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Climate models are one of the primary means for scientists to understand how the climate has changed in the past and may change in the future. These models simulate the physics, chemistry and biology of the atmosphere, land and oceans in great detail, and require some of the largest supercomputers in the world to generate their climate projections.
Climate models are constantly being updated, as different modelling groups around the world incorporate higher spatial resolution, new physical processes and biogeochemical cycles. These modelling groups coordinate their updates around the schedule of the Intergovernmental Panel on Climate Change (IPCC) assessment reports, releasing a set of model results – known as “runs” – in the lead-up to each one.
These coordinated efforts are part of the Coupled Model Intercomparison Projects (CMIP). The 2013 IPCC fifth assessment report (AR5) featured climate models from CMIP5, while the upcoming 2021 IPCC sixth assessment report (AR6) will feature new state-of-the-art CMIP6 models.
CMIP6 will consist of the “runs” from around 100 distinct climate models being produced across 49 different modelling groups. The effort is already a year behind schedule, and it appears increasingly unlikely that all the CMIP6 models will be available in time for inclusion in the AR6.