Editing Causes of climate change (section)

=== Aerosols ===
[[File:Bellouin_2019_aerosol_cloud_interactions.jpg|thumb|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.<ref name="Bellouin2019">{{Cite journal |last1=Bellouin |first1=N. |last2=Quaas |first2=J. |last3=Gryspeerdt |first3=E. |last4=Kinne |first4=S. |last5=Stier |first5=P. |last6=Watson-Parris |first6=D. |last7=Boucher |first7=O. |last8=Carslaw |first8=K. S. |last9=Christensen |first9=M. |last10=Daniau |first10=A.-L. |last11=Dufresne |first11=J.-L. |last12=Feingold |first12=G. |last13=Fiedler |first13=S. |last14=Forster |first14=P. |last15=Gettelman |first15=A. |last16=Haywood |first16=J. M. |last17=Lohmann |first17=U. |last18=Malavelle |first18=F. |last19=Mauritsen |first19=T. |last20=McCoy |first20= D. T. |last21=Myhre |first21=G. |last22=Mülmenstädt |first22=J. |last23=Neubauer |first23=D. |last24=Possner |first24=A. |last25=Rugenstein |first25=M. |last26=Sato |first26=Y. |last27=Schulz |first27=M. |last28=Schwartz |first28=S. E. |last29=Sourdeval |first29=O. |last30=Storelvmo |first30= T. |last31=Toll |first31=V. |last32=Winker |first32=D. |last33=Stevens |first33=B. |date=1 November 2019 |title=Bounding Global Aerosol Radiative Forcing of Climate Change |journal=Reviews of Geophysics |volume=58 |issue=1 |page=e2019RG000660 |doi=10.1029/2019RG000660 |pmid=32734279 |pmc=7384191 }}</ref> ]]
Air pollution, in the form of [[Particulates#Climate effects|aerosols, affects the climate]] on a large scale.<ref>{{Cite journal |last=McNeill |first=V. Faye |date=2017 |title=Atmospheric Aerosols: Clouds, Chemistry, and Climate |url=https://www.annualreviews.org/doi/10.1146/annurev-chembioeng-060816-101538 |journal=Annual Review of Chemical and Biomolecular Engineering |language=en |volume=8 |issue=1 |pages=427–444 |doi=10.1146/annurev-chembioeng-060816-101538 |pmid=28415861 |issn=1947-5438|doi-access=free }}</ref><ref>{{Cite journal |last1=Samset |first1=B. H. |last2=Sand |first2=M. |last3=Smith |first3=C. J. |last4=Bauer |first4=S. E. |last5=Forster |first5=P. M. |last6=Fuglestvedt |first6=J. S. |last7=Osprey |first7=S. |last8=Schleussner |first8=C.-F. |date=2018 |title=Climate Impacts From a Removal of Anthropogenic Aerosol Emissions |journal=Geophysical Research Letters |language=en |volume=45 |issue=2 |pages=1020–1029 |doi=10.1002/2017GL076079 |issn=0094-8276 |pmc=7427631 |pmid=32801404|bibcode=2018GeoRL..45.1020S }}</ref> Aerosols scatter and absorb solar radiation. From 1961 to 1990, a gradual reduction in the amount of [[irradiance|sunlight reaching the Earth's surface]] was observed. This phenomenon is popularly known as ''[[global dimming]]'',<ref>{{harvnb|IPCC AR5 WG1 Ch2|2013|p=183}}.</ref> and is primarily attributed to [[sulfate]] aerosols produced by the combustion of fossil fuels with heavy [[sulfur]] concentrations like [[coal]] and [[bunker fuel]].<ref name="Quaas2022" /> Smaller contributions come from [[black carbon]], organic carbon from combustion of fossil fuels and biofuels, and from anthropogenic dust.<ref>{{harvnb|He|Wang|Zhou|Wild|2018}}; {{Harvnb|Storelvmo|Phillips|Lohmann|Leirvik|2016}}</ref><ref name="NASA2007">{{cite news |date=15 March 2007 |title=Global 'Sunscreen' Has Likely Thinned, Report NASA Scientists |publisher=[[NASA]] |url=http://www.nasa.gov/centers/goddard/news/topstory/2007/aerosol_dimming.html |access-date=13 March 2024 |archive-date=22 December 2018 |archive-url=https://web.archive.org/web/20181222142212/https://www.nasa.gov/centers/goddard/news/topstory/2007/aerosol_dimming.html |url-status=dead }}</ref><ref>{{Cite web |date=18 February 2021 |title=Aerosol pollution has caused decades of global dimming |url=https://news.agu.org/press-release/aerosol-pollution-caused-decades-of-global-dimming/ |website=[[American Geophysical Union]] |access-date=18 December 2023 |archive-url=https://web.archive.org/web/20230327143716/https://news.agu.org/press-release/aerosol-pollution-caused-decades-of-global-dimming/ |archive-date=27 March 2023 }}</ref><ref>{{Cite journal |title=Double Trouble of Air Pollution by Anthropogenic Dust |year=2022 |doi=10.1021/acs.est.1c04779 |url=https://pubs.acs.org/doi/10.1021/acs.est.1c04779|last1=Xia |first1=Wenwen |last2=Wang |first2=Yong |last3=Chen |first3=Siyu |last4=Huang |first4=Jianping |last5=Wang |first5=Bin |last6=Zhang |first6=Guang J. |last7=Zhang |first7=Yue |last8=Liu |first8=Xiaohong |last9=Ma |first9=Jianmin |last10=Gong |first10=Peng |last11=Jiang |first11=Yiquan |last12=Wu |first12=Mingxuan |last13=Xue |first13=Jinkai |last14=Wei |first14=Linyi |last15=Zhang |first15=Tinghan |journal=Environmental Science & Technology |volume=56 |issue=2 |pages=761–769 |pmid=34941248 |bibcode=2022EnST...56..761X |hdl=10138/341962 |s2cid=245445736 |doi-access=free }}</ref><ref>{{Cite web |title=Global Dimming Dilemma |date=4 June 2020 |url=https://www.scientistswarning.org/2020/06/04/dimming-dilemma/}}</ref> Globally, aerosols have been declining since 1990 due to pollution controls, meaning that they no longer mask greenhouse gas warming as much.<ref>{{harvnb|Wild|Gilgen|Roesch|Ohmura|2005}}; {{Harvnb|Storelvmo|Phillips|Lohmann|Leirvik|2016}}; {{harvnb|Samset|Sand|Smith|Bauer|2018}}.</ref><ref name="Quaas2022" />

