Fig. 3: Changes in European summer heatwave (EuSHW) intensity due to forced changes in internal variability.

a Detrended observed, historical and projected EuSHW intensity expressed as cumulative heat in the left y-axis and scaled it to the observed historical mean (1970–2022) in the right y-axis. Solid lines indicate the ensemble mean, the shading indicates the 5th and 95th percentile, and the right vertical bars indicate the 5th and 95th percentile for the last 20 years of the historical simulation and each shared socioeconomic pathway (SSP) scenario for ACCESS-ESM-1.5; b the forced signal (i.e., ensemble mean) of detrended EuSHW cumulative heat scaled to global mean temperature anomalies (GMTA) relative to 1985–2014 for SSP2–4.5 and SSP5–8.5 scenarios (2014–2100) for ACCESS-ESM-1.5; c the range (i.e., ensemble spread computed as ensemble standard deviation) of detrended EuSHW cumulative heat due to internal variability scaled to GMTA relative to 1985–2014 for SSP2–4.5 and SSP5–8.5 scenarios (2014–2100) for ACCESS-ESM-1.5; d–f same as (a–c) but for CanESM5; g–i same as (a–c) but for EC-Earth3; j–l same as (a–c) but for MIROC6; m–o same as (a–c) but for MPI-GE CMIP6.