Changes in the Frequency of Observed Temperature Extremes Largely Driven by a Distribution Shift

Abstract Extreme heat poses significant threats to human life and ecosystems. Quantifying the effects of anthropogenic climate change on extreme heat has remained challenging, in part due to the short observational record. Here, we isolate the most slowly varying component of the frequency at which the historical 90th and 99th percentiles were exceeded in observational records from 1955 to 2021 by using a statistical method called low‐frequency component analysis. The emerging spatiotemporal signal in the changing frequency of temperature extremes can be attributed to a shift of the temperature distribution by local warming of the annual‐mean daily maximum temperature. The shift explains over 80% of the interannual variability in the frequency at which the historical 90th percentile is exceeded in the tropics and up to 50% in higher latitudes. This work connects variability in the frequency of extreme surface temperatures to variability in mean local warming.