Editing Ozone depletion (section)

=== Arctic ozone "mini-hole" ===
On March 3, 2005, the journal ''Nature''<ref>{{Cite journal|url=http://www.nature.com/news/2005/050228/full/news050228-12.html|title=Solar wind hammers the ozone layer|journal=Nature|access-date=May 28, 2016|doi=10.1038/news050228-12|year=2005|last1=Schiermeier|first1=Quirin|pages=news050228–12}}</ref> published an article linking 2004's unusually large Arctic ozone hole to solar wind activity.

On March 15, 2011, a record ozone layer loss was observed, with about half of the ozone present over the Arctic having been destroyed.<ref>{{cite magazine |author=Dell'Amore, Christine |url=http://news.nationalgeographic.com/news/2011/03/110321-ozone-layer-hole-arctic-north-pole-science-environment-uv-sunscreen/ |archive-url=https://web.archive.org/web/20110324184811/http://news.nationalgeographic.com/news/2011/03/110321-ozone-layer-hole-arctic-north-pole-science-environment-uv-sunscreen/ |url-status=dead |archive-date=March 24, 2011 |title=First North Pole Ozone Hole Forming? |magazine=National Geographic |date=March 22, 2011 |access-date=April 6, 2011}}</ref><ref name=verge/><ref>{{cite web|url=http://scienceblogs.com/deanscorner/2011/03/the_arctic_ozone_sieve_more_gl.php |title=The Arctic Ozone Sieve: More Global Weirding? |publisher=Scienceblogs.com |date=March 25, 2011 |access-date=April 6, 2011 |url-status=unfit |archive-url=https://web.archive.org/web/20110404141912/http://scienceblogs.com/deanscorner/2011/03/the_arctic_ozone_sieve_more_gl.php |archive-date=April 4, 2011 }}</ref> The change was attributed to increasingly cold winters in the Arctic stratosphere at an altitude of approximately {{convert|20|km|mi|abbr=on}}, a change associated with global warming in a relationship that is still under investigation.<ref name=verge>{{cite web|url=https://www.sciencedaily.com/releases/2011/03/110314100835.htm |title=Arctic on the verge of record ozone loss |author=Helmholtz Association of German Research Centres |website=Science Daily |date=March 14, 2011 |access-date=April 6, 2011}}</ref> By March 25, the ozone loss had become the largest compared to that observed in all previous winters with the possibility that it would become an ozone hole.<ref name="euractiv1">{{cite web|url=http://www.euractiv.com/en/climate-environment/developing-ozone-hole-approaches-europe-news-503504 |title=Developing ozone hole approaches Europe |publisher=EurActiv |access-date=April 6, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110404023940/http://www.euractiv.com/en/climate-environment/developing-ozone-hole-approaches-europe-news-503504 |archive-date=April 4, 2011 }}</ref> This would require that the quantities of ozone to fall below 200 Dobson units, from the 250 recorded over central Siberia.<ref name="euractiv1" /> It is predicted that the thinning layer would affect parts of Scandinavia and Eastern Europe on March 30–31.<ref name="euractiv1" />

On October 2, 2011, a study was published in the journal ''[[Nature (journal)|Nature]]'', which said that between December 2010 and March 2011 up to 80 percent of the ozone in the atmosphere at about {{convert|20|km|mi}} above the surface was destroyed.<ref name="bbc">{{cite news|title=Arctic ozone loss at record level|url=https://www.bbc.co.uk/news/science-environment-15105747|work=[[BBC News]] Online|access-date=October 3, 2011|archive-url=https://web.archive.org/web/20111002225339/http://www.bbc.co.uk/news/science-environment-15105747|archive-date=October 2, 2011|url-status=live|date=October 2, 2011}}</ref> The level of ozone depletion was severe enough that scientists said it could be compared to the ozone hole that forms over Antarctica every winter.<ref name="bbc" /> According to the study, "for the first time, sufficient loss occurred to reasonably be described as an Arctic ozone hole."<ref name="bbc" /> The study analyzed data from the [[Aura (satellite)|Aura]] and [[CALIPSO]] satellites, and determined that the larger-than-normal ozone loss was due to an unusually long period of cold weather in the Arctic, some 30 days more than typical, which allowed for more ozone-destroying chlorine compounds to be created.<ref name="press release" /> According to Lamont Poole, a co-author of the study, cloud and aerosol particles on which the chlorine compounds are found "were abundant in the Arctic until mid March 2011—much later than usual—with average amounts at some altitudes similar to those observed in the Antarctic, and dramatically larger than the near-zero values seen in March in most Arctic winters".<ref name="press release">{{cite press release |title=Unprecedented Arctic Ozone Loss in 2011, Says NASA-Led Study |url=http://www.nasa.gov/centers/langley/news/releases/2011/11-085.html |publisher=NASA |access-date=July 1, 2016 |date=October 2, 2011 |archive-date=July 9, 2023 |archive-url=https://web.archive.org/web/20230709105936/https://www.nasa.gov/centers/langley/news/releases/2011/11-085.html |url-status=dead }}</ref>

