4.1 What kind of models are used for climate projections in IPCC reports?

Climate projections (e. g. figure 14) presented in IPCC (Intergovernmental Panel on Climate Change) reports are based on simulations with different climate models. There are around 40 climate models around the world, including models in the United States, Japan, China, France, United Kingdom, Germany, Canada. They all perform the same simulations as part of the Coupled Model Intercomparison Project (CMIP). All results are freely accessible on the web. These results are used in IPCC reports. For example, the 5th IPCC report ([IPCC, 2013]) used results from CMIP5 ([Taylor et al., 2012]).

Figure 14: Temperature evolution from 1950 to 2100 simulated by models participating in CMIP5. Until the early 2000s, the simulations are forced by observed concentrations of greenhouse gases and aerosols. Beyond, simulations are forced according to two types of scenarios: optimistic (blue) or pessimistic (red). The colored envelopes represent all the models, while the solid lines represent the multi-model mean.