Understanding how anthropogenic CO2 emissions may impact future precipitation is critical for sustainably managing ecosystems, particularly for drought-sensitive tropical forests. While there is much uncertainty about tropical precipitation changes, nearly all models from the Coupled Model Intercomparison Project Phase 5 predict a strengthening zonal precipitation asymmetry by 2100, with increases over Asian and African forests and decreases over lowland South American forests.
Results/Conclusions:
Here we show that the plant physiological response to increasing CO2 is a primary mechanism responsible for this pattern. Using a simulation design in which CO2 increases are isolated over individual continents, we find that contrasting regional circulation and moisture flux anomalies are driven by local decreases in transpiration. These simulations indicate that the sum of local responses over individual continents mostly explains the pan-tropical precipitation asymmetry. Our analysis suggests that forests in South America may be more vulnerable to rising CO2 than forests in Asia or Africa.