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.<ref>{{Cite journal |last=Twomey |first=S. |date=1977 |title=The Influence of Pollution on the Shortwave Albedo of Clouds |url=http://journals.ametsoc.org/doi/10.1175/1520-0469(1977)0342.0.CO;2 |journal=Journal of the Atmospheric Sciences |language=en |volume=34 |issue=7 |pages=1149–1152 |doi=10.1175/1520-0469(1977)034<1149:TIOPOT>2.0.CO;2 |bibcode=1977JAtS...34.1149T |issn=0022-4928 |doi-access=free }}{{Dead link|date=March 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> They also reduce the [[Cloud physics#Collision-coalescence|growth of raindrops]], which makes clouds more reflective to incoming sunlight.<ref>{{harvnb|Albrecht|1989}}.</ref> Indirect effects of aerosols are the largest uncertainty in [[radiative forcing]].<ref name="NCAR4_ch2">{{cite book  |first1=D. W. |last1=Fahey  |first2=S. J. |last2=Doherty |first3=K. A. |last3=Hibbard |first4=A. |last4=Romanou 
 |first5=P. C. |last5=Taylor |year=2017  |title=National Climate Assessment |chapter=Chapter 2: Physical Drivers of Climate Change |chapter-url=https://science2017.globalchange.gov/downloads/CSSR_Ch2_Physical_Drivers.pdf }}</ref>

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.<ref>{{harvnb|Ramanathan|Carmichael|2008}}; {{harvnb|RIVM|2016}}.</ref> Limiting new black carbon deposits in the Arctic could reduce global warming by 0.2&nbsp;°C by 2050.<ref>{{Cite journal |last1=Sand |first1=M. |last2=Berntsen |first2=T. K. |last3=von Salzen |first3=K. |last4=Flanner |first4=M. G. |last5=Langner |first5=J. |last6=Victor |first6=D. G. |date=2016 |title=Response of Arctic temperature to changes in emissions of short-lived climate forcers |url=https://www.nature.com/articles/nclimate2880 |journal=Nature Climate Change |language=en |volume=6 |issue=3 |pages=286–289 |doi=10.1038/nclimate2880 |bibcode=2016NatCC...6..286S |issn=1758-678X}}</ref>
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