Drivers of climate change from 1850–1900 to 2010–2019. Future global warming potential for long lived drivers like carbon dioxide emissions is not represented.

The scientific community has been investigating the causes of climate change for decades. After thousands of studies, it came to a consensus, where it is "unequivocal that human influence has warmed the atmosphere, ocean and land since pre-industrial times."[1]: 3  This consensus is supported by around 200 scientific organizations worldwide,[2] The dominant role in this climate change has been played by the direct emissions of carbon dioxide from the burning of fossil fuels. Indirect CO2 emissions from land use change, and the emissions of methane, nitrous oxide and other greenhouse gases play major supporting roles.[1]

Observed temperature from NASA[3] vs the 1850–1900 average used by the IPCC as a pre-industrial baseline.[4] The primary driver for increased global temperatures in the industrial era is human activity, with natural forces adding variability.[5]

The warming from the greenhouse effect has a logarithmic relationship with the concentration of greenhouse gases. This means that every additional fraction of CO2 and the other greenhouse gases in the atmosphere has a slightly smaller warming effect than the fractions before it as the total concentration increases. However, only around half of CO2 emissions continually reside in the atmosphere in the first place, as the other half is quickly absorbed by carbon sinks in the land and oceans.[6]: 450  Further, the warming per unit of greenhouse gases is also affected by feedbacks, such as the changes in water vapor concentrations or Earth's albedo (reflectivity).[7]: 2233 

As the warming from CO2 increases, carbon sinks absorb a smaller fraction of total emissions, while the "fast" climate change feedbacks amplify greenhouse gas warming. Thus, both effects are considered to each other out, and the warming from each unit of CO2 emitted by humans increases temperature in linear proportion to the total amount of emissions.[8]: 746  Further, some fraction of the greenhouse warming has been "masked" by the human-caused emissions of sulfur dioxide, which forms aerosols that have a cooling effect. However, this masking has been receding in the recent years, due to measures to combat acid rain and air pollution caused by sulfates.[9][10]

Factors affecting Earth's climate

A diagram which shows where the extra heat retained on Earth due to the energy imbalance is going.

A forcing is something that is imposed externally on the climate system. External forcings include natural phenomena such as volcanic eruptions and variations in the sun's output.[11] Human activities can also impose forcings, for example, through changing the composition of Earth's atmosphere. Radiative forcing is a measure of how various factors alter the energy balance of planet Earth.[12] A positive radiative forcing will lead towards a warming of the surface and, over time, the climate system. Between the start of the Industrial Revolution in 1750, and the year 2005, the increase in the atmospheric concentration of carbon dioxide (chemical formula: CO2) led to a positive radiative forcing, averaged over the Earth's surface area, of about 1.66 watts per square metre (abbreviated W m−2).[13]

Climate feedbacks can either amplify or dampen the response of the climate to a given forcing.[14]: 7  There are many feedback mechanisms in the climate system that can either amplify (a positive feedback) or diminish (a negative feedback) the effects of a change in climate forcing.

The climate system will vary in response to changes in forcings.[15] The climate system will show internal variability both in the presence and absence of forcings imposed on it. This internal variability is a result of complex interactions between components of the climate system, such as the coupling between the atmosphere and ocean.[16] An example of internal variability is the El Niño–Southern Oscillation.

Human-caused influences

Energy flows between space, the atmosphere, and Earth's surface. Rising greenhouse gas levels are contributing to an energy imbalance.

Factors affecting Earth's climate can be broken down into forcings, feedbacks and internal variations.[14]: 7  Four main lines of evidence support the dominant role of human activities in recent climate change:[17]

  1. A physical understanding of the climate system: greenhouse gas concentrations have increased and their warming properties are well-established.
  2. There are historical estimates of past climate changes suggest that the recent changes in global surface temperature are unusual.
  3. Advanced climate models are unable to replicate the observed warming unless human greenhouse gas emissions are included.
  4. Observations of natural forces, such as solar and volcanic activity) show that cannot explain the observed warming. For example, an increase in solar activity would have warmed the entire atmosphere, yet only the lower atmosphere has warmed.[18]

Greenhouse gases

Warming influence of atmospheric greenhouse gases has nearly doubled since 1979, with carbon dioxide and methane being the dominant drivers.[19]

Main articles: Greenhouse gas, Greenhouse gas emissions, and Greenhouse effect

Greenhouse gases are transparent to sunlight, and thus allow it to pass through the atmosphere to heat the Earth's surface. The Earth radiates it as heat, and greenhouse gases absorb a portion of it. This absorption slows the rate at which heat escapes into space, trapping heat near the Earth's surface and warming it over time.[20] While water vapour and clouds are the biggest contributors to the greenhouse effect, they primarily change as a function of temperature. Therefore, they are considered to be feedbacks that change climate sensitivity. On the other hand, gases such as CO2, tropospheric ozone,[21] CFCs and nitrous oxide are added or removed independently from temperature. Hence, they are considered to be external forcings that change global temperatures.[22][23]: 742 

CO2 concentrations over the last 800,000 years as measured from ice cores[24][25][26][27] (blue/green) and directly[28] (black)

Human activity since the Industrial Revolution (about 1750), mainly extracting and burning fossil fuels (coal, oil, and natural gas), has increased the amount of greenhouse gases in the atmosphere, resulting in a radiative imbalance. Over the past 150 years human activities have released increasing quantities of greenhouse gases into the atmosphere. By 2019, the concentrations of CO2 and methane had increased by about 48% and 160%, respectively, since 1750.[29] These CO2 levels are higher than they have been at any time during the last 2 million years. Concentrations of methane are far higher than they were over the last 800,000 years.[30]

This has led to increases in mean global temperature, or global warming. The likely range of human-induced surface-level air warming by 2010–2019 compared to levels in 1850–1900 is 0.8 °C to 1.3 °C, with a best estimate of 1.07 °C. This is close to the observed overall warming during that time of 0.9 °C to 1.2 °C. Temperature changes during that time were likely only ±0.1 °C due to natural forcings and ±0.2 °C due to variability in the climate.[31]: 3, 443 

Global anthropogenic greenhouse gas emissions in 2019 were equivalent to 59 billion tonnes of CO2. Of these emissions, 75% was CO2, 18% was methane, 4% was nitrous oxide, and 2% was fluorinated gases.[32]: 7 

Carbon dioxide

Main article: Carbon dioxide in Earth's atmosphere

The Global Carbon Project shows how additions to CO2 since 1880 have been caused by different sources ramping up one after another.

