the last 250 years. However, various proxies and modeling suggests larger variations in past epochs; 500 million years ago CO2 levels were likely 10 times higher than now. Indeed, higher CO2 concentrations are thought to have prevailed throughout most of the PhanerozoicEon, with concentrations four to six times current concentrations during the Mesozoic era, and ten to fifteen times current concentrations during the early Palaeozoic era until the middle of the Devonian period, about 400 Ma. The spread of land plants is thought to have reduced CO2 concentrations during the late Devonian, and plant activities as both sources and sinks of CO2 have since been important in providing stabilizing feedbacks.
Earlier still, a 200-million year period of intermittent, widespread glaciation extending close to the equator (Snowball Earth) appears to have been ended suddenly, about 550 Ma, by a colossal volcanic outgassing that raised the CO2 concentration of the atmosphere abruptly to 12%, about 350 times modern levels, causing extreme greenhouse conditions and carbonate deposition as limestone at the rate of about 1 mm per day. This episode marked the close of the Precambrian Eon, and was succeeded by the generally warmer conditions of the Phanerozoic, during which multicellular animal and plant life evolved. No volcanic carbon dioxide emission of comparable scale has occurred since. In the modern era, emissions to the atmosphere from volcanoes are approximately 0.645 billion tons of CO2 per year, whereas humans contribute 29 billion tons of CO2 each year.
Measurements from Antarctic ice cores
show that before industrial emissions started atmospheric CO2 mole fractions were about 280 parts per million (ppm), and stayed between 260 and 280 during the preceding ten thousand years. Carbon dioxide mole fractions in the atmosphere have gone up by approximately 35 percent since the 1900s, rising from 280 parts per million by volume to 387 parts per million in 2009. One study using evidence from stomata of fossilized leaves suggests greater variability, with carbon dioxide mole fractions above 300 ppm during the period seven to ten thousand years ago, though others have argued that these findings more likely reflect calibration or contamination problems rather than actual CO2 variability. Because of the way air is trapped in ice (pores in the ice close off slowly to form bubbles deep within the firn) and the time period represented in each ice sample analyzed, these figures represent averages of atmospheric concentrations of up to a few centuries rather than annual or decadal levels.
Changes since the Industrial RevolutionEdit
Major greenhouse gas trends.
Since the beginning of the Industrial Revolution, the concentrations of many of the greenhouse gases have increased. For example, the mole fraction of carbon dioxide has increased from 280 ppm to 421 ppm, or 140 ppm over modern pre-industrial levels. The first 30 ppm increase 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.
Recent data also shows that the concentration is increasing at a higher rate. In the 1960s, the average annual increase was only 37% of what it was in 2000 through 2007.
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.
Greenhouse gas emissions from human activitiesEdit
The agriculture, land uses, and other land uses sector, on average, accounted for 13-21% of global total anthropogenic greenhouse gas (GHG) emissions in the period 2010-2019.
Total cumulative emissions from 1870 to 2017 were 425±20 GtC (1539 GtCO2) from fossil fuels and industry, and 180±60 GtC (660 GtCO2) from land use change. Land-use change, such as deforestation, caused about 31% of cumulative emissions over 1870–2017, coal 32%, oil 25%, and gas 10%.
Today,[when?] the stock of carbon in the atmosphere increases by more than 3 million tons per annum (0.04%) compared with the existing stock.[clarification needed] This increase is the result of human activities by burning fossil fuels, deforestation and forest degradation in tropical and boreal regions.
The other greenhouse gases produced from human activity show similar increases in both amount and rate of increase.
The 2021 IPCC Sixth Assessment Report noted that "From a physical science perspective, limiting human-induced global warming to a specific level requires limiting cumulative CO2 emissions, reaching at least net zero CO2 emissions, along with strong reductions in other greenhouse gas emissions. Strong, rapid and sustained reductions in CH4 emissions would also limit the warming effect resulting from declining aerosol pollution and would improve air quality."
The US, China and Russia have cumulatively contributed the greatest amounts of CO2 since 1850.
