Anthropogenic Contribution to the Southeast Pacific Precipitation Decline and Recent (2010-2015) Mega-Drought in Chile

Abstract:

Within the large uncertainties in the precipitation response to the anthropogenic climate forcing, the projections towards dryer conditions in the southeast Pacific sector and west bound of southern South America represent a particularly robust signature in climate model simulations. A rainfall decline of consistent direction but of larger amplitude than those simulated has been observed in Chile during the last decades, but the causes of this trend have never been formally attributed. With this purpose, we analyze local rain-gauge data and contrast them to a large ensemble both of fully-coupled and sea surface temperature-forced simulations. In concomitance with large-scale circulation changes, we show that the Pacific Decadal Oscillation explains about 50% of the rainfall trend observed since 1979 in central Chile. Our results also indicate that the remaining fraction of the observed drying is unlikely (p < 0.05) to be driven exclusively by natural phenomena, but is consistent with the simulated regional effect of climate change. Given these results, we conclude that the increasing frequency of drought, such as the one that has been affecting central Chile since 2010, emerges as a realistic scenario for this region under the current socio-economic pathway.