CO2 emissions primarily come from burning fossil fuels to provide energy for transport, manufacturing, heating, and electricity.[33] Additional CO2 emissions come from deforestation and industrial processes, which include the CO2 released by the chemical reactions for making cement, steel, aluminum, and fertiliser.[34]

CO2 is absorbed and emitted naturally as part of the carbon cycle, through animal and plant respiration, volcanic eruptions, and ocean-atmosphere exchange.[35] Human activities, such as the burning of fossil fuels and changes in land use (see below), release large amounts of carbon to the atmosphere, causing CO2 concentrations in the atmosphere to rise.[35][36]

The Keeling Curve shows the long-term increase of atmospheric carbon dioxide (CO2) concentrations since 1958.

The high-accuracy measurements of atmospheric CO2 concentration, initiated by Charles David Keeling in 1958, constitute the master time series documenting the changing composition of the atmosphere.[37] These data, known as the Keeling Curve, have iconic status in climate change science as evidence of the effect of human activities on the chemical composition of the global atmosphere.[37]

Keeling's initial 1958 measurements showed 313 parts per million by volume (ppm). Atmospheric CO2 concentrations, commonly written "ppm", are measured in parts-per-million by volume (ppmv). In May 2019, the concentration of CO2 in the atmosphere reached 415 ppm. The last time when it reached this level was 2.6–5.3 million years ago. Without human intervention, it would be 280 ppm.[38]

In 2022-2024, the concentration of CO2 in the atmosphere increased faster than ever before according to National Oceanic and Atmospheric Administration, as a result of sustained emissions and El Nino conditions.[39]

Methane and nitrous oxide

Main sources of global methane emissions (2008-2017) according to the Global Carbon Project[40]

Methane emissions come from livestock, manure, rice cultivation, landfills, wastewater, and coal mining, as well as oil and gas extraction.[41] Nitrous oxide emissions largely come from the microbial decomposition of fertiliser.[42]

Methane and to a lesser extent nitrous oxide are also major forcing contributors to the greenhouse effect. The Kyoto Protocol lists these together with hydrofluorocarbon (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6),[43] which are entirely artificial gases, as contributors to radiative forcing. The chart at right attributes anthropogenic greenhouse gas emissions to eight main economic sectors, of which the largest contributors are power stations (many of which burn coal or other fossil fuels), industrial processes, transportation fuels (generally fossil fuels), and agricultural by-products (mainly methane from enteric fermentation and nitrous oxide from fertilizer use).[44]

Aerosols

Air pollution has substantially increased the presence of aerosols in the atmosphere when compared to the preindustrial background levels. Different types of particles have different effects, but overall, cooling from aerosols formed by sulfur dioxide emissions has the overwhelming impact. However, the complexity of aerosol interactions in atmospheric layers makes the exact strength of cooling very difficult to estimate.[45]

Air pollution, in the form of aerosols, affects the climate on a large scale.[46][47] Aerosols scatter and absorb solar radiation. From 1961 to 1990, a gradual reduction in the amount of sunlight reaching the Earth's surface was observed. This phenomenon is popularly known as global dimming,[48] and is primarily attributed to sulfate aerosols produced by the combustion of fossil fuels with heavy sulfur concentrations like coal and bunker fuel.[9] Smaller contributions come from black carbon, organic carbon from combustion of fossil fuels and biofuels, and from anthropogenic dust.[49][50][51][52][53] Globally, aerosols have been declining since 1990 due to pollution controls, meaning that they no longer mask greenhouse gas warming as much.[54][9]

Aerosols also have indirect effects on the Earth's energy budget. Sulfate aerosols act as cloud condensation nuclei and lead to clouds that have more and smaller cloud droplets. These clouds reflect solar radiation more efficiently than clouds with fewer and larger droplets.[55] They also reduce the growth of raindrops, which makes clouds more reflective to incoming sunlight.[56] Indirect effects of aerosols are the largest uncertainty in radiative forcing.[57]

While aerosols typically limit global warming by reflecting sunlight, black carbon in soot that falls on snow or ice can contribute to global warming. Not only does this increase the absorption of sunlight, it also increases melting and sea-level rise.[58] Limiting new black carbon deposits in the Arctic could reduce global warming by 0.2 °C by 2050.[59]

Land surface changes

Further information: Climate change § Land surface changes

The rate of global tree cover loss has approximately doubled since 2001, to an annual loss approaching an area the size of Italy.[60]

According to Food and Agriculture Organization, around 30% of Earth's land area is largely unusable for humans (glaciers, deserts, etc.), 26% is forests, 10% is shrubland and 34% is agricultural land.[61] Deforestation is the main land use change contributor to global warming,[62] Between 1750 and 2007, about one-third of anthropogenic CO2 emissions were from changes in land use - primarily from the decline in forest area and the growth in agricultural land.[63] primarily deforestation.[64] as the destroyed trees release CO2, and are not replaced by new trees, removing that carbon sink.[65] Between 2001 and 2018, 27% of deforestation was from permanent clearing to enable agricultural expansion for crops and livestock. Another 24% has been lost to temporary clearing under the shifting cultivation agricultural systems. 26% was due to logging for wood and derived products, and wildfires have accounted for the remaining 23%.[66] Some forests have not been fully cleared, but were already degraded by these impacts. Restoring these forests also recovers their potential as a carbon sink.[67]