Since about 1750, human activity has increased the concentration of carbon dioxide and other greenhouse gases. As of 2021, measured atmospheric concentrations of carbon dioxide were almost 50% higher than pre-industrial levels. Natural sources of carbon dioxide are more than 20 times greater than sources due to human activity, but over periods longer than a few years natural sources are closely balanced by natural sinks, mainly photosynthesis of carbon compounds by plants and marine plankton. Absorption of terrestrial infrared radiation by longwave absorbing gases makes Earth a less efficient emitter. Therefore, in order for Earth to emit as much energy as is absorbed, global temperatures must increase.
Burning fossil fuels is estimated to have emitted 62% of 2015 human GhG. The largest single source is coal-fired power stations, with 20% of GHG as of 2021.
a physical change (condensation and precipitation remove water vapor from the atmosphere).
a chemical reaction within the atmosphere. For example, methane is oxidized by reaction with naturally occurring hydroxyl radical, OH· and degraded to CO2 and water vapor (CO2 from the oxidation of methane is not included in the methane Global warming potential). Other chemical reactions include solution and solid phase chemistry occurring in atmospheric aerosols.
a physical exchange between the atmosphere and the other components of the planet. An example is the mixing of atmospheric gases into the oceans.
A number of technologies remove greenhouse gases emissions from the atmosphere. Most widely analyzed are those that remove carbon dioxide from the atmosphere, either to geologic formations such as bio-energy with carbon capture and storage and carbon dioxide air capture, or to the soil as in the case with biochar. The IPCC has pointed out that many long-term climate scenario models require large-scale man-made negative emissions to avoid serious climate change.
History of scientific researchEdit
In the late 19th century, scientists experimentally discovered that N 2 and O 2 do not absorb infrared radiation (called, at that time, "dark radiation"), while water (both as true vapor and condensed in the form of microscopic droplets suspended in clouds) and CO2 and other poly-atomic gaseous molecules do absorb infrared radiation. In the early 20th century, researchers realized that greenhouse gases in the atmosphere made Earth's overall temperature higher than it would be without them. 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.
^ ab"IPCC AR4 SYR Appendix Glossary" (PDF). Archived from the original (PDF) on 17 November 2018. Retrieved 14 December 2008.
^"NASA GISS: Science Briefs: Greenhouse Gases: Refining the Role of Carbon Dioxide". www.giss.nasa.gov. Archived from the original on 12 January 2005. Retrieved 26 April 2016.
^Karl TR, Trenberth KE (2003). "Modern global climate change". Science. 302 (5651): 1719–23. Bibcode:2003Sci...302.1719K. doi:10.1126/science.1090228. PMID14657489. S2CID 45484084. Archived from the original on 22 April 2021. Retrieved 26 July 2019.
^Le Treut H.; Somerville R.; Cubasch U.; Ding Y.; Mauritzen C.; Mokssit A.; Peterson T.; Prather M. Historical overview of climate change science(PDF). Archived (PDF) from the original on 26 November 2018. Retrieved 14 December 2008. in IPCC AR4 WG1 (2007)
^"NASA Science Mission Directorate article on the water cycle". Nasascience.nasa.gov. Archived from the original on 17 January 2009. Retrieved 16 October 2010.
^"Comparing the Greenhouse Effect on Earth, Mars, Venus, and Titan: Present Day and through Time". CiteSeerX10.1.1.673.922.
^ ab"Carbon dioxide now more than 50% higher than pre-industrial levels". National Oceanic and Atmospheric Administration. 3 June 2022. Retrieved 30 August 2022.
^"Climate Change: Atmospheric Carbon Dioxide | NOAA Climate.gov". www.climate.gov. Archived from the original on 24 June 2013. Retrieved 2 March 2020.
^"Global Greenhouse Gas Emissions Data". U.S. Environmental Protection Agency. 12 January 2016. Archived from the original on 5 December 2019. Retrieved 30 December 2019. The burning of coal, natural gas, and oil for electricity and heat is the largest single source of global greenhouse gas emissions.
