Editing Ozone depletion (section)

== Misconceptions ==

=== CFC weight ===
Since CFC molecules are heavier than air (nitrogen or oxygen), it is commonly believed that the CFC molecules cannot reach the stratosphere in significant amounts.<ref>{{cite news |author=Silverman, Amy |url=http://www.phoenixnewtimes.com/1995-05-04/news/freon-easy/full |title=Freon Easy |publisher=Phoenix News |date=May 4, 1995 |access-date=April 6, 2011 |archive-date=October 11, 2007 |archive-url=https://web.archive.org/web/20071011180256/http://phoenixnewtimes.com/1995-05-04/news/freon-easy/full |url-status=dead }}</ref> However, atmospheric gases are not sorted by weight at these altitudes; the forces of wind can fully mix the gases in the atmosphere. Some of the heavier CFCs are not evenly distributed.<ref>{{cite journal|title=The vertical distribution of CFC-114 (CClF2-CClF2) in the atmosphere|doi=10.1029/JD090iD07p13091|bibcode=1985JGR....9013091F|volume=90|issue = D7|journal=Journal of Geophysical Research|pages=13091|year=1985|last1=Fabian|first1=P.|last2=Borchers|first2=R.|last3=Krüger|first3=B. C.|last4=Lal|first4=S.}}</ref>

=== Percentage of human-made chlorine ===
[[File:Sources stratospheric chlorine.png|right|thumb|upright=1.7|Sources of stratospheric chlorine]]

Another misconception is that natural sources of chlorine are several times larger than human-made ones. While this statement is true for tropospheric chlorine, that is irrelevant to ozone depletion, which is only affected by stratospheric chlorine. Chlorine from [[salt spray|ocean spray]] is soluble and thus is washed by rainfall before it reaches the stratosphere. CFCs, in contrast, are insoluble and long-lived, allowing them to reach the stratosphere. In the lower atmosphere, there is much more chlorine from CFCs and related [[haloalkane]]s than there is in HCl from salt spray, and in the stratosphere halocarbons are dominant.<ref>[http://www.faqs.org/faqs/ozone-depletion/stratcl ozone-depletion FAQ, Part II] {{Webarchive|url=https://web.archive.org/web/20090203032254/http://www.faqs.org/faqs/ozone-depletion/stratcl/ |date=2009-02-03 }}, section 4.3</ref> Only methyl chloride, which is one of these halocarbons, has a mainly natural source,<ref>{{Cite journal
| last1 = Yokouchi | first1 = Y.
| last2 = Noijiri | first2 = Y.
| last3 = Barrie | first3 = L. A.
| last4 = Toom-Sauntry | first4 = D.
| last5 = Machida | first5 = T.
| last6 = Inuzuka | first6 = Y.
| last7 = Akimoto | first7 = H.
| last8 = Li | first8 = H. -J.
| last9 = Fujinuma | first9 = Y.
| last10 = Aoki | first10 = S.
| title = A strong source of methyl chloride to the atmosphere from tropical coastal land
| journal = Nature
| volume = 403
| issue = 6767
| pages = 295–298
| doi = 10.1038/35002049
| year = 2000
| pmid = 10659845
| bibcode = 2000Natur.403..295Y
| s2cid = 4318352
}}</ref> and it is responsible for about 20 percent of the chlorine in the stratosphere; the remaining 80 percent comes from human-made sources.

Very violent volcanic eruptions can inject HCl into the stratosphere, but researchers have shown that the contribution is not significant compared to that from CFCs.<ref name="O3F4_4">[http://www.faqs.org/faqs/ozone-depletion/stratcl ozone-depletion FAQ, Part II] {{Webarchive|url=https://web.archive.org/web/20090203032254/http://www.faqs.org/faqs/ozone-depletion/stratcl/ |date=2009-02-03 }}, section 4.4</ref> A similar erroneous assertion is that soluble halogen compounds from the volcanic plume of [[Mount Erebus]] on Ross Island, Antarctica are a major contributor to the Antarctic ozone hole.<ref name="O3F4_4" />

