Editing General circulation model (section)

===Model accuracy===
{{Update section|date=August 2015}}
[[Image:Hadcm3-era-sst-annual.png|thumb|SST errors in HadCM3]]
[[File:Climate model NA annual precipitation 2002.jpg|thumb|North American precipitation from various models]] [[File:Global Warming Predictions.png|thumb|Temperature predictions from some climate models assuming the SRES A2 emissions scenario]]

AOGCMs internalise as many processes as are sufficiently understood. However, they are still under development and significant uncertainties remain. They may be coupled to models of other processes in [[Earth system model]]s, such as the [[carbon cycle]], so as to better model feedback. Most recent simulations show "plausible" agreement with the measured temperature anomalies over the past 150 years, when driven by observed changes in greenhouse gases and aerosols. Agreement improves by including both natural and anthropogenic forcings.<ref name="f4">IPCC, [http://www.grida.no/climate/ipcc_tar/wg1/005.htm Summary for Policy Makers] {{webarchive|url=https://web.archive.org/web/20160307220102/http://www.grida.no/climate/ipcc_tar/wg1/005.htm |date=7 March 2016 }}, [http://www.grida.no/publications/other/ipcc%5Ftar/?src=/climate/ipcc_tar/wg1/figspm-4.htm Figure 4] {{webarchive|url=https://web.archive.org/web/20161021094407/http://www.grida.no/publications/other/ipcc_tar/?src=%2Fclimate%2Fipcc_tar%2Fwg1%2Ffigspm-4.htm |date=21 October 2016 }}, in {{citation 
 |year=2001 
 |author=IPCC TAR WG1 
 |author-link=IPCC 
 |title=Climate Change 2001: The Scientific Basis 
 |series=Contribution of Working Group I to the [[IPCC Third Assessment Report|Third Assessment Report]] of the Intergovernmental Panel on Climate Change 
 |editor=Houghton, J. T. 
 |editor2=Ding, Y. 
 |editor3=Griggs, D. J. 
 |editor4=Noguer, M. 
 |editor5=van der Linden, P. J. 
 |editor6=Dai, X. 
 |editor7=Maskell, K. 
 |editor8=Johnson, C. A. 
 |publisher=Cambridge University Press 
 |url=https://archive.org/details/climatechange2000000unse 
 |isbn=978-0-521-80767-8 
 |url-status=dead 
 |url-access=registration|archive-url=https://web.archive.org/web/20191215120519/https://archive.org/details/climatechange2000000unse 
 |archive-date=15 December 2019 
 }} (pb: {{ISBNT|0-521-01495-6}}).</ref><ref>{{cite web|title=Simulated global warming 1860–2000 |url=http://www.hadleycentre.gov.uk/research/hadleycentre/pubs/talks/sld017.html |url-status=dead |archive-url=https://web.archive.org/web/20060527001324/http://www.hadleycentre.gov.uk/research/hadleycentre/pubs/talks/sld017.html |archive-date=27 May 2006 }}</ref><ref>{{cite web|title = Decadal Forecast 2013|url = https://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/long-range/decadal-fc/2013 |website = Met Office|date = January 2014}}</ref>

Imperfect models may nevertheless produce useful results. GCMs are capable of reproducing the general features of the observed global temperature over the past century.<ref name="f4" />

A debate over how to reconcile climate model predictions that upper air (tropospheric) warming should be greater than observed surface warming, some of which appeared to show otherwise,<ref>The National Academies Press website press release, 12 Jan. 2000: 
 [https://web.archive.org/web/20060420125451/http://www4.nationalacademies.org/news.nsf/isbn/0309068916?OpenDocument Reconciling Observations of Global Temperature Change].</ref> was resolved in favour of the models, following data revisions.

