View source for Coupled Model Intercomparison Project

{{Short description|Collaboration for climate change study}}
{{Technical|date=November 2021}}

In [[climatology]], the '''Coupled Model Intercomparison Project''' (CMIP) is a collaborative framework designed to improve knowledge of [[climate change]]. It was organized in 1995 by the Working Group on Coupled Modelling (WGCM) of the [[World Climate Research Programme]] (WCRP). It is developed in phases to foster the climate model improvements but also to support national and international assessments of climate change. A related project is the [[Atmospheric Model Intercomparison Project]] (AMIP) for global coupled ocean-atmosphere [[general circulation model]]s (GCMs).

Coupled models are computer-based models of the Earth's climate, in which different parts (such as atmosphere, oceans, land, ice) are "coupled" together, and interact in simulations.<ref name="Meehl1997" /> 

== CMIP phases ==

The [[Program for Climate Model Diagnosis and Intercomparison]] (PCMDI) at [[Lawrence Livermore National Laboratory]] has been supporting the several CMIP phases by helping WGCM to determine the scope of the project, by maintaining the project's data base and by participating in data analysis. CMIP has received model output from the pre-industrial climate simulations ("control runs") and 1% per year increasing-CO<sub>2</sub> simulations of about 30 coupled GCMs. More recent phases of the project,{{update|date=April 2023|reason=20C3M is from 2002/2003 and is not recent}} including 20th Century Climate in Coupled Models (20C3M), include more realistic scenarios of climate forcing for both historical, paleoclimate and future scenarios.

=== CMIP Phases 1 and 2 ===
The response to the CMIP1 announcement was very successful and up to 18 global coupled models participated in the data collection representing most of the international groups with global coupled GCMs.<ref name="Meehl1997">[https://doi.org/10.1029/97EO00276 Intercomparison makes for a better climate model], Gerald A. Meehl, George J. Boer, Curt Covey, Mojib Latif, Ronald J. Stouffer, [[Eos (magazine)|Eos]], Vol. 78, No. 41, October 14, 1997</ref> In consequence, at the September 1996 meeting of the [[CLIVAR]] NEG2 numerical experimentation group in [[Victoria, Canada]], it was decided that CMIP2 will be an inter-comparison of 1% per year compound {{CO2|link=yes}} increase integrations (80 years in length) where {{CO2}} doubles at around year 70.

=== CMIP Phase 3 ===
During 2005 and 2006, a collection of climate model outputs was coordinated and stored by PCMDI.<ref>{{Cite web|url=https://pcmdi.llnl.gov/mips/cmip3/ |title=CMIP3-Info |website=pcmdi.llnl.gov|language=en|access-date=2018-05-20}}</ref> The climate model outputs included simulations of past, present and future climate scenarios. This activity enabled those climate models, outside the major modeling centers to perform research of relevance to climate scientists preparing the [[IPCC Fourth Assessment Report]] (IPCC-AR4). For the CMIP3 a list of 20 different experiments were proposed,<ref>{{Cite web|url=https://pcmdi.llnl.gov/ipcc/standard_output.html#Experiments|title=CMIP3-Experiments |website=pcmdi.llnl.gov|language=en|access-date=2018-05-20 }}</ref> and the PCMDI kept the  documentation of all the global climate model involved.<ref>{{Cite web|url=https://pcmdi.llnl.gov/ipcc/model_documentation/ipcc_model_documentation.html  |title=CMIP3-Models |website=pcmdi.llnl.gov|language=en|access-date=2018-05-20}}</ref> Additional information and data-sets are in.<ref>{{Cite web|url=https://cmip.llnl.gov/cmip3_overview.html|title=CMIP3-Overview|website=cmip.llnl.gov|language=en|access-date=2018-05-20|archive-url=https://web.archive.org/web/20180523011722/https://cmip.llnl.gov/cmip3_overview.html|archive-date=2018-05-23|url-status=dead}}</ref>

=== CMIP Phase 5 ===
The next phase of the project (2010–2014) was CMIP5.<ref>{{Cite web|url=https://esgf-node.llnl.gov/projects/esgf-llnl/|title=ESGF-LLNL - Home {{!}} ESGF-CoG|website=esgf-node.llnl.gov|language=en|access-date=2017-10-09}}</ref><ref>{{Cite news|url=https://www.economist.com/news/science-and-technology/21729423-new-estimates-permissible-carbon-dioxide-emissions-notwithstanding-there|title=There is still no room for complacency in matters climatic|newspaper=The Economist|access-date=2017-10-09|language=en}}</ref> CMIP5 included more [[metadata]] describing model simulations than previous phases. The [[METAFOR]] project created an exhaustive [[Conceptual model|schema]] describing the scientific, technical, and numerical aspects of CMIP runs which was archived along with the output data.