^"AR4 SYR Synthesis Report Summary for Policymakers – 2 Causes of change". ipcc.ch. Archived from the original on 28 February 2018. Retrieved 9 October 2015.
^"Atmospheric Concentration of Greenhouse Gases" (PDF). U.S. Environmental Protection Agency. 1 August 2016. Archived (PDF) from the original on 19 October 2021. Retrieved 6 September 2021.
^"Inside the Earth's invisible blanket". sequestration.org. Archived from the original on 28 July 2020. Retrieved 5 March 2021.
^Canadell, J.G.; Le Quere, C.; Raupach, M.R.; Field, C.B.; Buitenhuis, E.T.; Ciais, P.; Conway, T.J.; Gillett, N.P.; Houghton, R.A.; Marland, G. (2007). "Contributions to accelerating atmospheric CO2 growth from economic activity, carbon intensity, and efficiency of natural sinks". Proc. Natl. Acad. Sci. USA. 104 (47): 18866–70. Bibcode:2007PNAS..10418866C. doi:10.1073/pnas.0702737104. PMC2141868. PMID17962418.
^"The Chemistry of Earth's Atmosphere". Earth Observatory. NASA. Archived from the original on 20 September 2008.
^ abForster, P.; et al. (2007). "2.10.3 Indirect GWPs". Changes in Atmospheric Constituents and in Radiative Forcing. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press. Archived from the original on 9 February 2019. Retrieved 2 December 2012.
^MacCarty, N. "Laboratory Comparison of the Global-Warming Potential of Six Categories of Biomass Cooking Stoves" (PDF). Approvecho Research Center. Archived from the original (PDF) on 11 November 2013.
^ abc"Water vapour: feedback or forcing?". RealClimate. 6 April 2005. Archived from the original on 24 June 2007. Retrieved 1 May 2006.
^Evans, Kimberly Masters (2005). "The greenhouse effect and climate change". The environment: a revolution in attitudes. Detroit: Thomson Gale. ISBN 978-0787690823.
^"Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2010". U.S. Environmental Protection Agency. 15 April 2012. p. 1.4. Archived from the original on 30 December 2019. Retrieved 30 December 2019.
^ abcKiehl, J.T.; Kevin E. Trenberth (1997). "Earth's annual global mean energy budget". Bulletin of the American Meteorological Society. 78 (2): 197–208. Bibcode:1997BAMS...78..197K. doi:10.1175/1520-0477(1997)078<0197:EAGMEB>2.0.CO;2.
^Schmidt, G.A.; R. Ruedy; R.L. Miller; A.A. Lacis (2010), "The attribution of the present-day total greenhouse effect" (PDF), J. Geophys. Res., vol. 115, no. D20, pp. D20106, Bibcode:2010JGRD..11520106S, doi:10.1029/2010JD014287, archived from the original (PDF) on 22 October 2011, D20106. Web page Archived 4 June 2012 at the Wayback Machine
^Lacis, A. (October 2010), NASA GISS: CO2: The Thermostat that Controls Earth's Temperature, New York: NASA GISS, archived from the original on 20 October 2010
^ abcdefg"Appendix 8.A" (PDF). Intergovernmental Panel on Climate Change Fifth Assessment Report. p. 731. Archived (PDF) from the original on 13 October 2017. Retrieved 6 November 2017.
^Shindell, Drew T. (2005). "An emissions-based view of climate forcing by methane and tropospheric ozone". Geophysical Research Letters. 32 (4): L04803. Bibcode:2005GeoRL..32.4803S. doi:10.1029/2004GL021900. S2CID 129022003. Archived from the original on 11 September 2005. Retrieved 3 September 2005.
^"Methane's Impacts on Climate Change May Be Twice Previous Estimates". Nasa.gov. 30 November 2007. Archived from the original on 11 September 2005. Retrieved 16 October 2010.
^"Climate Change Indicators: Atmospheric Concentrations of Greenhouse Gases". Climate Change Indicators. United States Environmental Protection Agency. 27 June 2016. Archived from the original on 30 April 2016. Retrieved 20 January 2017.
