Observed Increases in Probable Maximum Precipitation Over Global Land Areas

One of the more robust signals of climate change is an increase in heavy precipitation events, both in the observed record and in climate model simulations of the future. Observed increases have been documented in many regions of the globe (IPCC 2012) and it is expected, based on climate model simulations that most of these same regions will continue to see increases in heavy precipitation events. One result from these changes is a demand from decision makers, particularly those charged with overseeing the construction of long-lived hydrological infrastructure, is how applied climatology products used in design of these structures might change in the future. One such product is Probable Maximum Precipitation, which is an estimate of the largest amount of rainfall that could theoretically occur for a specified period (e.g. 24h). Here we examine observed changes in PMP looking at the difference between PMP estimates for the 1951-1980 period and PMP estimates for the 1981-2010 period. Increases are found over most global land areas, with changes as large as +20% or more.