Contribution of climatic changes in mean and variability to monthly temperature and precipitation extremes

Karin Van Der Wiel,Richard Bintanja

doi:10.1038/s43247-020-00077-4

Abstract

The frequency of climate extremes will change in response to shifts in both mean climate and climate variability. These individual contributions, and thus the fundamental mechanisms behind changes in climate extremes, remain largely unknown. Here we apply the probability ratio concept in large-ensemble climate simulations to attribute changes in extreme events to either changes in mean climate or climate variability. We show that increased occurrence of monthly high-temperature events is governed by a warming mean climate. In contrast, future changes in monthly heavy-precipitation events depend to a considerable degree on trends in climate variability. Spatial variations are substantial however, highlighting the relevance of regional processes. The contributions of mean and variability to the probability ratio are largely independent of event threshold, magnitude of warming and climate model. Hence projections of temperature extremes are more robust than those of precipitation extremes, since the mean climate is better understood than climate variability.

Highlights

The frequency of climate extremes will change in response to shifts in both mean climate and climate variability
Future changes in the probability of extreme monthly high-temperature and heavy-precipitation events exceeding the 98th percentile in the present-day climate will be substantial (Fig. 2)
It is shown that future changes in monthly high-temperature extremes are mostly driven by increasing mean temperatures, whereas changes in monthly high-precipitation events depend considerably on changes in precipitation variability

Summary

Introduction

The frequency of climate extremes will change in response to shifts in both mean climate and climate variability. The individual contributions to the occurrence of hightemperature events are of opposite sign, the total effect of climate change on high-temperature event frequency depends on the balance between the two mechanisms Another example concerns Arctic precipitation, for which mean changes are driven mainly by sea ice retreat and surface evaporation[23], whereas changes in variability are governed by atmospheric poleward moisture transport[17]. Even though both are projected to increase as a result of climate change, and contribute to more and more extreme heavy-precipitation events, the mechanisms behind enhanced Arctic downpours crucially depend on the relative importance of increases in mean precipitation and in precipitation variability. The novel split of PR into its mean and variability components will yield valuable insight into the regionally-dependent climate mechanisms that govern changes in extreme climate events

Methods

Results

Conclusion