Abstract

Understanding changes in precipitation variability is essential for a complete explanation of the hydrologic cycle’s response to warming and its impacts. While changes in mean and extreme precipitation have been studied intensively, precipitation variability has received less attention, despite its theoretical and practical importance. Here, we show that precipitation variability in most climate models increases over a majority of global land area in response to warming (66% of land has a robust increase in variability of seasonal-mean precipitation). Comparing recent decades to RCP8.5 projections for the end of the 21st century, we find that in the global, multi-model mean, precipitation variability increases 3–4% K−1 globally, 4–5% K−1 over land and 2–4% K−1 over ocean, and is remarkably robust on a range of timescales from daily to decadal. Precipitation variability increases by at least as much as mean precipitation and less than moisture and extreme precipitation for most models, regions, and timescales. We interpret this as being related to an increase in moisture which is partially mitigated by weakening circulation. We show that changes in observed daily variability in station data are consistent with increased variability.

Highlights

  • Precipitation variability is a crucial climatic factor for society, agriculture, and the environment; increased precipitation variability can reduce agricultural yield[1], and in developing countries can affect growth of children[2]

  • Most work in the last decade focused on the robust response of ENSO-related precipitation change across models, which occurs despite disagreement on changes in ENSO-related sea-surface temperature variability[22,23,24,25,26,27]; these studies are all limited to interannual timescales and focused on the tropics

  • To assess whether models predict an increase in interannual precipitation variability with warming, we examine the spatially-aggregated change[29] in the interannual standard deviation of seasonal-mean precipitation

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Summary

Introduction

Precipitation variability is a crucial climatic factor for society, agriculture, and the environment; increased precipitation variability can reduce agricultural yield[1], and in developing countries can affect growth of children[2]. It is sometimes assumed that precipitation variability does not change in a warming climate [e.g., refs4,5], or that mean precipitation and its variability change at the same rate[6]. Early climate model simulations indicated that daily to interannual precipitation variability increases in response to a doubling of carbon dioxide[11,12,13]. Very recent work has focused on changes in precipitation variability at regional scales, including the monsoons[20], and one study has examined decadal prediction and identified increases in interannual precipitation variability[21]. Most work in the last decade focused on the robust response of ENSO-related precipitation change across models, which occurs despite disagreement on changes in ENSO-related sea-surface temperature variability[22,23,24,25,26,27]; these studies are all limited to interannual timescales and focused on the tropics. The changes in precipitation variability are interpreted in the framework for the changing distributions of moisture, vertical velocity, and precipitation presented in ref.[28]

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