Cumulative land-use change contributions to CO2 emissions, by region.[32]: Figure SPM.2b 

Local vegetation cover impacts how much of the sunlight gets reflected back into space (albedo), and how much heat is lost by evaporation. For instance, the change from a dark forest to grassland makes the surface lighter, causing it to reflect more sunlight. Deforestation can also modify the release of chemical compounds that influence clouds, and by changing wind patterns.[68] In tropic and temperate areas the net effect is to produce significant warming, and forest restoration can make local temperatures cooler.[67] At latitudes closer to the poles, there is a cooling effect as forest is replaced by snow-covered (and more reflective) plains.[68] Globally, these increases in surface albedo have been the dominant direct influence on temperature from land use change. Thus, land use change to date is estimated to have a slight cooling effect.[69]

Livestock-associated emissions

See also: Greenhouse gas emissions from agriculture

Meat from cattle and sheep have the highest emissions intensity of any agricultural commodity.

More than 18% of anthropogenic greenhouse gas emissions are attributed to livestock and livestock-related activities such as deforestation and increasingly fuel-intensive farming practices.[70] Specific attributions to the livestock sector include:

Ripple effects

Carbon sinks

CO2 sources and sinks since 1880. While there is little debate that excess carbon dioxide in the industrial era has mostly come from burning fossil fuels, the future strength of land and ocean carbon sinks is an area of study.[71]

The Earth's surface absorbs CO2 as part of the carbon cycle. Despite the contribution of deforestation to greenhouse gas emissions, the Earth's land surface, particularly its forests, remain a significant carbon sink for CO2. Land-surface sink processes, such as carbon fixation in the soil and photosynthesis, remove about 29% of annual global CO2 emissions.[72] The ocean also serves as a significant carbon sink via a two-step process. First, CO2 dissolves in the surface water. Afterwards, the ocean's overturning circulation distributes it deep into the ocean's interior, where it accumulates over time as part of the carbon cycle. Over the last two decades, the world's oceans have absorbed 20 to 30% of emitted CO2.[6]: 450  Thus, around half of human-caused CO2 emissions have been absorbed by land plants and by the oceans.[73]

This fraction of absorbed emissions is not static. If future CO2 emissions decrease, the Earth will be able to absorb up to around 70%. If they increase substantially, it'll still absorb more carbon than now, but the overall fraction will decrease to below 40%.[74] This is because climate change increases droughts and heat waves that eventually inhibit plant growth on land, and soils will release more carbon from dead plants when they are warmer.[75][76] The rate at which oceans absorb atmospheric carbon will be lowered as they become more acidic and experience changes in thermohaline circulation and phytoplankton distribution.[77][78][79]

Climate change feedbacks

Main articles: Climate change feedback and Climate sensitivity

Sea ice reflects 50% to 70% of incoming sunlight, while the ocean, being darker, reflects only 6%. As an area of sea ice melts and exposes more ocean, more heat is absorbed by the ocean, raising temperatures that melt still more ice. This is a positive feedback process.[80]

The response of the climate system to an initial forcing is modified by feedbacks: increased by "self-reinforcing" or "positive" feedbacks and reduced by "balancing" or "negative" feedbacks.[81] The main reinforcing feedbacks are the water-vapour feedback, the ice–albedo feedback, and the net effect of clouds.[82][83] The primary balancing mechanism is radiative cooling, as Earth's surface gives off more heat to space in response to rising temperature.[84] In addition to temperature feedbacks, there are feedbacks in the carbon cycle, such as the fertilizing effect of CO2 on plant growth.[85]

Uncertainty over feedbacks, particularly cloud cover,[86] is the major reason why different climate models project different magnitudes of warming for a given amount of emissions.[87] As air warms, it can hold more moisture. Water vapour, as a potent greenhouse gas, holds heat in the atmosphere.[82] If cloud cover increases, more sunlight will be reflected back into space, cooling the planet. If clouds become higher and thinner, they act as an insulator, reflecting heat from below back downwards and warming the planet.[88]

Another major feedback is the reduction of snow cover and sea ice in the Arctic, which reduces the reflectivity of the Earth's surface.[89] More of the Sun's energy is now absorbed in these regions, contributing to amplification of Arctic temperature changes.[90] Arctic amplification is also thawing permafrost, which releases methane and CO2 into the atmosphere.[91] Climate change can also cause methane releases from wetlands, marine systems, and freshwater systems.[92] Overall, climate feedbacks are expected to become increasingly positive.[93]

Natural variability

The Fourth National Climate Assessment ("NCA4", USGCRP, 2017) includes charts illustrating that neither solar nor volcanic activity can explain the observed warming.[94] [95]

See also: Climate change denial and History of climate change science § Discredited theories and reconciled apparent discrepancies

Already in 2001, the IPCC Third Assessment Report had found that, "The combined change in radiative forcing of the two major natural factors (solar variation and volcanic aerosols) is estimated to be negative for the past two, and possibly the past four, decades."[96] Solar irradiance has been measured directly by satellites,[97] and indirect measurements are available from the early 1600s onwards.[57] Yet, since 1880, there has been no upward trend in the amount of the Sun's energy reaching the Earth, in contrast to the warming of the lower atmosphere (the troposphere).[98] Similarly, volcanic activity has the single largest natural impact (forcing) on temperature, yet it is equivalent to less than 1% of current human-caused CO2 emissions.[99] Volcanic activity as a whole has had negligible impacts on global temperature trends since the Industrial Revolution.[100]