^Wallace, John M. and Peter V. Hobbs. Atmospheric Science; An Introductory Survey. Elsevier. Second Edition, 2006. ISBN 978-0127329512. Chapter 1
^Prather, Michael J.; J Hsu (2008). "NF 3, the greenhouse gas missing from Kyoto". Geophysical Research Letters. 35 (12): L12810. Bibcode:2008GeoRL..3512810P. doi:10.1029/2008GL034542. Archived from the original on 23 September 2019. Retrieved 23 September 2019.
^Isaksen, Ivar S.A.; Michael Gauss; Gunnar Myhre; Katey M. Walter Anthony; Carolyn Ruppel (20 April 2011). "Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions" (PDF). Global Biogeochemical Cycles. 25 (2): n/a. Bibcode:2011GBioC..25.2002I. doi:10.1029/2010GB003845. hdl:1912/4553. S2CID 17810925. Archived from the original (PDF) on 4 March 2016. Retrieved 29 July 2011.
^"AGU Water Vapor in the Climate System". Eso.org. 27 April 1995. Archived from the original on 20 October 2012. Retrieved 11 September 2011.
^Betts (2001). "6.3 Well-mixed Greenhouse Gases". Chapter 6 Radiative Forcing of Climate Change. Working Group I: The Scientific Basis IPCC Third Assessment Report – Climate Change 2001. UNEP/GRID-Arendal – Publications. Archived from the original on 29 June 2011. Retrieved 16 October 2010.
^ abJacob, Daniel (1999). Introduction to atmospheric chemistry. Princeton University Press. pp. 25–26. ISBN 978-0691001852. Archived from the original on 2 September 2011.
^"How long will global warming last?". RealClimate. 15 March 2005. Archived from the original on 4 March 2021. Retrieved 12 June 2012.
^"Frequently Asked Question 10.3: If emissions of greenhouse gases are reduced, how quickly do their concentrations in the atmosphere decrease?". Global Climate Projections. Archived from the original on 24 December 2011. Retrieved 1 June 2011. in IPCC AR4 WG1 (2007)
^See also: Archer, David (2005). "Fate of fossil fuel CO2 in geologic time" (PDF). Journal of Geophysical Research. 110 (C9): C09S05.1–6. Bibcode:2005JGRC..11009S05A. doi:10.1029/2004JC002625. Archived (PDF) from the original on 19 December 2005. Retrieved 27 July 2007.
^See also: Caldeira, Ken; Wickett, Michael E. (2005). "Ocean model predictions of chemistry changes from carbon dioxide emissions to the atmosphere and ocean" (PDF). Journal of Geophysical Research. 110 (C9): C09S04.1–12. Bibcode:2005JGRC..11009S04C. doi:10.1029/2004JC002671. Archived from the original (PDF) on 10 August 2007. Retrieved 27 July 2007.
^"Annual Greenhouse Gas Index". U.S. Global Change Research Program. Archived from the original on 21 April 2021. Retrieved 5 September 2020.
^ abButler J. and Montzka S. (2020). "The NOAA Annual Greenhouse Gas Index (AGGI)". NOAA Global Monitoring Laboratory/Earth System Research Laboratories. Archived from the original on 22 September 2013. Retrieved 5 September 2020.
^ ab"Climate Change Indicators in the United States - Greenhouse Gases". U.S. Environmental Protection Agency (EPA). 2016. Archived from the original on 27 August 2016. Retrieved 5 September 2020..
^"Climate Change Indicators in the United States - Climate Forcing". U.S. Environmental Protection Agency (EPA). 2016. Archived from the original on 27 August 2016. Retrieved 5 September 2020. Archived 21 September 2020 at the Wayback Machine
^LuAnn Dahlman (14 August 2020). "Climate change: annual greenhouse gas index". NOAA Climate.gov science news & Information for a climate smart nation. Archived from the original on 16 August 2013. Retrieved 5 September 2020.