A main objective of the CMIP5 experiments was to address outstanding scientific questions that arose as part of the IPCC AR4 process, improve understanding of climate, and to provide estimates of future climate change that will be useful to those considering its possible consequences. The [[IPCC Fifth Assessment Report]] summarizes information of CMIP5 experiments, while the CMIP5 experimental protocol was endorsed by the 12th Session of the WCRP Working on  this Group on Coupled Modelling (WGCM).<ref name="CMIP5Design">{{
cite journal
| last1=Taylor
| first1=K. E.
| last2=Stouffer
| first2=R. J.
| last3=Meehl
| first3=G. A. 
| date=2012-03-01
| title=An Overview of CMIP5 and the Experiment Design
| journal= Bulletin of the American Meteorological Society
| volume=93
| issue=4
| pages=485–498
| doi=10.1175/BAMS-D-11-00094.1
| bibcode=2012BAMS...93..485T
| doi-access=free
}}</ref> Additional information and data-sets are in.<ref>{{Cite web|url=https://cmip.llnl.gov/cmip5/index.html|title=CMIP5-Overview|website=cmip.llnl.gov|language=en|access-date=2018-05-20|archive-url=https://web.archive.org/web/20170124025620/http://cmip.llnl.gov/cmip5/index.html|archive-date=2017-01-24|url-status=dead}}</ref>

=== CMIP Phase 6 ===
[[File:SSPs-CMIP6.svg|thumb|SSP-RF scenario matrix, utilizing CMIP6]]
Planning meetings for Phase 6 began in 2013, and an overview of the design and organization was published in 2016. By 2018 CMIP6 had endorsed 23 Model Intercomparison Projects (MIPs) involving 33 modeling groups in 16 countries. A small number of common experiments were also planned. The deadline for submission of papers to contribute to the IPCC [[6th Assessment Report]] Working Group I is early 2020.<ref>{{cite web |last1=Eyring |first1=Veronika |display-authors=et al |title=Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) Experimental Design and Organization |url=https://www.wcrp-climate.org/images/modelling/WGCM/CMIP/CMIP6FinalDesign_GMD_180329.pdf |accessdate=6 July 2018}}</ref>

The '''structure of the CMIP6''' has been extended with respect to CMIP5 by providing an equivalent framework named CMIP Diagnostic, Evaluation and Characterization of Klima (DECK) (klima is Greek for "climate"), together with a set of Endorsed MIPs   to improve the description of aspects of climate models beyond the core set of common experiments included in DECK. However, CMIP-Endorsed Model Intercomparison Projects (MIPs) are still built on the DECK and CMIP historical simulations, therefore their main goal is just to address a wider range of specific questions.<ref>{{Cite web|url=https://www.wcrp-climate.org/modelling-wgcm-mip-catalogue/modelling-wgcm-cmip6-endorsed-mips|title = CMIP6-Endorsed MIPs| date=30 May 2023 }}</ref> This structure will be kept in future CMIP experiments.

CMIP6 also aims to be consistent regarding common standards and documentation. To achieve that it includes methods to facilitate a wider distribution and characterization of model outputs, and common standard tools for their analyses. A number of guides has been created<ref>{{Cite web|url=https://www.wcrp-climate.org/wgcm-cmip/wgcm-cmip6|title=CMIP6|date=2 December 2022 }}</ref> for data managers, modelers and users.

A set of official/common forcings datasets are available for the studies under DECK, as well as several MIPS.<ref>{{Cite news|url=https://docs.google.com/document/d/1pU9IiJvPJwRvIgVaSDdJ4O0Jeorv_2ekEtted34K9cA/edit#heading=h.jdoykiw7tpen|title=CMIP6_Forcing_Datasets_Summary|work=Google Docs|access-date=2018-07-18|language=en}}</ref> That allows for more sensible comparisons on the model ensemble created under the CMIP6 umbrella.