Between 1750 and 2007, solar radiation may have at most increased by 0.12 W/m2, compared to 1.6 W/m2 for the net anthropogenic forcing.[101]: 3  Consequently, the observed rapid rise in global mean temperatures seen after 1985 cannot be ascribed to solar variability."[102] Further, the upper atmosphere (the stratosphere) would also be warming if the Sun was sending more energy to Earth, but instead, it has been cooling.[103] This is consistent with greenhouse gases preventing heat from leaving the Earth's atmosphere.[104]

Explosive volcanic eruptions can release gases, dust and ash that partially block sunlight and reduce temperatures, or they can send water vapor into the atmosphere, which adds to greenhouse gases and increases temperatures.[105] Because both water vapor and volcanic material have low persistence in the atmosphere, even the largest eruptions only have an effect for several years.[106]

See also

References

  1. ^ a b Eyring, Veronika; Gillett, Nathan P.; Achutarao, Krishna M.; Barimalala, Rondrotiana; et al. (2021). "Chapter 3: Human influence on the climate system" (PDF). IPCC AR6 WG1 2021.
  2. ^ OPR (n.d.), Office of Planning and Research (OPR) List of Organizations, OPR, Office of the Governor, State of California, archived from the original on 1 April 2014, retrieved 30 November 2013. Archived page: The source appears to incorrectly list the Society of Biology (UK) twice.
  3. ^ "Global Annual Mean Surface Air Temperature Change". NASA. Archived from the original on 16 April 2020. Retrieved 23 February 2020..
  4. ^ IPCC AR5 SYR Glossary 2014, p. 124.
  5. ^ USGCRP Chapter 3 2017 Figure 3.1 panel 2 Archived 9 April 2018 at the Wayback Machine, Figure 3.3 panel 5 .
  6. ^ a b Bindoff, N.L., W.W.L. Cheung, J.G. Kairo, J. Arístegui, V.A. Guinder, R. Hallberg, N. Hilmi, N. Jiao, M.S. Karim, L. Levin, S. O’Donoghue, S.R. Purca Cuicapusa, B. Rinkevich, T. Suga, A. Tagliabue, and P. Williamson, 2019: Chapter 5: Changing Ocean, Marine Ecosystems, and Dependent Communities. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 447–587. https://doi.org/10.1017/9781009157964.007.
  7. ^ IPCC, 2021: Annex VII: Glossary [Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V. Masson-Delmotte, C.  Méndez, S. Semenov, A. Reisinger (eds.)]. 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, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 2215–2256, doi:10.1017/9781009157896.022.
  8. ^ Canadell, J. G.; Monteiro, P. M. S.; Costa, M. H.; Cotrim da Cunha, L.; Ishii, M.; Jaccard, S.; Cox, P. M.; Eliseev, A. V.; Henson, S.; Koven, C.; Lohila, A.; Patra, P. K.; Piao, S.; Rogelj, J.; Syampungani, S.; Zaehle, S.; Zickfeld, K. (2021). "Global Carbon and Other Biogeochemical Cycles and Feedbacks" (PDF). IPCC AR6 WG1 2021.
  9. ^ a b c Quaas, Johannes; Jia, Hailing; Smith, Chris; Albright, Anna Lea; Aas, Wenche; Bellouin, Nicolas; Boucher, Olivier; Doutriaux-Boucher, Marie; Forster, Piers M.; Grosvenor, Daniel; Jenkins, Stuart; Klimont, Zbigniew; Loeb, Norman G.; Ma, Xiaoyan; Naik, Vaishali; Paulot, Fabien; Stier, Philip; Wild, Martin; Myhre, Gunnar; Schulz, Michael (21 September 2022). "Robust evidence for reversal of the trend in aerosol effective climate forcing". Atmospheric Chemistry and Physics. 22 (18): 12221–12239. Bibcode:2022ACP....2212221Q. doi:10.5194/acp-22-12221-2022. hdl:20.500.11850/572791. S2CID 252446168.
  10. ^ Cao, Yang; Zhu, Yannian; Wang, Minghuai; Rosenfeld, Daniel; Liang, Yuan; Liu, Jihu; Liu, Zhoukun; Bai, Heming (7 January 2023). "Emission Reductions Significantly Reduce the Hemispheric Contrast in Cloud Droplet Number Concentration in Recent Two Decades". Journal of Geophysical Research: Atmospheres. 128 (2): e2022JD037417. Bibcode:2023JGRD..12837417C. doi:10.1029/2022JD037417.
  11. ^ Le Treut et al., Chapter 1: Historical Overview of Climate Change Science Archived 21 December 2011 at the Wayback Machine, FAQ 1.1, What Factors Determine Earth's Climate? Archived 26 June 2011 at the Wayback Machine, in IPCC AR4 WG1 2007.
  12. ^ Forster et al., Chapter 2: Changes in Atmospheric Constituents and Radiative Forcing Archived 21 December 2011 at the Wayback Machine, FAQ 2.1, How do Human Activities Contribute to Climate Change and How do They Compare with Natural Influences? Archived 6 July 2011 at the Wayback Machine in IPCC AR4 WG1 2007.
  13. ^ IPCC, Summary for Policymakers Archived 2 November 2018 at the Wayback Machine, Human and Natural Drivers of Climate Change Archived 2 November 2018 at the Wayback Machine, Figure SPM.2, in IPCC AR4 WG1 2007.
  14. ^ a b US National Research Council (2008). Understanding and responding to climate change: Highlights of National Academies Reports, 2008 edition (PDF). Washington D.C.: National Academy of Sciences. Archived from the original (PDF) on 13 December 2011. Retrieved 20 May 2011.
