Editing Climate variability and change (section)

==== Other mechanisms ====
It has been postulated that [[ion]]ized particles known as [[cosmic ray]]s could impact cloud cover and thereby the climate. As the sun shields the Earth from these particles, changes in solar activity were hypothesized to influence climate indirectly as well. To test the hypothesis, [[CERN]] designed the [[CLOUD experiment]], which showed the effect of cosmic rays is too weak to influence climate noticeably.<ref>{{Cite web|url=https://www.carbonbrief.org/why-the-sun-is-not-responsible-for-recent-climate-change|title=Explainer: Why the sun is not responsible for recent climate change|last=Hausfather|first=Zeke|date=18 August 2017|website=Carbon Brief|access-date=5 September 2019|archive-date=17 March 2023|archive-url=https://web.archive.org/web/20230317140828/https://www.carbonbrief.org/why-the-sun-is-not-responsible-for-recent-climate-change/|url-status=live}}</ref><ref>{{Cite journal|last=Pierce|first=J. R.|date=2017|title=Cosmic rays, aerosols, clouds, and climate: Recent findings from the CLOUD experiment|journal=Journal of Geophysical Research: Atmospheres|volume=122|issue=15|pages=8051–55|doi=10.1002/2017JD027475|bibcode=2017JGRD..122.8051P|s2cid=125580175 |issn=2169-8996}}</ref>

Evidence exists that the [[Chicxulub crater|Chicxulub asteroid impact]] some 66 million years ago had severely affected the Earth's climate. Large quantities of sulfate aerosols were kicked up into the atmosphere, decreasing global temperatures by up to 26&nbsp;°C and producing sub-freezing temperatures for a period of 3–16 years. The recovery time for this event took more than 30 years.<ref name="Brugger-2017">{{citation
 | contribution=Severe environmental effects of Chicxulub impact imply key role in end-Cretaceous mass extinction
 | last1=Brugger | first1=Julia
 | last2=Feulner | first2=Georg | last3=Petri | first3=Stefan
 | title=19th EGU General Assembly, EGU2017, proceedings from the conference, 23–28 April 2017|location=Vienna, Austria
 | volume=19 | pages=17167 | date=April 2017 | bibcode=2017EGUGA..1917167B | postscript=. }}</ref> The large-scale use of [[nuclear weapon]]s has also been investigated for its impact on the climate. The hypothesis is that soot released by large-scale fires blocks a significant fraction of sunlight for as much as a year, leading to a sharp drop in temperatures for a few years. This possible event is described as [[nuclear winter]].{{sfn|Burroughs|2001|p=232}}

[[Land surface effects on climate|Humans' use of land]] impact how much sunlight the surface reflects and the concentration of dust. Cloud formation is not only influenced by how much water is in the air and the temperature, but also by the amount of [[aerosols]] in the air such as dust.<ref>{{Cite web|url=https://www.chemistryworld.com/news/mineral-dust-plays-key-role-in-cloud-formation-and-chemistry/6157.article|title=Mineral dust plays key role in cloud formation and chemistry|last=Hadlington|first=Simon 9|date=May 2013|website=Chemistry World|access-date=5 September 2019|archive-date=24 October 2022|archive-url=https://web.archive.org/web/20221024053651/https://www.chemistryworld.com/news/mineral-dust-plays-key-role-in-cloud-formation-and-chemistry/6157.article|url-status=live}}</ref> Globally, more dust is available if there are many regions with dry soils, little vegetation and strong winds.<ref>{{Cite journal|last1=Mahowald|first1=Natalie|author-link=Natalie Mahowald|last2=Albani|first2=Samuel|last3=Kok|first3=Jasper F.|last4=Engelstaeder|first4=Sebastian|last5=Scanza|first5=Rachel|last6=Ward|first6=Daniel S.|last7=Flanner|first7=Mark G.|date=1 December 2014|title=The size distribution of desert dust aerosols and its impact on the Earth system|journal=Aeolian Research|volume=15|pages=53–71|bibcode=2014AeoRe..15...53M|doi=10.1016/j.aeolia.2013.09.002|issn=1875-9637|doi-access=free}}</ref>