Global warming is expected to increase the amount of atmospheric moisture, resulting in heavier extreme precipitation. Various studies have used the historical relationship between extreme precipitation and temperature (“temperature scaling”) to provide guidance about precipitation extremes in a future warmer climate. Here we assess how much information is required to robustly identify temperature scaling relationships, and whether these relationships are equally effective at different times in the future in estimating precipitation extremes everywhere across North America. Using a large ensemble of 35 North American regional climate simulations of the period 1951-2100, we show that individual climate simulations of length comparable to that of typical instrumental records are unable to constrain temperature scaling relationships well enough to reliably estimate future extremes of local precipitation accumulation for hourly to daily durations in the model’s climate. Hence, temperature scaling relationships estimated from the limited historical observations are unlikely to be able to provide reliable guidance for future adaptation planning at local spatial scales. Well-constrained temperature scaling relations do provide a feasible basis for accurately projecting future precipitation extremes for hourly to daily durations over more than 90% of the North American land area. While simulations that are equivalent in length of many multiples of historical observational records are required to robustly identify those relationships, the cost of producing sufficient simulations to well constrain those relations is substantially lower than the cost of producing larger ensembles of simulations for the direct estimation of changes in extremes.

This is work with a research associate and some colleagues at Environment and Climate Change Canada. The paper that reports this work is currently under review for consideration by Earth’s Future, a journal of the American Geophysical Union.