  15. ^ Committee on the Science of Climate Change, US National Research Council (2001). "2. Natural Climatic Variations". Climate Change Science: An Analysis of Some Key Questions. Washington, D.C., US: National Academies Press. p. 8. doi:10.17226/10139. ISBN 0-309-07574-2. Archived from the original on 27 September 2011. Retrieved 20 May 2011.
  16. ^ Albritton et al., Technical Summary Archived 24 December 2011 at the Wayback Machine, Box 1: What drives changes in climate? Archived 19 January 2017 at the Wayback Machine, in IPCC TAR WG1 2001.
  17. ^ "EPA's Endangerment Finding Climate Change Facts". National Service Center for Environmental Publications (NSCEP). 2009. Report ID: 430F09086. Archived from the original on 23 December 2017. Retrieved 22 December 2017.
  18. ^ USGCRP 2009, p. 20.
  19. ^ "The NOAA Annual Greenhouse Gas Index (AGGI)". NOAA.gov. National Oceanic and Atmospheric Administration (NOAA). Spring 2023. Archived from the original on 24 May 2023.
  20. ^ NASA. "The Causes of Climate Change". Climate Change: Vital Signs of the Planet. Archived from the original on 8 May 2019. Retrieved 8 May 2019.
  21. ^ Wang, Bin; Shugart, Herman H; Lerdau, Manuel T (1 August 2017). "Sensitivity of global greenhouse gas budgets to tropospheric ozone pollution mediated by the biosphere". Environmental Research Letters. 12 (8): 084001. Bibcode:2017ERL....12h4001W. doi:10.1088/1748-9326/aa7885. ISSN 1748-9326. Ozone acts as a greenhouse gas in the lowest layer of the atmosphere, the troposphere (as opposed to the stratospheric ozone layer)
  22. ^ Schmidt, Gavin A.; Ruedy, Reto A.; Miller, Ron L.; Lacis, Andy A. (27 October 2010). "Attribution of the present-day total greenhouse effect". Journal of Geophysical Research: Atmospheres. 115 (D20). Bibcode:2010JGRD..11520106S. doi:10.1029/2010JD014287. ISSN 0148-0227.
  23. ^ Walsh, J., D. Wuebbles, K. Hayhoe, J. Kossin, K. Kunkel, G. Stephens, P. Thorne, R. Vose, M. Wehner, J. Willis, D. Anderson, V. Kharin, T. Knutson, F. Landerer, T. Lenton, J. Kennedy, and R. Somerville, 2014: Appendix 3: Climate Science Supplement. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 735-789. doi:10.7930/J0KS6PHH
  24. ^ Lüthi, Dieter; Le Floch, Martine; Bereiter, Bernhard; Blunier, Thomas; Barnola, Jean-Marc; Siegenthaler, Urs; Raynaud, Dominique; Jouzel, Jean; Fischer, Hubertus; Kawamura, Kenji; Stocker, Thomas F. (May 2005). "High-resolution carbon dioxide concentration record 650,000–800,000 years before present". Nature. 453 (7193): 379–382. Bibcode:2008Natur.453..379L. doi:10.1038/nature06949. ISSN 0028-0836. PMID 18480821. S2CID 1382081.
  25. ^ Fischer, Hubertus; Wahlen, Martin; Smith, Jesse; Mastroianni, Derek; Deck, Bruce (12 March 1999). "Ice Core Records of Atmospheric CO 2 Around the Last Three Glacial Terminations". Science. 283 (5408): 1712–1714. Bibcode:1999Sci...283.1712F. doi:10.1126/science.283.5408.1712. ISSN 0036-8075. PMID 10073931.
  26. ^ Indermühle, Andreas; Monnin, Eric; Stauffer, Bernhard; Stocker, Thomas F.; Wahlen, Martin (1 March 2000). "Atmospheric CO 2 concentration from 60 to 20 kyr BP from the Taylor Dome Ice Core, Antarctica". Geophysical Research Letters. 27 (5): 735–738. Bibcode:2000GeoRL..27..735I. doi:10.1029/1999GL010960. S2CID 18942742.
  27. ^ Etheridge, D.; Steele, L.; Langenfelds, R.; Francey, R.; Barnola, J.-M.; Morgan, V. (1998). "Historical CO2 Records from the Law Dome DE08, DE08-2, and DSS Ice Cores". Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory. U.S. Department of Energy. Retrieved 20 November 2022.
  28. ^ Keeling, C.; Whorf, T. (2004). "Atmospheric CO2 Records from Sites in the SIO Air Sampling Network". Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory. U.S. Department of Energy. Retrieved 20 November 2022.
  29. ^ WMO 2021, p. 8.
  30. ^ IPCC AR6 WG1 Technical Summary 2021, p. TS-35.
  31. ^ The IPCC in this report uses "likely" to indicate a statement with an assessed probability of 66% to 100%.IPCC (2021). "Summary for Policymakers" (PDF). IPCC AR6 WG1 2021. p. 4 n.4. ISBN 978-92-9169-158-6.
  32. ^ a b IPCC, 2022: Summary for Policymakers [P.R. Shukla, J. Skea, A. Reisinger, R. Slade, R. Fradera, M. Pathak, A. Al Khourdajie, M. Belkacemi, R. van Diemen, A. Hasija, G. Lisboa, S. Luz, J. Malley, D. McCollum, S. Some, P. Vyas, (eds.)]. In: Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [P.R. Shukla, J. Skea, R. Slade, A. Al Khourdajie, R. van Diemen, D. McCollum, M. Pathak, S. Some, P. Vyas, R. Fradera, M. Belkacemi, A. Hasija, G. Lisboa, S. Luz, J. Malley, (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA. doi: 10.1017/9781009157926.001.
  33. ^ Ritchie, Hannah (18 September 2020). "Sector by sector: where do global greenhouse gas emissions come from?". Our World in Data. Retrieved 28 October 2020.
