Editing IPCC Third Assessment Report (section)

{{short description|Assessment of available scientific and socio-economic information on climate change by the IPCC}}
[[File:John Houghton High Wycombe 20050226.jpg|thumb|right|IPCC WG1 co-chair Sir [[John T. Houghton]] showing the IPCC fig. 2.20 [[hockey stick graph (global temperature)|hockey stick graph]] at a climate conference in 2005]]
The '''IPCC Third Assessment Report''' ('''TAR'''), ''Climate Change 2001'', is an assessment of available scientific and socio-economic information on climate change by the [[IPCC]]. Statements of the IPCC or information from the TAR were often used as a reference showing a [[scientific opinion on climate change|scientific consensus]] on the subject of [[global warming]]. The Third Assessment Report (TAR) was completed in 2001 and consists of four reports, three of them from its Working Groups: Working Group I: The Scientific Basis;<ref name="IPCC WG1">[https://www.ipcc.ch/report/ar3/wg1/ TAR Working Group 1] {{Webarchive|url=https://web.archive.org/web/20211228165314/https://www.ipcc.ch/report/ar3/wg1/ |date=2021-12-28 }}, IPCC.</ref> Working Group II: Impacts, Adaptation and Vulnerability;<ref name="IPCC WG2">[https://www.ipcc.ch/report/ar3/wg2/ TAR Working Group 2] {{Webarchive|url=https://web.archive.org/web/20160514070847/http://www.grida.no/publications/other/ipcc_tar/?src=%2Fclimate%2Fipcc_tar%2Fwg2%2Findex.htm |date=2016-05-14 }}, IPCC.</ref> Working Group III: Mitigation;<ref name="IPCC WG3">[https://www.ipcc.ch/report/ar3/wg3/ TAR Working Group 3] {{Webarchive|url=https://web.archive.org/web/20170227094845/http://www.grida.no/publications/other/ipcc_tar/?src=%2Fclimate%2Fipcc_tar%2Fwg3%2Findex.htm |date=2017-02-27 }}, IPCC.</ref> Synthesis Report.<ref name="IPCC Synth">[https://www.ipcc.ch/report/ar3/syr/ TAR Synthesis Report] {{Webarchive|url=https://web.archive.org/web/20210814135724/https://www.ipcc.ch/report/ar3/syr/ |date=2021-08-14 }}, IPCC.</ref> A number of the TAR's conclusions are given quantitative estimates of how probable it is that they are correct, e.g., greater than 66% probability of being correct.<ref name="tar uncertainties">{{citation|title=Box 2-1: Confidence and likelihood statements|df=dmy-all|chapter=Question 2|chapter-url=https://www.ipcc.ch/site/assets/uploads/2018/03/q1to9-1.pdf|access-date=2021-08-12|archive-date=2021-07-28|archive-url=https://web.archive.org/web/20210728102912/https://www.ipcc.ch/site/assets/uploads/2018/03/q1to9-1.pdf|url-status=live}}, in IPCC TAR SYR 2001 Q2 p 44</ref> These are "[[Bayesian probability|Bayesian]]" probabilities, which are based on an expert assessment of all the available evidence.<ref>{{citation|author=Ahmad, Q.K.|title=Sec. 2.6.2. "Objective" and "Subjective" Probabilities are not Always Explicitly Distinguished|df=dmy-all|chapter=Ch 2: Methods and Tools|chapter-url=https://www.ipcc.ch/site/assets/uploads/2018/03/wg2TARchap2.pdf|display-authors=etal|access-date=2021-08-12|archive-date=2021-08-08|archive-url=https://web.archive.org/web/20210808000331/https://www.ipcc.ch/site/assets/uploads/2018/03/wg2TARchap2.pdf|url-status=live}}, in IPCC TAR WG2 2001 Ch 2 p 129</ref><ref>
