OOS 11-8 – Forest response to rising CO₂ drives zonally asymmetric rainfall change over tropical continents

Authors

Gabriel J. Kooperman

University of California Irvine

Yang Chen

University of California Irvine

Forrest M. Hoffman (forrest at climatemodeling dot org)

Oak Ridge National Laboratory

Charles D. Koven

Lawrence Berkeley National Laboratory

Keith Lindsay

National Center for Atmospheric Research

Michael S. Pritchard

University of California Irvine

Abigail L. S. Swann

University of Washington

James T. Randerson

University of California Irvine

Session

Ecoclimate Teleconnections: Global Connectivity Between Ecosystems with Consequences for Biodiversity, Material Cycling, and Ecosystem Services in a Changing World
Tuesday, August 8, 2017 10:30 am–10:50 am
Portland Ballroom 258, Oregon Convention Center

Abstract

Background/Question/Methods

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.