  34. ^ Olivier & Peters 2019, p. 17; Our World in Data, 18 September 2020; EPA 2020: Greenhouse gas emissions from industry primarily come from burning fossil fuels for energy, as well as greenhouse gas emissions from certain chemical reactions necessary to produce goods from raw materials; "Redox, extraction of iron and transition metals". Hot air (oxygen) reacts with the coke (carbon) to produce carbon dioxide and heat energy to heat up the furnace. Removing impurities: The calcium carbonate in the limestone thermally decomposes to form calcium oxide. calcium carbonate → calcium oxide + carbon dioxide; Kvande 2014: Carbon dioxide gas is formed at the anode, as the carbon anode is consumed upon reaction of carbon with the oxygen ions from the alumina (Al2O3). Formation of carbon dioxide is unavoidable as long as carbon anodes are used, and it is of great concern because CO2 is a greenhouse gas
  35. ^ a b US Environmental Protection Agency (EPA) (28 June 2012). "Causes of Climate Change: The Greenhouse Effect causes the atmosphere to retain heat". EPA. Archived from the original on 8 March 2017. Retrieved 1 July 2013.
  36. ^ See also: 2.1 Greenhouse Gas Emissions and Concentrations, vol. 2. Validity of Observed and Measured Data, archived from the original on 27 August 2016, retrieved 1 July 2013, in EPA 2009
  37. ^ a b Le Treut, H.; et al., "1.3.1 The Human Fingerprint on Greenhouse Gases", Historical Overview of Climate Change Science, archived from the original on 29 December 2011, retrieved 18 August 2012, in IPCC AR4 WG1 2007.
  38. ^ Rosane, Olivia (13 May 2019). "CO2 Levels Top 415 PPM for First Time in Human History". Ecowatch. Archived from the original on 14 May 2019. Retrieved 14 May 2019.
  39. ^ "During a year of extremes, carbon dioxide levels surge faster than ever". Home National Oceanic and Atmospheric Administration. Retrieved 2 July 2024.
  40. ^ Saunois, M.; Stavert, A.R.; Poulter, B.; et al. (15 July 2020). "The Global Methane Budget 2000–2017". Earth System Science Data (ESSD). 12 (3): 1561–1623. Bibcode:2020ESSD...12.1561S. doi:10.5194/essd-12-1561-2020. ISSN 1866-3508. Retrieved 28 August 2020.
  41. ^ EPA 2020; Global Methane Initiative 2020: Estimated Global Anthropogenic Methane Emissions by Source, 2020: Enteric fermentation (27%), Manure Management (3%), Coal Mining (9%), Municipal Solid Waste (11%), Oil & Gas (24%), Wastewater (7%), Rice Cultivation (7%)
  42. ^ EPA 2019: Agricultural activities, such as fertilizer use, are the primary source of N2O emissions; Davidson 2009: 2.0% of manure nitrogen and 2.5% of fertilizer nitrogen was converted to nitrous oxide between 1860 and 2005; these percentage contributions explain the entire pattern of increasing nitrous oxide concentrations over this period
  43. ^ "The Kyoto Protocol". UNFCCC. Archived from the original on 25 August 2009. Retrieved 9 September 2007.
  44. ^ 7. Projecting the Growth of Greenhouse-Gas Emissions (PDF), pp. 171–4, archived from the original (PDF) on 4 November 2012, in Stern Review Report on the Economics of Climate Change (pre-publication edition) (2006)
  45. ^ Bellouin, N.; Quaas, J.; Gryspeerdt, E.; Kinne, S.; Stier, P.; Watson-Parris, D.; Boucher, O.; Carslaw, K. S.; Christensen, M.; Daniau, A.-L.; Dufresne, J.-L.; Feingold, G.; Fiedler, S.; Forster, P.; Gettelman, A.; Haywood, J. M.; Lohmann, U.; Malavelle, F.; Mauritsen, T.; McCoy, D. T.; Myhre, G.; Mülmenstädt, J.; Neubauer, D.; Possner, A.; Rugenstein, M.; Sato, Y.; Schulz, M.; Schwartz, S. E.; Sourdeval, O.; Storelvmo, T.; Toll, V.; Winker, D.; Stevens, B. (1 November 2019). "Bounding Global Aerosol Radiative Forcing of Climate Change". Reviews of Geophysics. 58 (1): e2019RG000660. doi:10.1029/2019RG000660. PMC 7384191. PMID 32734279.
  46. ^ McNeill, V. Faye (2017). "Atmospheric Aerosols: Clouds, Chemistry, and Climate". Annual Review of Chemical and Biomolecular Engineering. 8 (1): 427–444. doi:10.1146/annurev-chembioeng-060816-101538. ISSN 1947-5438. PMID 28415861.
  47. ^ Samset, B. H.; Sand, M.; Smith, C. J.; Bauer, S. E.; Forster, P. M.; Fuglestvedt, J. S.; Osprey, S.; Schleussner, C.-F. (2018). "Climate Impacts From a Removal of Anthropogenic Aerosol Emissions". Geophysical Research Letters. 45 (2): 1020–1029. Bibcode:2018GeoRL..45.1020S. doi:10.1002/2017GL076079. ISSN 0094-8276. PMC 7427631. PMID 32801404.
  48. ^ IPCC AR5 WG1 Ch2 2013, p. 183.
  49. ^ He et al. 2018; Storelvmo et al. 2016
  50. ^ "Global 'Sunscreen' Has Likely Thinned, Report NASA Scientists". NASA. 15 March 2007. Archived from the original on 22 December 2018. Retrieved 13 March 2024.
  51. ^ "Aerosol pollution has caused decades of global dimming". American Geophysical Union. 18 February 2021. Archived from the original on 27 March 2023. Retrieved 18 December 2023.