^"The NOAA Annual Greenhouse Gas Index (AGGI) - An Introduction". NOAA Global Monitoring Laboratory/Earth System Research Laboratories. Archived from the original on 27 November 2020. Retrieved 5 September 2020.
^Lynch, Patrick; Putnam, William (18 November 2014). "Simulating Carbon". NASA Visualization Explorer. Goddard Media Studios. Retrieved 16 August 2022.
^Chandler, David L. "How to count methane emissions". MIT News. Archived from the original on 16 January 2015. Retrieved 20 August 2018. Referenced paper is Trancik, Jessika; Edwards, Morgan (25 April 2014). "Climate impacts of energy technologies depend on emissions timing" (PDF). Nature Climate Change. 4 (5): 347. Bibcode:2014NatCC...4..347E. doi:10.1038/nclimate2204. hdl:1721.1/96138. Archived from the original (PDF) on 16 January 2015. Retrieved 15 January 2015.
^"Table 2.14" (PDF). IPCC Fourth Assessment Report. p. 212. Archived (PDF) from the original on 15 December 2007. Retrieved 16 December 2008.
^Vaara, Miska (2003), Use of ozone depleting substances in laboratories, TemaNord, p. 170, ISBN 978-9289308847, archived from the original on 6 August 2011
Ehhalt, D.; et al., "Table 4.1", Atmospheric Chemistry and Greenhouse Gases, archived from the original on 3 January 2013, in IPCC TAR WG1 (2001), pp. 244–45 harvp error: no target: CITEREFIPCC_TAR_WG12001 (help). Referred to by: Blasing (2013). Based on Blasing (2013): Pre-1750 concentrations of CH4,N2O and current concentrations of O3, are taken from Table 4.1 (a) of the IPCC Intergovernmental Panel on Climate Change, 2001. Following the convention of IPCC (2001), inferred global-scale trace-gas concentrations from prior to 1750 are assumed to be practically uninfluenced by human activities such as increasingly specialized agriculture, land clearing, and combustion of fossil fuels. Preindustrial concentrations of industrially manufactured compounds are given as zero. The short atmospheric lifetime of ozone (hours-days) together with the spatial variability of its sources precludes a globally or vertically homogeneous distribution, so that a fractional unit such as parts per billion would not apply over a range of altitudes or geographical locations. Therefore a different unit is used to integrate the varying concentrations of ozone in the vertical dimension over a unit area, and the results can then be averaged globally. This unit is called a Dobson Unit (D.U.), after G.M.B. Dobson, one of the first investigators of atmospheric ozone. A Dobson unit is the amount of ozone in a column that, unmixed with the rest of the atmosphere, would be 10 micrometers thick at standard temperature and pressure.
^Because atmospheric concentrations of most gases tend to vary systematically over the course of a year, figures given represent averages over a 12-month period for all gases except ozone (O3), for which a current global value has been estimated (IPCC, 2001, Table 4.1a). CO2 averages for year 2012 are taken from the National Oceanic and Atmospheric Administration, Earth System Research Laboratory, web site: www.esrl.noaa.gov/gmd/ccgg/trends maintained by Dr. Pieter Tans. For other chemical species, the values given are averages for 2011. These data are found on the CDIAC AGAGE web site: http://cdiac.ornl.gov/ndps/alegage.html Archived 21 January 2013 at the Wayback Machine or the AGAGE home page: http://agage.eas.gatech.edu Archived 7 January 2015 at the Wayback Machine.
Forster, P.; et al., "Table 2.1", Changes in Atmospheric Constituents and in Radiative Forcing, archived from the original on 12 October 2012, retrieved 30 October 2012, in IPCC AR4 WG1 (2007), p. 141. Referred to by: Blasing (2013)
Prentice, I.C.; et al. "Executive summary". The Carbon Cycle and Atmospheric Carbon Dioxide. Archived from the original on 7 December 2009., in IPCC TAR WG1 (2001), p. 185 harvp error: no target: CITEREFIPCC_TAR_WG12001 (help). Referred to by: Blasing (2013)
^"Carbon dioxide levels continue at record levels, despite COVID-19 lockdown". WMO.int. World Meteorological Organization. 23 November 2020. Archived from the original on 1 December 2020.
