Extreme daily precipitation is thought to increase with warming at a rate of 6.5% per K. High-resolution simulations for the southern UK show this scaling for present conditions, but above 22 °C this scaling fails owing to changes in dynamics. Extreme daily precipitation is thought to increase with temperature at a rate of 6.5% per K according to the Clausius–Clapeyron relationship between temperature and saturation vapour pressure1. A wide range of scaling relationships has been observed globally for extreme daily and hourly precipitation, with evidence of scaling above 6.5% per K for sub-daily extreme precipitation in some regions2,3,4. Only high-resolution climate models can simulate this scaling relationship5. Here we examine the scaling of hourly extreme precipitation intensities in a future climate using experiments with a model for the southern UK with kilometre-scale resolution6. Our model simulates the present-day scaling relationship at 6.5% per K, in agreement with observations. The simulated overall future increase in extreme precipitation follows the same relationship. However, UK extreme precipitation intensities decline at temperatures above about 22 °C—a temperature range that is not well sampled in the present-day integration—as a result of a more frequent occurrence of anticyclonic weather systems. Anticyclones produce more days with strong daytime heating, but are not favourable to the development of deep intense convective storms. We conclude that future extreme hourly precipitation intensities cannot simply be extrapolated from present-day temperature scaling, and demonstrate the pitfalls of using regional surface temperature as a scaling variable.
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