  52. ^ Xia, Wenwen; Wang, Yong; Chen, Siyu; Huang, Jianping; Wang, Bin; Zhang, Guang J.; Zhang, Yue; Liu, Xiaohong; Ma, Jianmin; Gong, Peng; Jiang, Yiquan; Wu, Mingxuan; Xue, Jinkai; Wei, Linyi; Zhang, Tinghan (2022). "Double Trouble of Air Pollution by Anthropogenic Dust". Environmental Science & Technology. 56 (2): 761–769. Bibcode:2022EnST...56..761X. doi:10.1021/acs.est.1c04779. hdl:10138/341962. PMID 34941248. S2CID 245445736.
  53. ^ "Global Dimming Dilemma". 4 June 2020.
  54. ^ Wild et al. 2005; Storelvmo et al. 2016; Samset et al. 2018.
  55. ^ Twomey, S. (1977). "The Influence of Pollution on the Shortwave Albedo of Clouds". Journal of the Atmospheric Sciences. 34 (7): 1149–1152. Bibcode:1977JAtS...34.1149T. doi:10.1175/1520-0469(1977)034<1149:TIOPOT>2.0.CO;2. ISSN 0022-4928.[permanent dead link]
  56. ^ Albrecht 1989.
  57. ^ a b Fahey, D. W.; Doherty, S. J.; Hibbard, K. A.; Romanou, A.; Taylor, P. C. (2017). "Chapter 2: Physical Drivers of Climate Change" (PDF). National Climate Assessment.
  58. ^ Ramanathan & Carmichael 2008; RIVM 2016.
  59. ^ Sand, M.; Berntsen, T. K.; von Salzen, K.; Flanner, M. G.; Langner, J.; Victor, D. G. (2016). "Response of Arctic temperature to changes in emissions of short-lived climate forcers". Nature Climate Change. 6 (3): 286–289. Bibcode:2016NatCC...6..286S. doi:10.1038/nclimate2880. ISSN 1758-678X.
  60. ^ Butler, Rhett A. (31 March 2021). "Global forest loss increases in 2020". Mongabay. Archived from the original on 1 April 2021. ● Data from "Indicators of Forest Extent / Forest Loss". World Resources Institute. 4 April 2024. Archived from the original on 27 May 2024. Chart in section titled "Annual rates of global tree cover loss have risen since 2000".
  61. ^ Ritchie, Hannah; Roser, Max (16 February 2024). "Land Use". Our World in Data.
  62. ^ The Sustainability Consortium, 13 September 2018; UN FAO 2016, p. 18.
  63. ^ Solomon, S.; et al., "TS.2.1.1 Changes in Atmospheric Carbon Dioxide, Methane and Nitrous Oxide", Technical Summary, archived from the original on 15 October 2012, retrieved 18 August 2012, in IPCC AR4 WG1 2007.
  64. ^ Solomon, S.; et al., Technical Summary, archived from the original on 28 November 2018, retrieved 25 September 2011, in IPCC AR4 WG1 2007. [full citation needed]
  65. ^ IPCC (2019). "Summary for Policymakers" (PDF). Special Report on Climate Change and Land. pp. 3–34.
  66. ^ Curtis, Philip G.; Slay, Christy M.; Harris, Nancy L.; Tyukavina, Alexandra; Hansen, Matthew C. (14 September 2018). "Classifying drivers of global forest loss". Science. 361 (6407): 1108–1111. Bibcode:2018Sci...361.1108C. doi:10.1126/science.aau3445. ISSN 0036-8075. PMID 30213911.
  67. ^ a b Garrett, L.; Lévite, H.; Besacier, C.; Alekseeva, N.; Duchelle, M. (2022). The key role of forest and landscape restoration in climate action. Rome: FAO. doi:10.4060/cc2510en. ISBN 978-92-5-137044-5.
  68. ^ a b World Resources Institute, 8 December 2019
  69. ^ IPCC SRCCL Ch2 2019, p. 172: "The global biophysical cooling alone has been estimated by a larger range of climate models and is −0.10 ± 0.14 °C; it ranges from −0.57 °C to +0.06°C ... This cooling is essentially dominated by increases in surface albedo: historical land cover changes have generally led to a dominant brightening of land"
  70. ^ a b Steinfeld, Henning; Gerber, Pierre; Wassenaar, Tom; Castel, Vincent; Rosales, Mauricio; de Haan, Cees (2006). Livestock's Long Shadow (PDF). Food and Agricultural Organization of the U.N. ISBN 92-5-105571-8. Archived from the original (PDF) on 25 June 2008.
  71. ^ "CO2 is making Earth greener—for now". NASA. Archived from the original on 27 February 2020. Retrieved 28 February 2020.
  72. ^ IPCC SRCCL Summary for Policymakers 2019, p. 10
  73. ^ Climate.gov, 23 June 2022:"Carbon cycle experts estimate that natural "sinks"—processes that remove carbon from the atmosphere—on land and in the ocean absorbed the equivalent of about half of the carbon dioxide we emitted each year in the 2011–2020 decade."
  74. ^ IPCC AR6 WG1 Technical Summary 2021, p. TS-122, Box TS.5, Figure 1
  75. ^ Melillo et al. 2017: Our first-order estimate of a warming-induced loss of 190 Pg of soil carbon over the 21st century is equivalent to the past two decades of carbon emissions from fossil fuel burning.
  76. ^ IPCC SRCCL Ch2 2019, pp. 133, 144.
  77. ^ USGCRP Chapter 2 2017, pp. 93–95.
  78. ^ Liu, Y.; Moore, J. K.; Primeau, F.; Wang, W. L. (22 December 2022). "Reduced CO2 uptake and growing nutrient sequestration from slowing overturning circulation". Nature Climate Change. 13: 83–90. doi:10.1038/s41558-022-01555-7. OSTI 2242376. S2CID 255028552.
  79. ^ Pearce, Fred (18 April 2023). "New Research Sparks Concerns That Ocean Circulation Will Collapse". Retrieved 3 February 2024.
  80. ^ "Thermodynamics: Albedo". NSIDC. Archived from the original on 11 October 2017. Retrieved 10 October 2017.
  81. ^ "The study of Earth as an integrated system". Vitals Signs of the Planet. Earth Science Communications Team at NASA's Jet Propulsion Laboratory / California Institute of Technology. 2013. Archived from the original on 26 February 2019.
