Negative CO2 emissions mitigate extremes of the terrestrial hydrological cycle via a vegetation physiological feedback

Abstract

Negative carbon emissions are certainly executed to mitigate global warming, including minimizing the detrimental effects of weather extremes in the future. Here we show that successful implementation of negative emissions significantly increases terrestrial precipitation. Although CO2 concentrations are reduced by negative emissions, total terrestrial precipitation exceeds ~ 70% more than for periods of the highest CO2 concentrations, when the atmosphere retains more moisture due to increased air temperatures. The physiological processes of terrestrial vegetation are found to play a critical role in this enhanced terrestrial precipitation and hydrological cycle. We found stomatal feedback-enhanced transpiration leads to increases in precipitation, which in turn increases vegetation growth and resultant transpiration, suggesting positive feedback in the hydrological cycle. Furthermore, despite the increase in total precipitation over land, the occurrences of extreme heavy rainfall events and droughts are significantly reduced globally, implying improved water availability and reduced damages from hydrological extremes in the negative emissions scenario.