{{citation|author=Granger Morgan, M.|title=Synthesis and Assessment Product 5.2: Best practice approaches for characterizing, communicating, and incorporating scientific uncertainty in decisionmaking. A Report by the U.S. Climate Change Science Program (CCSP) and the Subcommittee on Global Change Research|url=http://www.climatescience.gov/Library/sap/sap5-2/final-report/sap5-2-final-report-all.pdf|df=dmy-all|year=2009|archive-url=https://web.archive.org/web/20130616035151/http://www.climatescience.gov/Library/sap/sap5-2/final-report/sap5-2-final-report-all.pdf|location=Washington D.C.|publisher=National Oceanic and Atmospheric Administration|display-authors=etal|archive-date=16 June 2013|url-status=dead}}, pp. 19–20, 27–28. [http://www.climatescience.gov/Library/sap/sap5-2/final-report/default.htm Report website.]  {{webarchive|url=https://web.archive.org/web/20091211193257/http://www.climatescience.gov/Library/sap/sap5-2/final-report/default.htm|date=11 December 2009}}
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<noinclude>"Robust findings" of the Synthesis Report include:
* "Observations show Earth's surface is warming. Globally, 1990s very likely warmest decade in [[instrumental temperature record|instrumental record]]".<ref name="TAR SPM robust findings">{{cite book |title=Synthesis Report of the IPCC Third Assessment Report: Summary for Policymakers |date=2001 |publisher=Cambridge University Press |isbn=0-521-80770-0 |url=https://www.ipcc.ch/report/ar3/syr/ |access-date=2021-08-12 |archive-date=2021-08-14 |archive-url=https://web.archive.org/web/20210814135724/https://www.ipcc.ch/report/ar3/syr/ |url-status=live }}</ref> Atmospheric concentrations of anthropogenic (i.e., human-emitted) [[greenhouse gas]]es have increased substantially.<ref name="TAR SPM robust findings" />
* Since the mid-20th century, most of the observed warming is "likely" (greater than 66% probability, based on expert judgement)<ref name="tar uncertainties" /> due to human activities.<ref name="TAR SPM robust findings" />
* Projections based on the ''[[Special Report on Emissions Scenarios]]'' suggest warming over the 21st century at a more rapid rate than that experienced for at least the last 10,000 years.<ref name="TAR SPM robust findings" />
* "Projected climate change will have beneficial and adverse effects on both environmental and socioeconomic systems, but the larger the changes and the rate of change in climate, the more the adverse effects predominate."<ref name="TAR SPM robust findings" />
* "[[Ecosystem]]s and [[species]] are [[Climate change vulnerability|vulnerable to climate change]] and other stresses (as illustrated by observed impacts of recent regional temperature changes) and some will be irreversibly damaged or lost."<ref name="TAR SPM robust findings" />
* "Greenhouse gas emission reduction ([[climate change mitigation|mitigation]]) actions would lessen the pressures on natural and human systems from climate change."<ref name="TAR SPM robust findings" />
* "[[climate change adaptation|Adaptation]] [to the effects of climate change] has the potential to reduce adverse [[effects of global warming|effects of climate change]] and can often produce immediate ancillary benefits, but will not prevent all damages."<ref name="TAR SPM robust findings" /> An example of adaptation to climate change is building [[levee]]s in response to [[current sea level rise|sea level rise]].<ref>{{citation|author=Nicholls, R.J.|title=Table 6.11|chapter=Ch 6: Coastal Systems and Low-Lying Areas|chapter-url=https://www.ipcc.ch/site/assets/uploads/2018/02/ar4-wg2-chapter6-1.pdf|display-authors=etal|access-date=2021-08-12|archive-date=2021-08-08|archive-url=https://web.archive.org/web/20210808003305/https://www.ipcc.ch/site/assets/uploads/2018/02/ar4-wg2-chapter6-1.pdf|url-status=live}}<nowiki>, in IPCC AR4 WG2 2007 Ch 6-1 p 343}}</nowiki></ref></noinclude>