  82. ^ a b USGCRP Chapter 2 2017, pp. 89–91.
  83. ^ IPCC AR6 WG1 Technical Summary 2021, p. 58: The net effect of changes in clouds in response to global warming is to amplify human-induced warming, that is, the net cloud feedback is positive (high confidence)
  84. ^ USGCRP Chapter 2 2017, pp. 89–90.
  85. ^ IPCC AR5 WG1 2013, p. 14
  86. ^ IPCC AR6 WG1 Technical Summary 2021, pp. 58, 59: clouds remain the largest contribution to overall uncertainty in climate feedbacks
  87. ^ Wolff et al. 2015: "the nature and magnitude of these feedbacks are the principal cause of uncertainty in the response of Earth's climate (over multi-decadal and longer periods) to a particular emissions scenario or greenhouse gas concentration pathway."
  88. ^ Williams, Richard G; Ceppi, Paulo; Katavouta, Anna (2020). "Controls of the transient climate response to emissions by physical feedbacks, heat uptake and carbon cycling". Environmental Research Letters. 15 (9): 0940c1. Bibcode:2020ERL....15i40c1W. doi:10.1088/1748-9326/ab97c9. ISSN 1748-9326.
  89. ^ NASA, 28 May 2013.
  90. ^ Cohen, Judah; Screen, James A.; Furtado, Jason C.; Barlow, Mathew; Whittleston, David; Coumou, Dim; Francis, Jennifer; Dethloff, Klaus; Entekhabi, Dara; Overland, James; Jones, Justin (2014). "Recent Arctic amplification and extreme mid-latitude weather". Nature Geoscience. 7 (9): 627–637. Bibcode:2014NatGe...7..627C. doi:10.1038/ngeo2234. ISSN 1752-0894.
  91. ^ Turetsky et al. 2019
  92. ^ Dean et al. 2018.
  93. ^ IPCC AR6 WG1 Technical Summary 2021, p. 58: Feedback processes are expected to become more positive overall (more amplifying of global surface temperature changes) on multi-decadal time scales as the spatial pattern of surface warming evolves and global surface temperature increases.
  94. ^ "Climate Science Special Report: Fourth National Climate Assessment, Volume I - Chapter 3: Detection and Attribution of Climate Change". science2017.globalchange.gov. U.S. Global Change Research Program (USGCRP): 1–470. 2017. Archived from the original on 23 September 2019. Adapted directly from Fig. 3.3.
  95. ^ Wuebbles, D.J.; Fahey, D.W.; Hibbard, K.A.; Deangelo, B.; Doherty, S.; Hayhoe, K.; Horton, R.; Kossin, J.P.; Taylor, P.C.; Waple, A.M.; Yohe, C.P. (23 November 2018). "Climate Science Special Report / Fourth National Climate Assessment (NCA4), Volume I /Executive Summary / Highlights of the Findings of the U.S. Global Change Research Program Climate Science Special Report". globalchange.gov. U.S. Global Change Research Program: 1–470. doi:10.7930/J0DJ5CTG. Archived from the original on 14 June 2019.
  96. ^ IPCC (2001) Summary for Policymakers - A Report of Working Group I of the Intergovernmental Panel on Climate Change. In: TAR Climate Change 2001: The Scientific Basis
  97. ^ National Academies 2008, p. 6
  98. ^ "Is the Sun causing global warming?". Climate Change: Vital Signs of the Planet. Archived from the original on 5 May 2019. Retrieved 10 May 2019.
  99. ^ Fischer, Tobias P.; Aiuppa, Alessandro (2020). "AGU Centennial Grand Challenge: Volcanoes and Deep Carbon Global CO 2 Emissions From Subaerial Volcanism—Recent Progress and Future Challenges". Geochemistry, Geophysics, Geosystems. 21 (3). doi:10.1029/2019GC008690. ISSN 1525-2027.
  100. ^ USGCRP Chapter 2 2017, p. 79
  101. ^ IPCC, 2007: Summary for Policymakers. 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, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
  102. ^ Lockwood, Mike; Lockwood, Claus (2007). "Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature" (PDF). Proceedings of the Royal Society A. 463 (2086): 2447–2460. Bibcode:2007RSPSA.463.2447L. doi:10.1098/rspa.2007.1880. S2CID 14580351. Archived from the original (PDF) on 26 September 2007. Retrieved 21 July 2007.
  103. ^ USGCRP 2009, p. 20.
  104. ^ IPCC AR4 WG1 Ch9 2007, pp. 702–703; Randel et al. 2009.
  105. ^ Greicius, Tony (2 August 2022). "Tonga eruption blasted unprecedented amount of water into stratosphere". NASA Global Climate Change. Retrieved 18 January 2024. Massive volcanic eruptions like Krakatoa and Mount Pinatubo typically cool Earth's surface by ejecting gases, dust, and ash that reflect sunlight back into space. In contrast, the Tonga volcano didn't inject large amounts of aerosols into the stratosphere, and the huge amounts of water vapor from the eruption may have a small, temporary warming effect, since water vapor traps heat. The effect would dissipate when the extra water vapor cycles out of the stratosphere and would not be enough to noticeably exacerbate climate change effects.
  106. ^ USGCRP Chapter 2 2017, p. 79

Sources

IPCC reports

Fourth Assessment Report
Fifth Assessment report
Special Report: Climate change and Land
Sixth Assessment Report

Attribution