Extended Data Fig. 6: Comparison between simulated changes in MHW characteristics exceeding the 99th percentile from a natural-forcing simulation and from a preindustrial control simulation using GFDL ESM2M forced with the RCP 8.5 scenario over the 21st century.

a–d, The probability ratio (a), annual mean duration (b), maximum annual intensity (c) and annual cumulative mean intensity (d) of MHWs. The red line shows the simulated changes exceeding the 99th percentile from a natural-forcing simulation of GFDL ESM2M forced with observed solar and volcanic boundary conditions, but with greenhouse gases and aerosol concentrations set to preindustrial. The black line shows the simulated changes exceeding the preindustrial 99th percentile. The time series are smoothed with a 20-year running mean.