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


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


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



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.


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.

Forrest M. Hoffman (forrest at climatemodeling dot org)