CMIP6 GCM Validation Based on ECS and TCR Ranking for 21st Century Temperature Projections and Risk Assessment

Global climate models (GCMs) from the sixth Coupled Model Intercomparison Project Phases (CMIP6) have been employed to simulate twenty-first-century temperatures for risk assessment of future change. However, their transient response (TCR) ranges 1.2 2.8 °C, whereas equilibrium sensitivity (ECS) 1.8 5.7 leading large variations in climatic impact an anthropogenic increase atmospheric CO2 levels. Moreover, there is growing evidence that many GCMs are running “too hot” and hence unreliable directing policies changes. Here, I rank 41 CMIP6 according how successfully they hindcast global surface warming between 1980 2021 using both published ECS TCR estimates. The sub-ensemble with best performance appears be composed ranging 3.0 °C (which confirms previous studies) °C. This GCM made up a total 17 models. Depending on emission scenarios, these predict 2045–2055 1.5–2.5 compared pre-industrial era (1850–1900). As result, aggregated estimates seem moderate, which implies any negative effects change may adequately addressed by adaptation programs. also doubts regarding actual magnitude warming, might exaggerated because urban heat contamination other local non-climatic biases. A final section dedicated highlighting divergences observed temperature records number alternative reconstructions lower troposphere satellite measurements, tree-ring-width chronologies, based rural stations alone. If reported overestimated, real significantly than what produced GCMs, as some independent studies already suggested, would invalidate all GCMs.