Effects of CO2 vegetation forcing on precipitation and heat extremes in China

Abstract Anthropogenic CO2 emissions are expected to significantly impact climate patterns, including extreme heat events. The influence of plants on land-atmosphere water and energy exchanges plays a crucial role in shaping these heat extremes. The response of vegetation growth and physiology to elevated CO2, both directly and indirectly, will determine their contribution to future heat extremes. In this study, we employed a suite of CMIP6 earth system models (ESMs) to differentiate between the effects of radiative forcing and vegetation forcing under elevated CO2 background on extreme heat and precipitation events in China. The changes observed can be attributed to CO2 physiological forcing, which reduces transpiration and its related cooling impact, leading to a decrease in clouds and precipitation under 2×CO2 and 4×CO2 scenarios. Our findings indicate that CO2-induced vegetation forcing (VEG) intensifies the frequency and severity of future heatwaves. Additionally, we found that CO2-driven vegetation decreases extreme precipitation and increases dry days numbers in most humid regions of China, despite the increase in transpiration resulting from the saving of soil moisture and aboveground biomass enhancement due to CO2 fertilization.