When will we detect changes in short-duration precipitation extremes?

The question of when we may be able to detect the influence of climate change on UK rainfall extremes is important from a planning perspective, providing a timescale for necessary climate change adaptation measures. Short-duration intense rainfall is responsible for flash flooding, and several studies have suggested an amplified response to warming for rainfall extremes on hourly and sub-hourly timescales. However, there are very few studies examining the detection of changes in sub-daily rainfall. This is due to the high cost of very high-resolution (kilometre-scale) climate models needed to capture hourly rainfall extremes, and to a lack of sufficiently long high-quality sub-daily observational records. Results here using output from a 1.5km climate model over the southern UK indicate that changes in 10-minute and hourly precipitation emerge before changes in daily precipitation. In particular, model results suggest detection times for short-duration rainfall intensity in the 2040s in winter and 2080s in summer, which are respectively 5-10 years and decades earlier than for daily extremes. Results from a new quality-controlled observational dataset of hourly rainfall over the UK do not show a similar difference between daily and hourly trends. Natural variability appears to dominate current observed trends (including an increase in the intensity of heavy summer rainfall over the last 30 years), with some suggestion of larger daily than hourly trends for recent decades. The expectation of the reverse, namely larger trends for short-duration rainfall, as the signature of underlying climate change has potentially important implications for detection and attribution studies