[[clouds|Cloud]] effects are a significant area of uncertainty in climate models. Clouds have competing effects on climate. They cool the surface by reflecting sunlight into space; they warm it by increasing the amount of infrared radiation transmitted from the atmosphere to the surface.<ref>[https://web.archive.org/web/20000901022925/http://liftoff.msfc.nasa.gov/academy/space/greenhouse.html Nasa Liftoff to Space Exploration Website: Greenhouse Effect]. Archive.com. Recovered 1 October 2012.</ref> In the 2001 IPCC report possible changes in cloud cover were highlighted as a major uncertainty in predicting climate.<ref>{{cite web|url =http://webpages.icav.up.pt/PTDC/CVT/098487/2008/IPPC,%202001.pdf |title = Climate Change 2001: The Scientific Basis|publisher = IPCC|page = 90}}</ref><ref>{{cite journal |last1=Soden |first1= Brian J.|first2=Isaac M. |last2=Held |year=2006 |title=An Assessment of Climate Feedbacks in Coupled Ocean–Atmosphere Models |journal=J. Climate |volume = 19|issue= 14 |pages= 3354–3360 |doi= 10.1175/JCLI3799.1 |bibcode = 2006JCli...19.3354S |doi-access=free }}</ref>

Climate researchers around the world use climate models to understand the climate system. Thousands of papers have been published about model-based studies. Part of this research is to improve the models.

In 2000, a comparison between measurements and dozens of GCM simulations of [[ENSO]]-driven tropical precipitation, water vapor, temperature, and outgoing longwave radiation found similarity between measurements and simulation of most factors. However, the simulated change in precipitation was about one-fourth less than what was observed. Errors in simulated precipitation imply errors in other processes, such as errors in the evaporation rate that provides moisture to create precipitation. The other possibility is that the satellite-based measurements are in error. Either indicates progress is required in order to monitor and predict such changes.<ref>{{cite journal|title = The Sensitivity of the Tropical Hydrological Cycle to ENSO |first = Brian J.|last = Soden|date = February 2000|journal = Journal of Climate|volume = 13|issue = 3 |pages =  538–549|doi = 10.1175/1520-0442(2000)013<0538:TSOTTH>2.0.CO;2 |bibcode = 2000JCli...13..538S| s2cid=14615540 |doi-access = free}}</ref>

The precise magnitude of future changes in climate is still uncertain;<ref>Cubasch ''et al.'', [http://www.grida.no/climate/ipcc_tar/wg1/338.htm Chapter 9: Projections of Future Climate Change] {{webarchive|url=https://web.archive.org/web/20160416080318/http://www.grida.no/climate/ipcc_tar/wg1/338.htm |date=16 April 2016 }}, [http://www.grida.no/climate/ipcc_tar/wg1/339 Executive Summary] {{dead link|date=February 2018|bot=medic}}{{cbignore|bot=medic}}, in {{Citation 
 |year=2001 
 |author=IPCC TAR WG1 
 |author-link=IPCC 
 |title=Climate Change 2001: The Scientific Basis 
 |series=Contribution of Working Group I to the [[IPCC Third Assessment Report|Third Assessment Report]] of the Intergovernmental Panel on Climate Change 
 |editor=Houghton, J. T. 
 |editor2=Ding, Y. 
 |editor3=Griggs, D. J. 
 |editor4=Noguer, M. 
 |editor5=van der Linden, P. J. 
 |editor6=Dai, X. 
 |editor7=Maskell, K. 
 |editor8=Johnson, C. A. 
 |publisher=Cambridge University Press 
 |url=https://archive.org/details/climatechange2000000unse 
 |isbn=978-0-521-80767-8 
 |url-status=dead 
 |url-access=registration
 |archive-url=https://web.archive.org/web/20191215120519/https://archive.org/details/climatechange2000000unse 
 |archive-date=15 December 2019 
 }} (pb: {{ISBNT|0-521-01495-6}}).</ref> for the end of the 21st century (2071 to 2100), for SRES scenario A2, the change of global average SAT change from AOGCMs compared with 1961 to 1990 is +3.0&nbsp;°C (5.4&nbsp;°F) and the range is +1.3 to +4.5&nbsp;°C (+2.3 to 8.1&nbsp;°F).

The IPCC's [[IPCC AR5|Fifth Assessment Report]] asserted "very high confidence that models reproduce the general features of the global-scale annual mean surface temperature increase over the historical period". However, the report also observed that the rate of warming over the period 1998–2012 was lower than that predicted by 111 out of 114 [[Coupled Model Intercomparison Project]] climate models.<ref>{{cite web | url=http://www.climatechange2013.org/images/report/WG1AR5_Chapter09_FINAL.pdf | title=Evaluation of Climate Models | publisher=[[IPCC]] | date=2013| author=Flato, Gregory | pages=768–769}}</ref>