Editing Ozone depletion (section)

== Ozone depletion and global warming ==
{{main|Ozone depletion and climate change}}
Among others, [[Robert Watson (scientist)|Robert Watson]] had a role in the science assessment and in the regulation efforts of [[Ozone depletion and climate change|ozone depletion and global warming]].<ref name="RG">[[Reiner Grundmann]] [http://www.mpifg.de/pu/mpifg_book/mpifg_bd_39.pdf ''Technische Problemlösung, Verhandeln und umfassende Problemlösun''g, generic problem solving capability)] {{Webarchive|url=https://web.archive.org/web/20160303233113/http://www.mpifg.de/pu/mpifg_book/mpifg_bd_39.pdf|date=2016-03-03}} in Gesellschaftliche Komplexität und kollektive Handlungsfähigkeit (Societys complexity and collective ability to act), ed. Schimank, U. (2000). Frankfurt/Main, Germany: Campus, pp. 154–182, [http://pubman.mpdl.mpg.de/pubman/faces/viewItemFullPage.jsp;jsessionid=1F12495443EF6AC95BFF12F29F3C4829?itemId=escidoc%3A1235032%3A2&view=EXPORT book summary at the Max Planck Gesellschaft] {{Webarchive|url=https://web.archive.org/web/20141012202222/http://pubman.mpdl.mpg.de/pubman/faces/viewItemFullPage.jsp;jsessionid=1F12495443EF6AC95BFF12F29F3C4829?itemId=escidoc%3A1235032%3A2&view=EXPORT|date=2014-10-12}}.</ref> Prior to the 1980s, the EU, NASA, NAS, UNEP, WMO and the British government had dissenting scientific reports and Watson played a role in the process of unified assessments. Based on the experience with the ozone case, the IPCC started to work on a unified reporting and science assessment<ref name = RG /> to reach a consensus to provide the [[IPCC Summary for Policymakers]].

There are various areas of linkage between ozone depletion and global warming science:

[[File:Radiative-forcings.svg|thumb|upright=1.7|[[Radiative forcing]] from various greenhouse gases and other sources]]
* The same {{chem|CO|2}} radiative forcing that produces global warming is expected to cool the stratosphere.<ref name="ipcc2007">{{cite web | url=http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter9.pdf | title=Understanding and Attributing Climate Change | work=Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change | access-date=February 1, 2008 | publisher=[[Intergovernmental Panel on Climate Change]] | last=Hegerl | first=Gabriele C. | page=675 | display-authors=etal | archive-date=May 8, 2018 | archive-url=https://web.archive.org/web/20180508152907/http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter9.pdf | url-status=dead }}</ref> This cooling, in turn, is expected to produce a relative ''increase'' in ozone ({{chem|O|3}}) depletion in polar areas and the frequency of ozone holes.<ref>{{cite web|title=Ozone Depletion|url=http://earthwatch.unep.net/emergingissues/atmosphere/ozonedepletion.php|archive-url=https://web.archive.org/web/20100116051422/http://earthwatch.unep.net/emergingissues/atmosphere/ozonedepletion.php|url-status=dead|archive-date=16 January 2010|publisher=UNEP/DEWA/Earthwatch|date=16 January 2010}}</ref>
* Conversely, ozone depletion represents a radiative forcing of the climate system. There are two opposing effects: Reduced ozone causes the stratosphere to absorb less solar radiation, thus cooling the stratosphere while warming the troposphere; the resulting colder stratosphere emits less long-wave radiation downward, thus cooling the troposphere. Overall, the cooling dominates; the IPCC concludes "''observed stratospheric [[Ozone|{{chem|O|3}}]] losses over the past two decades have caused a negative forcing of the surface-troposphere system''"<ref name="wg1_223">{{cite web |url=http://www.grida.no/climate/ipcc_tar/wg1/223.htm |title=Climate Change 2001: Working Group I: The Scientific Basis |pages=Chapter 6.4 Stratospheric Ozone |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/20160603033740/http://www.grida.no/climate/ipcc_tar/wg1/223.htm |archive-date=June 3, 2016 |df=mdy-all }}</ref> of about −0.15&nbsp;± 0.10 [[watt]]s per square meter (W/m<sup>2</sup>).<ref name="spm_ozone"/>
* One of the strongest predictions of the greenhouse effect is that the stratosphere will cool.<ref name="ipcc2007" /> Although this cooling has been observed, it is not trivial to separate the effects of changes in the concentration of greenhouse gases and ozone depletion since both will lead to cooling. However, this can be done by numerical stratospheric modeling. Results from the [[National Oceanic and Atmospheric Administration]]'s [[Geophysical Fluid Dynamics Laboratory]] show that above {{convert|20|km|mi|abbr=on}}, the greenhouse gases dominate the cooling.<ref>{{cite web|title=The Relative Roles of Ozone and Other Greenhouse Gases in Climate Change in the Stratosphere |publisher=Geophysical Fluid Dynamics Laboratory |url=http://www.gfdl.noaa.gov/aboutus/milestones/ozone.html |date=February 29, 2004 |access-date=March 13, 2015 |url-status=unfit |archive-url=https://web.archive.org/web/20090120195248/http://www.gfdl.noaa.gov/aboutus/milestones/ozone.html |archive-date=January 20, 2009 }}</ref>
* Ozone depleting chemicals are also often greenhouse gases. The increases in concentrations of these chemicals have produced 0.34&nbsp;± 0.03&nbsp;W/m<sup>2</sup> of radiative forcing, corresponding to about 14 percent of the total radiative forcing from increases in the concentrations of well-mixed greenhouse gases.<ref name="spm_ozone" />
* The long term modeling of the process, its measurement, study, design of theories and testing take decades to document, gain wide acceptance, and ultimately become the dominant paradigm. Several theories about the destruction of ozone were hypothesized in the 1980s, published in the late 1990s, and are now being investigated. Dr Drew Schindell, and Dr Paul Newman, NASA Goddard, proposed a theory in the late 1990s, using computational modeling methods to model ozone destruction, that accounted for 78 percent of the ozone destroyed. Further refinement of that model accounted for 89 percent of the ozone destroyed, but pushed back the estimated recovery of the ozone hole from 75 years to 150 years. (An important part of that model is the lack of stratospheric flight due to depletion of [[fossil fuels]].)

In 2019, NASA reported that there was no significant relation between size of the ozone hole and climate change.<ref name="nasa2019"/>