Vegetation forcing modulates global land monsoon and water resources in a CO2-enriched climate.

The global monsoon is characterised by transitions between pronounced dry and wet seasons, affecting food security for two-thirds of the world's population. Rising atmospheric CO₂ influences the terrestrial hydrological cycle through climate-radiative and vegetation-physiological forcings. How these two forcings affect the seasonal intensity and characteristics of monsoonal precipitation and runoff is poorly understood. Here we use four Earth System Models to show that in a CO₂-enriched climate, radiative forcing changes drive annual precipitation increases for most monsoon regions. Further, vegetation feedbacks substantially affect annual precipitation in North and South America and Australia monsoon regions. In the dry season, runoff increases over most monsoon regions, due to stomatal closure-driven evapotranspiration reductions and associated atmospheric circulation change. Our results imply that flood risks may amplify in the wet season. However, the lengthening of the monsoon rainfall season and reduced evapotranspiration will shorten the water resources scarcity period for most monsoon regions. Monsoon systems have strong impacts on precipitation and food security over large areas of the world. Here, the authors show that plant responses to rising CO₂ concentrations in the atmosphere play a key role in modulating seasonal rainfall and water resources over global land monsoon regions. [ABSTRACT FROM AUTHOR]