Climate change will affect global water availability through compounding changes in seasonal precipitation and evaporation

TLDR

Seasonal and annual precipitation and evaporation shape water availability, yet most climate studies ignore these patterns from a non‑parametric statistical perspective. The study aims to classify global land regions into nine seasonal hydroclimatic regimes using a non‑parametric framework based on late‑20th‑century precipitation means and seasonality. The regimes are then applied to CMIP5 future climate projections to evaluate how concurrent changes in mean and seasonal precipitation and evaporation affect water availability. Four of the nine regimes exhibit increased precipitation variability, while five show reduced evaporation variability alongside rising mean precipitation and evaporation; highly variable regimes become even more variable, whereas low‑seasonality regimes receive more wet‑season precipitation.

Abstract

Both seasonal and annual mean precipitation and evaporation influence patterns of water availability impacting society and ecosystems. Existing global climate studies rarely consider such patterns from non-parametric statistical standpoint. Here, we employ a non-parametric analysis framework to analyze seasonal hydroclimatic regimes by classifying global land regions into nine regimes using late 20th century precipitation means and seasonality. These regimes are used to assess implications for water availability due to concomitant changes in mean and seasonal precipitation and evaporation changes using CMIP5 model future climate projections. Out of 9 regimes, 4 show increased precipitation variation, while 5 show decreased evaporation variation coupled with increasing mean precipitation and evaporation. Increases in projected seasonal precipitation variation in already highly variable precipitation regimes gives rise to a pattern of "seasonally variable regimes becoming more variable". Regimes with low seasonality in precipitation, instead, experience increased wet season precipitation.