Abstract/Summary

Warming of climate is intensifying the global water cycle, including the rate of fresh water flux between the atmosphere and surface, determined by precipitation minus evaporation (P−E). Surplus or deficit in fresh water impacts societies and ecosystems so it is important to monitor and understand how and why P−E patterns and their seasonal range are changing across the globe. Here, annual maximum and minimum P−E and their changes are diagnosed globally over land and ocean in observations-based datasets and CMIP6 climate model experiments from 1950-2100. Seasonal minimum P−E is negative across much of the globe apart from the Arctic, mid-latitude oceans and the tropical warm pool. In the global mean, P−E maximum increases and P−E minimum decreases by around 3-4% per oC of global warming from 1995-2014 to 2080-2100 in the ensemble mean of an intermediate greenhouse gas emissions scenario. Over land, there is less coherence across datasets 1960-2020 but an increase in the seasonal range in P−E also emerges in future projections. Patterns of future changes in annual maximum and minimum P−E are qualitatively similar to present day trends with increases in maximum P−E in the equatorial belt and high latitude regions and decreases in the subtropical subsidence zones. This adds confidence to future projections of a more variable and extreme water cycle but also highlights uncertainties in this response over land.