These '''common dataset forcings'''<ref>{{Cite web|url=https://www.wcrp-climate.org/wgcm-cmip/wgcm-cmip6?view=article&id=1321:modelling-wgcm-cmip6-historycmip6forcings&catid=55|title=History of CMIP6 Forcings|date=2 December 2022 }}</ref> are stored and coordinated by input4MIPS (input datasets for Model Intercomparison Projects).<ref>{{Cite web|url=https://esgf-node.llnl.gov/projects/input4mips/|title=input4MIPs - Home &#124; ESGF-CoG|website=esgf-node.llnl.gov}}</ref>
* Historical Short-Lived Climate Forcers (SLCF) and greenhouse gas ({{CO2}} and CH<sub>4</sub>) Emissions
* Biomass Burning Emissions
* Global Gridded Land-use Forcing Datasets<ref>{{Cite web|url=http://luh.umd.edu/|title=Land Use Harmonization|website=luh.umd.edu}}</ref>
* Historical [[greenhouse gas]]es concentrations: a full description is published <ref>{{Cite journal|last1=Meinshausen|first1=M.|last2=Vogel|first2=E.|last3=Nauels|first3=A.|last4=Lorbacher|first4=K.|last5=Meinshausen|first5=N.|last6=Etheridge|first6=D. M.|last7=Fraser|first7=P. J.|last8=Montzka|first8=S. A.|last9=Rayner|first9=P. J.|date=2017-05-31|title=Historical greenhouse gas concentrations for climate modelling (CMIP6)|journal=Geosci. Model Dev.|volume=10|issue=5|pages=2057–2116|doi=10.5194/gmd-10-2057-2017|issn=1991-9603|url=https://www.research-collection.ethz.ch/bitstream/20.500.11850/205639/1/gmd-10-2057-2017.pdf|bibcode=2017GMD....10.2057M|doi-access=free}}</ref> via the CMIP6 Special Issue publication<ref>{{Cite journal|url=https://www.geosci-model-dev.net/special_issue590.html|title=GMD – Special issue – Coupled Model Intercomparison Project Phase 6 (CMIP6) Experimental Design and Organization}}</ref>
* [[Ozone depletion and climate change|Ozone]] Concentrations and Nitrogen (N)-Deposition;<ref>{{Cite web|url=https://blogs.reading.ac.uk/ccmi/forcing-databases-in-support-of-cmip6/|title=Forcing Databases in Support of CMIP6 – Chemistry-Climate Model Initiative|website=blogs.reading.ac.uk}}</ref> description of ozone radiative forcing based on this dataset is published.<ref>{{Cite journal|last1=Checa-Garcia|first1=Ramiro|last2=Hegglin|first2=Michaela I.|last3=Kinnison|first3=Douglas|last4=Plummer|first4=David A.|last5=Shine|first5=Keith P.|date=2018-04-06|title=Historical Tropospheric and Stratospheric Ozone Radiative Forcing Using the CMIP6 Database|journal=Geophysical Research Letters|language=en|volume=45|issue=7|pages=3264–3273|doi=10.1002/2017gl076770|issn=0094-8276|bibcode=2018GeoRL..45.3264C|url=http://centaur.reading.ac.uk/75867/8/Checa-Garcia_et_al-2018-Geophysical_Research_Letters.pdf|doi-access=free}}</ref>
* [[Aerosol Optical Depth|Aerosol Optical Properties]] and Relative Change in Cloud Droplet Number Concentration<ref>[https://www.geosci-model-dev.net/10/433/2017/gmd-10-433-2017.pdf available as supplement to Stevens et al. (2016) here]</ref><ref>{{Cite journal|last1=Stevens|first1=B.|last2=Fiedler|first2=S.|last3=Kinne|first3=S.|last4=Peters|first4=K.|last5=Rast|first5=S.|last6=Müsse|first6=J.|last7=Smith|first7=S. J.|last8=Mauritsen|first8=T.|date=2017-02-01|title=MACv2-SP: a parameterization of anthropogenic aerosol optical properties and an associated Twomey effect for use in CMIP6|journal=Geosci. Model Dev.|volume=10|issue=1|pages=433–452|doi=10.5194/gmd-10-433-2017|issn=1991-9603|bibcode=2017GMD....10..433S|doi-access=free|hdl=11858/00-001M-0000-002B-077D-D|hdl-access=free}}</ref>
* [[Solar forcing|Solar Forcing]]:<ref>{{Cite web|url=http://solarisheppa.geomar.de/cmip6|title=CMIP6 recommendations &#124; SOLARIS HEPPA|website=solarisheppa.geomar.de}}</ref><ref>{{Cite journal|last1=Matthes|first1=K.|last2=Funke|first2=B.|last3=Andersson|first3=M. E.|last4=Barnard|first4=L.|last5=Beer|first5=J.|last6=Charbonneau|first6=P.|last7=Clilverd|first7=M. A.|last8=Dudok de Wit|first8=T.|last9=Haberreiter|first9=M.|date=2017-06-22|title=Solar forcing for CMIP6 (v3.2)|journal=Geosci. Model Dev.|volume=10|issue=6|pages=2247–2302|doi=10.5194/gmd-10-2247-2017|issn=1991-9603|bibcode=2017GMD....10.2247M|doi-access=free|hdl=10261/164552|hdl-access=free}}</ref>
* [[Stratospheric aerosol layer|Stratospheric Aerosol]] Data Set<ref>[ftp://iacftp.ethz.ch/pub_read/luo/CMIP6 data are available here]</ref>
* AMIP [[Sea surface temperature|Sea Surface Temperature]] and Sea Ice Datasets