Nevertheless, a 2015 study showed that the role of [[Mount Erebus]] volcano in the Antarctic ozone depletion was probably underestimated. Based on the [[NCEP/NCAR reanalysis]] data over the last 35 years and by using the NOAA [[HYSPLIT]] trajectory model, researchers showed that gas emissions from the volcano (including [[hydrogen chloride]] (HCl)) can reach the Antarctic stratosphere via high-latitude cyclones and then the [[polar vortex]]. Depending on the level of its volcanic activity, the additional annual HCl mass entering the stratosphere from Erebus varies from 1.0 to 14.3 kt.<ref>{{cite journal |last1=Zuev |first1=V. V. |last2=Zueva |first2=N. E. |last3=Savelieva |first3=E. S. |last4=Gerasimov |first4=V. V. |year=2015 |title=The Antarctic ozone depletion caused by Erebus volcano gas emissions |journal=[[Atmospheric Environment]] |volume=122 |pages=393–399 |bibcode=2015AtmEn.122..393Z |doi=10.1016/j.atmosenv.2015.10.005 |doi-access=free}}</ref>

=== First observation ===
[[G.M.B. Dobson]] mentioned that when springtime ozone levels in the Antarctic over [[Halley Research Station|Halley Bay]] were first measured in 1956, he was surprised to find that they were only about 320 DU, about 150 DU below typical spring Arctic levels of around 450 DU. What Dobson observed was not an ozone hole but in fact a typical annual maximum Antarctic ozone concentration: actual ozone hole values are in the 150–100 DU range.<ref>[[G.M.B. Dobson|Dobson, G.M.B.]] (1968) ''Exploring the Atmosphere'', 2nd Edition, Oxford University Press.</ref> While Arctic ozone concentrations vary on a smooth annual cycle from around 300 to 450 DU, peaking in the northern hemisphere spring, Antarctic concentrations drop sharply in the southern hemisphere spring from highs of around 300 DU to much lower values. Peak values are not reached again until December.<ref>[http://www.faqs.org/faqs/ozone-depletion/antarctic ozone-depletion FAQ, Part III] {{Webarchive|url=https://web.archive.org/web/20090224015731/http://www.faqs.org/faqs/ozone-depletion/antarctic/ |date=2009-02-24 }}, section 6. faqs.org</ref>

=== Location of hole ===
Some people thought that the ozone hole should be above the sources of CFCs. However, CFCs are well mixed globally in the [[troposphere]] and [[stratosphere]]. The reason for occurrence of the ozone hole above Antarctica is not because there are more CFCs concentrated but because the low temperatures help form polar stratospheric clouds.<ref>{{cite web|url=http://www.faqs.org/faqs/ozone-depletion/antarctic |title=ozone-depletion FAQ, Antarctic |publisher=Faqs.org |access-date=April 6, 2011}}</ref> In fact, there are findings of significant and localized "ozone holes" above other parts of the Earth, such as above Central Asia.<ref>{{Citation |last1=Chen |first1=Sheng Bo |title=Stratospheric ozone change over the Tibetan Plateau |journal=Atmospheric Pollution Research |volume=8 |issue=3 |pages=528–534 |year=2017 |bibcode=2017AtmPR...8..528C |doi=10.1016/j.apr.2016.11.007 |last2=Zhao |first2=Liang |last3=Tao |first3=Yu Long}}</ref>

=== Awareness campaigns ===
Public misconceptions and misunderstandings of complex issues like ozone depletion are common. The limited scientific knowledge of the public led to confusion about global warming<ref>{{cite journal | last1 = Boyesa | first1 = Edward | last2 = Stanisstreeta | first2 = Martin | year = 1992 | title = Students' perceptions of global warming | journal = International Journal of Environmental Studies | volume = 42 | issue = 4| pages = 287–300 | doi = 10.1080/00207239208710804 | bibcode = 1992IJEnS..42..287B }}</ref> or the perception of global warming as a subset of the "ozone hole".<ref>Compare Sheldon Ungar, 2000 and various web sites such as [[Gavin Schmidt]]'s realclimate complaint in [http://www.realclimate.org/index.php/archives/2005/04/ozone-depletion-and-global-warming/ Ozone depletion and global warming 2005] {{Webarchive|url=https://web.archive.org/web/20141010155135/http://www.realclimate.org/index.php/archives/2005/04/ozone-depletion-and-global-warming/ |date=2014-10-10 }} or the [http://www.ucsusa.org/global_warming/science_and_impacts/science/ozone-hole-and-gw-faq.html UCS FAQ on the topic]</ref> In the beginning, classical green NGOs refrained from using CFC depletion for campaigning, as they assumed the topic was too complicated.<ref name = RG /> They became active much later, e.g. in Greenpeace's support for a CFC-free refrigerator produced by the former East German company [[Volkseigener Betrieb|VEB]] dkk Scharfenstein.<ref name = RG /><ref name=Spiegel>{{Cite news |title=Öko-Coup aus Ostdeutschland |url=http://www.spiegel.de/einestages/oeko-revolution-aus-ostdeutschland-wie-foron-den-ersten-fckw-freien-kuehlschrank-der-welt-erfand-a-951064.html|date=September 13, 2013 |work=[[Der Spiegel]] |language=de |access-date=4 September 2015|last1=Gunkel|first1=Christoph}}</ref>

