The Role of the IPCC in Climate Science
Authors: Meehl Gerald A. 
Published: April 2023

The Intergovernmental Panel on Climate Change (IPCC) consists of about 190 governments that commission assessments performed by the international climate science community to determine the current state of human knowledge of climate and climate change. As such, the IPCC does not perform scientific research, but, rather, assesses research in the form of published papers addressing topics in climate science related to climate variability and change. However, as the IPCC assessments have evolved (from the first in 1990 to the sixth in 2021, so far), the IPCC has formed a symbiotic relationship with climate science. Even though the goal of the IPCC is to assess the scientific research that is taking place, its high profile, prestige, and interest from governments that fund climate science research has stimulated and arguably accelerated climate science research. This is particularly relevant for Earth system modeling (including the physical climate system plus the biogeochemical components) that will be addressed here to illustrate the influence of IPCC on climate science. One outcome is that enhanced observations of the Earth system from a number of field campaigns have been funded by countries to gather targeted observations to improve the understanding of crucial processes that need to be represented with fidelity in Earth system models. Governments that fund Earth system modeling research want to have results from their model appear prominently in the IPCC assessments to partially justify the funds being spent on developing, running, and analyzing these models. And just as important as getting a model into the IPCC assessment process are the analyses of the model outputs done by the scientists in the modeling groups and other scientists around the world. The products of this process are the papers describing cutting-edge results that use the models to advance knowledge of climate variability and change. Therefore, model developers are competing with other modeling groups around the world to have the best possible models producing climate simulations that are analyzed to produce papers of the highest quality that are assessed in the IPCC reports. An important part of this process is the international scientific coordination provided by the World Climate Research Programme’s Coupled Model Intercomparison Project (CMIP). CMIP involves climate scientists from around the world who volunteer their time to organize CMIP while also developing climate models in their respective countries. CMIP started in the mid-1990s for modeling groups to run exactly the same experiments so the response across the models could be directly compared to quantify uncertainty in their simulations of historical and future climate. Because these climate experiments are, by construction, the current state-of-the-art in climate modeling with the best representation of human understanding of the workings of the climate system, the papers that are written based on those model integrations are of primary interest for the IPCC assessments. CMIP has since evolved to include numerous climate science communities that interface with the modeling groups to perform model intercomparison projects to address various compelling climate science problems. Thus, there is a symbiosis between climate science/modeling, the scientific framework provided by CMIP for coordinated climate change experiments, and the IPCC process that assesses papers that emerge from the scientific research done by scientists who desire their work to be featured in those prestigious IPCC assessments.