Acceleration of Daily Land Temperature Extremes and Link to Land Forcing

We analyse a large number of Earth System Models (ESMs) and find that there is some evidence that the temperatures of extreme events are rising faster than local background rises in mean summer temperatures. We find this to be true for almost all land regions when analysing the SSP585 scenario and for the decades from now until the end of the 21^st Century. We find strong correlations between the level of acceleration and upward trends in sensible heat fluxes. In the few tropical regions where there is less correlation, we instead find a link to background latent plus sensible heat, which acts as a proxy for overall available energy. We then study extreme acceleration in the contemporary period, in both ESMs and ERA5 data. We find in these circumstances particularly strong evidence of faster warming of extreme events, but only for selected regions. We suggest this is a consequence of highly regional effects such as aerosols. Our analysis hints that as atmospheric composition changes move towards alteration by greenhouse gases only, there will be a more general globally-applicable occurrence of high-temperature extremes, with their mean increase more than the more general background warming levels.