The metaphors used in the CFC discussion (ozone shield, ozone hole) are not "exact" in the scientific sense. The "ozone hole" is more of a ''depression'', less "a hole in the windshield". The ozone does not disappear through the layer, nor is there a uniform "thinning" of the ozone layer. However, they resonated better with non-scientists and their concerns.<ref name = Ungar /> The ozone hole was seen as a "hot issue" and imminent risk<ref name="PAR">{{cite journal | date=14 May 2007 | first1=Reiner | journal=Environmental Politics | issue=3 | last1=Grundmann | url=http://stsclimate.soc.ku.dk/papers/grundmannclimatechangeandknowledgepolitics.pdf | title=Climate Change and Knowledge Politics | volume=16 | pages=414–432 | doi=10.1080/09644010701251656 | bibcode=2007EnvPo..16..414G | url-status=dead | archive-url=https://web.archive.org/web/20140826115142/http://stsclimate.soc.ku.dk/papers/grundmannclimatechangeandknowledgepolitics.pdf | archive-date=August 26, 2014 | df=mdy-all | citeseerx=10.1.1.535.4984 | s2cid=153866225 }}</ref> as laypeople feared severe personal consequences such as skin cancer, cataracts, damage to plants, and reduction of plankton populations in the ocean's photic zone. Not only on the policy level, [[Ozone depletion and climate change|ozone regulation compared to climate change]] fared much better in public opinion. Americans voluntarily switched away from aerosol sprays before legislation was enforced, while climate change failed to achieve comparable concern and public action.<ref name = Ungar /> The sudden identification in 1985 that there was a substantial "hole" was widely reported in the press. The especially rapid ozone depletion in Antarctica had previously been dismissed as a measurement error.<ref name="Zehr94" /> Scientific consensus was established after regulation.<ref name = RG />

While the Antarctic ozone hole has a relatively small effect on global ozone, the hole has generated a great deal of public interest because:
* Many have worried that ozone holes might start appearing over other areas of the globe, though to date the only other large-scale depletion is a smaller ozone "dimple" observed during the Arctic spring around the North Pole. Ozone at middle latitudes has declined, but by a much smaller extent (a decrease of about 4–5 percent).
* If stratospheric conditions become more severe (cooler temperatures, more clouds, more active chlorine), global ozone may decrease at a greater pace. Standard [[global warming]] theory predicts that the stratosphere will cool.<ref>{{cite web |url=http://www.grida.no/publications/other/ipcc%5Ftar/?src=/climate/ipcc_tar/wg1/351.htm |title=Climate Change 2001: Working Group I: The Scientific Basis |pages=Chapter 9.3.2 Patterns of Future Climate Change |year=2001 |work=[[Intergovernmental Panel on Climate Change]] Work Group I |access-date=May 28, 2016 |url-status=dead |archive-url=https://web.archive.org/web/20160603033745/http://www.grida.no/publications/other/ipcc_tar/?src=%2Fclimate%2Fipcc_tar%2Fwg1%2F351.htm |archive-date=June 3, 2016 |df=mdy-all }}</ref>
* When the Antarctic ozone hole breaks up each year, the ozone-depleted air drifts into nearby regions. Decreases in the ozone level of up to 10 percent have been reported in New Zealand in the month following the breakup of the Antarctic ozone hole,<ref>{{cite web |last=Muir |first=Patricia |url=http://people.oregonstate.edu/~muirp/stratozo.htm |title=Stratospheric Ozone Depletion |publisher=Oregon State University |date=March 6, 2008 |access-date=April 16, 2011}}</ref> with ultraviolet-B radiation intensities increasing by more than 15 percent since the 1970s.<ref>{{cite web|title=Long-term increase in summer UV radiation|url=http://www.niwa.co.nz/news/long-term-increase-summer-uv-radiation|publisher=NIWA|access-date=December 4, 2013|date=1999-09-09}}</ref><ref>{{cite journal|last1=McKenzie|first1=Richard|last2=Conner|first2=Brian|last3=Bodeker|first3=Greg|title=Increased Summertime UV Radiation in New Zealand in Response to Ozone Loss|journal=Science|date=September 10, 1999|volume=285|issue=5434|pages=1709–1711|doi=10.1126/science.285.5434.1709|pmid=10481002}}</ref>