Beyond these historical forcings, CMIP6 also has a common set of future scenarios comprising land use and emissions as required for the future [[Shared Socioeconomic Pathways]] (SSPs) which have replaced the  [[Representative Concentration Pathways]] (RCPs) from prior models.<ref>{{Cite journal|last1=O'Neill|first1=B. C.|last2=Tebaldi|first2=C.|last3=van Vuuren|first3=D. P.|last4=Eyring|first4=V.|last5=Friedlingstein|first5=P.|last6=Hurtt|first6=G.|last7=Knutti|first7=R.|last8=Kriegler|first8=E.|last9=Lamarque|first9=J.-F.|date=2016-09-28|title=The Scenario Model Intercomparison Project (ScenarioMIP) for CMIP6|journal=Geosci. Model Dev.|volume=9|issue=9|pages=3461–3482|doi=10.5194/gmd-9-3461-2016|issn=1991-9603|bibcode=2016GMD.....9.3461O|doi-access=free|hdl=20.500.11850/121420|hdl-access=free}}</ref>

=== CMIP Phase 7 ===
First data is expected end-2025.<ref>{{Cite news |title=Supercomputers and AI are helping build better climate models |url=https://www.economist.com/the-world-ahead/2024/11/20/supercomputers-and-ai-are-helping-build-better-climate-models |access-date=2025-01-23 |work=The Economist |issn=0013-0613}}</ref> For CMIP7 a more continuous release approach than in previous phases was announced: In addition to DECK releases and a growing number of community MIPS, so-called fast track experiments supporting specific requirements will be released.<ref>{{Cite web |date=2023-03-17 |title=CMIP Phase 7 (CMIP7) - Coupled Model Intercomparison Project |url=https://wcrp-cmip.org/cmip-phases/cmip7/# |access-date=2025-05-22 |language=en-GB}}</ref>

== See also ==
* [[Climate model]]
* [[Intergovernmental Panel on Climate Change]]
* [[Representative Concentration Pathway]]
* [[Shared Socioeconomic Pathways]]

== References ==
{{Reflist|30em}}

== External links ==
* [https://wcrp-cmip.org/ Coupled Model Intercomparison Project (CMIP)]
* [https://web.archive.org/web/20170522131654/http://www-pcmdi.llnl.gov/projects/cmip/overview_ms/ms_text.php  An Overview of Results from the Coupled Model Intercomparison Project (CMIP)]
* [https://wcrp-cmip.org/model-intercomparison-projects-mips/ MIPS Overview, included CMIP1 to CMIP5 phases]
* [https://wcrp-cmip.org/cmip-phase-5-cmip5/ CMIP5 Summary]
* [https://pcmdi.llnl.gov/mips/cmip5/experiment_design.html CMIP5 Design Documents]
* [https://wcrp-cmip.org/cmip-phase-6-cmip6/ CMIP6 homepage (WCRP)]
* [https://cmip-publications.llnl.gov/ CMIP Related Publications]

{{Atmospheric, Oceanographic and Climate Models}}{{Climate change}}
[[Category:Numerical climate and weather models]]