^IPCC AR4 WG1 (2007), p. 140:"The simple formulae ... in Ramaswamy et al. (2001) are still valid. and give an RF of +3.7 W m–2 for a doubling in the CO2 mixing ratio. ... RF increases logarithmically with mixing ratio" Calculation: ln(new ppm/old ppm)/ln(2)*3.7
^ abcdThe first value in a cell represents Mace Head, Ireland, a mid-latitude Northern-Hemisphere site, while the second value represents Cape Grim, Tasmania, a mid-latitude Southern-Hemisphere site. "Current" values given for these gases are annual arithmetic averages based on monthly background concentrations for year 2011. The SF 6 values are from the AGAGE gas chromatography – mass spectrometer (gc-ms) Medusa measuring system.
^"Advanced Global Atmospheric Gases Experiment (AGAGE)". Archived from the original on 21 January 2013. Retrieved 30 October 2012. Data compiled from finer time scales in the Prinn; etc (2000). "ALE/GAGE/AGAGE database". Archived from the original on 21 January 2013. Retrieved 30 October 2012.
^The pre-1750 value for N 2O is consistent with ice-core records from 10,000 BCE through 1750 CE: "Summary for policymakers", Figure SPM.1, IPCC, archived from the original on 2 November 2018, retrieved 30 October 2012, in IPCC AR4 WG1 (2007), p. 3. Referred to by: Blasing (2013)
^Changes in stratospheric ozone have resulted in a decrease in radiative forcing of 0.05 W/m2: Forster, P.; et al., "Table 2.12", Changes in Atmospheric Constituents and in Radiative Forcing, archived from the original on 28 January 2013, retrieved 30 October 2012, in IPCC AR4 WG1 (2007), p. 204. Referred to by: Blasing (2013)
^"SF 6 data from January 2004". Archived from the original on 21 January 2013. Retrieved 2 January 2013.
^"Data from 1995 through 2004". National Oceanic and Atmospheric Administration (NOAA), Halogenated and other Atmospheric Trace Species (HATS).
^Sturges, W.T.; et al. "Concentrations of SF 6 from 1970 through 1999, obtained from Antarctic firn (consolidated deep snow) air samples". Archived from the original on 21 January 2013. Retrieved 2 January 2013.
^Berner, Robert A. (January 1994). "GEOCARB II: a revised model of atmospheric CO2 over Phanerozoic time" (PDF). American Journal of Science. 294 (1): 56–91. Bibcode:1994AmJS..294...56B. doi:10.2475/ajs.294.1.56.[permanent dead link]
^Berner, Robert A.; Kothavala, Zavareth (2001). "GEOCARB III: a revised model of atmospheric CO2 over Phanerozoic time" (PDF). American Journal of Science. 301 (2): 182–204. Bibcode:2001AmJS..301..182B. CiteSeerX10.1.1.393.582. doi:10.2475/ajs.301.2.182. Archived from the original (PDF) on 6 August 2004.
^Beerling, D.J.; Berner, R.A. (2005). "Feedbacks and the co-evolution of plants and atmospheric CO2". Proc. Natl. Acad. Sci. USA. 102 (5): 1302–05. Bibcode:2005PNAS..102.1302B. doi:10.1073/pnas.0408724102. PMC547859. PMID15668402.
^ abHoffmann, PF; AJ Kaufman; GP Halverson; DP Schrag (1998). "A neoproterozoic snowball earth". Science. 281 (5381): 1342–46. Bibcode:1998Sci...281.1342H. doi:10.1126/science.281.5381.1342. PMID9721097. S2CID 13046760.
^Siegel, Ethan. "How Much CO2 Does A Single Volcano Emit?". Forbes. Archived from the original on 6 June 2017. Retrieved 6 September 2018.