In 2013, researchers analyzed the data and found the 2010–2011 Arctic event did not reach the ozone depletion levels to classify as a true hole. A hole in the ozone is generally classified as 220 Dobson units or lower;<ref>{{Cite journal|last1=Millan|first1=Luis|last2=Manney|first2=Gloria|date=2017-05-02|title=An assessment of Ozone Mini-holes Representation in Reanalyses Over the Northern Hemisphere|url=https://www.researchgate.net/publication/316632591|journal=Atmospheric Chemistry and Physics Discussions|volume=17|issue=15|page=9277|doi=10.5194/acp-2017-341|bibcode=2017ACP....17.9277M |doi-access=free }}</ref> the Arctic hole did not approach that low level.<ref>{{Cite journal|last1=Strahan|first1=S. E.|last2=Douglass|first2=A. R.|last3=Newman|first3=P. A.|date=2013|title=The contributions of chemistry and transport to low arctic ozone in March 2011 derived from Aura MLS observations|journal=Journal of Geophysical Research: Atmospheres|language=en|volume=118|issue=3|pages=1563–1576|doi=10.1002/jgrd.50181|bibcode=2013JGRD..118.1563S|issn=2169-8996|hdl=2060/20120011691|s2cid=128447261|hdl-access=free}}</ref><ref>{{Cite web|url=http://www.nasa.gov/topics/earth/features/2011-ozone-hole.html|title=NASA Pinpoints Causes of 2011 Arctic Ozone Hole|last=Zell|first=Holly|date=2013-06-07|website=NASA|language=en|access-date=2019-10-03|archive-date=2019-09-07|archive-url=https://web.archive.org/web/20190907014502/https://www.nasa.gov/topics/earth/features/2011-ozone-hole.html|url-status=dead}}</ref> It has since been classified as a "mini-hole."<ref>{{Cite web|url=https://www.livescience.com/27824-arctic-ozone-loss-nasa.html|title=Cause of Odd Arctic Ozone 'Hole' Found|last=Earth|first=Stephanie Pappas 2013-03-11T23:38:39Z Planet|website=livescience.com|date=11 March 2013|language=en|access-date=2019-10-03}}</ref>

Following the ozone depletion in 1997 and 2011, a 90% drop in ozone was measured by [[weather balloons]] over the Arctic in March 2020, as they normally recorded 3.5 parts per million of ozone, compared to only around 0.3 parts per million lastly, due to the coldest temperatures ever recorded since 1979, and a strong polar [[vortex]] which allowed chemicals, including chlorine and bromine, to reduce ozone.<ref>{{cite journal|url=https://www.nature.com/articles/d41586-020-00904-w|title=Rare ozone hole opens over Arctic — and it's big|journal=Nature|date=27 March 2020|doi=10.1038/d41586-020-00904-w|last1=Witze|first1=Alexandra|volume=580|issue=7801|pages=18–19|pmid=32221510|bibcode=2020Natur.580...18W|s2cid=214694393}}</ref>

A rare hole, the result of unusually low temperatures in the atmosphere above the North Pole, was studied in 2020.<ref>{{Cite news |last=Harvey |first=Fiona |author-link=Fiona Harvey |date=2020-04-07 |title=Record-size hole opens in ozone layer above the Arctic |url=https://www.theguardian.com/environment/2020/apr/07/record-size-hole-opens-in-ozone-layer-above-the-arctic |access-date=2020-04-08 |work=[[The Guardian]] |language=en-GB |issn=0261-3077}}</ref><ref>{{cite news |last1=Lubben |first1=Alex |title=Now There's Another Hole in the Ozone Layer. Great. |url=https://www.vice.com/en/article/now-theres-another-hole-in-the-ozone-layer-great/ |work=[[Vice (magazine)|Vice]]|date=8 April 2020 |language=en}}</ref>