Advanced Testing of Low, Medium, and High ECS CMIP6 GCM Simulations Versus ERA5‐T2m

Abstract

Abstract The equilibrium climate sensitivity (ECS) of the CMIP6 global circulation models (GCMs) varies from 1.83°C to 5.67°C. Herein, 38 GCMs are grouped into three ECS classes (low, 1.80–3.00°C; medium, 3.01–4.50°C; high, 4.51–6.00°C) and compared against the ERA5‐T2m records from 1980–1990 to 2011–2021. We found that all models with ECS > 3.0°C overestimate the observed global surface warming and that spatial t‐statistics rejects the data‐model agreement over 60% (using low‐ECS GCMs) to 81% (using high‐ECS GCMs) of the Earth's surface. Thus, the high and medium‐ECS GCMs are unfit for prediction purposes. The low‐ECS GCMs are not fully satisfactory yet, but they are also found unalarming because by 2050 they predict a moderate warming (Δ T preindustrial →2050 ≲ 2°C).

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