^Gerlach, TM (1991). "Present-day CO2 emissions from volcanoes". Transactions of the American Geophysical Union. 72 (23): 249–55. Bibcode:1991EOSTr..72..249.. doi:10.1029/90EO10192.
^See also: "U.S. Geological Survey". 14 June 2011. Archived from the original on 25 September 2012. Retrieved 15 October 2012.
^Flückiger, Jacqueline (2002). "High-resolution Holocene N 2O ice core record and its relationship with CH 4 and CO2". Global Biogeochemical Cycles. 16 (1): 1010. Bibcode:2002GBioC..16.1010F. doi:10.1029/2001GB001417.
^Friederike Wagner; Bent Aaby; Henk Visscher (2002). "Rapid atmospheric CO2 changes associated with the 8,200-years-B.P. cooling event". Proc. Natl. Acad. Sci. USA. 99 (19): 12011–14. Bibcode:2002PNAS...9912011W. doi:10.1073/pnas.182420699. PMC129389. PMID12202744.
^Andreas Indermühle; Bernhard Stauffer; Thomas F. Stocker (1999). "Early Holocene Atmospheric CO2 Concentrations". Science. 286 (5446): 1815. doi:10.1126/science.286.5446.1815a. IndermÜhle, A (1999). "Early Holocene atmospheric CO2concentrations". Science. 286 (5446): 1815a–15. doi:10.1126/science.286.5446.1815a.
^H. J. Smith; M. Wahlen; D. Mastroianni (1997). "The CO2 concentration of air trapped in GISP2 ice from the Last Glacial Maximum-Holocene transition". Geophysical Research Letters. 24 (1): 1–4. Bibcode:1997GeoRL..24....1S. doi:10.1029/96GL03700. S2CID 129667062.
^Charles J. Kibert (2016). "Background". Sustainable Construction: Green Building Design and Delivery. Wiley. ISBN 978-1119055327.
^"Full Mauna Loa CO2 record". Earth System Research Laboratory. 2005. Archived from the original on 28 April 2017. Retrieved 6 May 2017.
^Tans, Pieter (3 May 2008). "Annual CO2 mole fraction increase (ppm) for 1959–2007". National Oceanic and Atmospheric Administration Earth System Research Laboratory, Global Monitoring Division. "additional details". Archived from the original on 25 December 2018. Retrieved 15 May 2008.; see also Masarie, K.A.; Tans, P.P. (1995). "Extension and integration of atmospheric carbon dioxide data into a globally consistent measurement record". J. Geophys. Res. 100 (D6): 11593–610. Bibcode:1995JGR...10011593M. doi:10.1029/95JD00859. Archived from the original on 8 March 2021. Retrieved 26 July 2019.
^"Historical Overview of Climate Change Science – FAQ 1.3 Figure 1" (PDF). p. 116. Archived (PDF) from the original on 26 November 2018. Retrieved 25 April 2008. in IPCC AR4 WG1 (2007)
^"Chapter 3, IPCC Special Report on Emissions Scenarios, 2000" (PDF). Intergovernmental Panel on Climate Change. 2000. Archived (PDF) from the original on 20 August 2018. Retrieved 16 October 2010.
^Agriculture, Forestry, and Other Land Uses Ch7 from "Climate Change 2022: Mitigation of Climate Change". www.ipcc.ch. Retrieved 6 April 2022.
^"Global Carbon Project (GCP)". www.globalcarbonproject.org. Archived from the original on 4 April 2019. Retrieved 19 May 2019.
Dumitru-Romulus Târziu; Victor-Dan Păcurar (January 2011). "Pădurea, climatul și energia". Rev. pădur. (in Romanian). 126 (1): 34–39. ISSN 1583-7890. 16720. Archived from the original on 16 April 2013. Retrieved 11 June 2012.(webpage has a translation button)
^"Sixth Assessment Report". www.ipcc.ch. Retrieved 18 December 2021.
