Precipitation variability increases in a warmer climate

Friday, December 15, 2017 - 08:15
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Precipitation variability connects mean and extreme precipitation. Despite that both mean and extreme precipitation increase in a warming climate, it is often assumed that precipitation variability does not to change with warming, or that precipitation mean and variability change at the same rate. Here, we show that precipitation variability in climate models increases over a majority of global land area in response to warming. Precipitation variability increases over a range of timescales by at least as much as mean precipitation and less than moisture and extreme precipitation, due to an increase in moisture which is partially mitigated by weakening circulation. In the global mean, precipitation variability increases by 3-4 %K-1 (4-5 %K-1 over land) and is remarkably robust on timescales from daily to decadal. We show that changes in daily variability at observing stations are consistent with model simulations. Understanding changes in precipitation variability is essential for a complete explanation of the hydrologic cycle’s response to warming and its impacts. The increase in precipitation variability is a robust emergent aspect of the water cycle that is changing as a result of anthropogenic warming.

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