^Evans, Simon (5 October 2021). "Analysis: Which countries are historically responsible for climate change? / Historical responsibility for climate change is at the heart of debates over climate justice". CarbonBrief.org. Carbon Brief. Archived from the original on 26 October 2021. Source: Carbon Brief analysis of figures from the Global Carbon Project, CDIAC, Our World in Data, Carbon Monitor, Houghton and Nassikas (2017) and Hansis et al (2015).
^Fox, Alex. "Atmospheric Carbon Dioxide Reaches New High Despite Pandemic Emissions Reduction". Smithsonian Magazine. Retrieved 22 June 2021.
^"Climate Change: Causation Archives". EarthCharts. Retrieved 22 June 2021.
^"It's critical to tackle coal emissions – Analysis". IEA. Retrieved 9 October 2021.
^ ab"Geoengineering the climate: science, governance and uncertainty". The Royal Society. 2009. Archived from the original on 7 September 2009. Retrieved 12 September 2009.
^Fischer, B.S.; Nakicenovic, N.; Alfsen, K.; Morlot, J. Corfee; de la Chesnaye, F.; Hourcade, J.-Ch.; Jiang, K.; Kainuma, M.; La Rovere, E.; Matysek, A.; Rana, A.; Riahi, K.; Richels, R.; Rose, S.; van Vuuren, D.; Warren, R., Issues related to mitigation in the long term context(PDF), archived (PDF) from the original on 22 September 2018, retrieved 13 September 2009 in Rogner et al. (2007)
^Arrhenius, Svante (1896). "On the influence of carbonic acid in the air upon the temperature of the ground" (PDF). The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 41 (251): 237–276. doi:10.1080/14786449608620846. Archived (PDF) from the original on 18 November 2020. Retrieved 1 December 2020.
^Arrhenius, Svante (1897). "On the Influence of Carbonic Acid in the Air Upon the Temperature of the Ground". Publications of the Astronomical Society of the Pacific. 9 (54): 14. Bibcode:1897PASP....9...14A. doi:10.1086/121158.
^Cook, J.; Nuccitelli, D.; Green, S.A.; Richardson, M.; Winkler, B.R.; Painting, R.; Way, R.; Jacobs, P.; Skuce, A. (2013). "Quantifying the consensus on anthropogenic global warming in the scientific literature". Environmental Research Letters. 8 (2): 024024. Bibcode:2013ERL.....8b4024C. doi:10.1088/1748-9326/8/2/024024.
Blasing, T.J. (February 2013), Current Greenhouse Gas Concentrations, doi:10.3334/CDIAC/atg.032, archived from the original on 16 July 2011, retrieved 30 October 2012
Chen, D.; Rojas, M.; Samset, B.H.; Cobb, K.; et al. (2021). "Chapter 1: Framing, context, and methods" (PDF). IPCC AR6 WG1 2021. pp. 1–215.
IPCC (2021). Masson-Delmotte, V.; Zhai, P.; Pirani, A.; Connors, S. L.; et al. (eds.). Climate Change 2021: The Physical Science Basis(PDF). Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press (In Press).
IPCC AR4 WG1 (2007), Solomon, S.; Qin, D.; Manning, M.; Chen, Z.; Marquis, M.; Averyt, K.B.; Tignor, M.; Miller, H.L. (eds.), Climate Change 2007: The Physical Science Basis – Contribution of Working Group I (WG1) to the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), Cambridge University Press, ISBN 978-0521880091 (pb: ISBN 978-0521705967)
Rogner, H.-H.; Zhou, D.; Bradley, R.; Crabbé, P.; Edenhofer, O.; Hare, B.; Kuijpers, L.; Yamaguchi, M. (2007), B. Metz; O.R. Davidson; P.R. Bosch; R. Dave; L.A. Meyer (eds.), Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, ISBN 978-0521880114, archived from the original on 21 January 2012, retrieved 14 January 2012
Media related to Greenhouse gases at Wikimedia Commons
Carbon Dioxide Information Analysis Center (CDIAC), U.S. Department of Energy, retrieved 26 July 2020
The official greenhouse gas emissions data of developed countries from the UNFCCC