Nov 16, 2015

Anthropogenic Weakening of the Tropical Circulation: The Relative Roles of Direct CO2 Forcing and Sea Surface Temperature Change

by
Jie He and Brian Soden
,
AMS Journal of Climate
  • States there is a lack of consensus on the physical mechanisms that drive the anthropogenic weakening of tropical circulation
  • Investigates the relative roles of direct CO2 forcing, mean SST warming, and the pattern of SST change on the weakening of the tropical circulation using an ensemble of AMIP and aquaplanet simulations
  • Finds that the anthropogenic weakening of the Walker circulation is mostly driven by the mean SST warming
  • Finds increasing CO2 strengthens the Walker circulation through its indirect effect on land–sea warming contrast
  • Finds a weakening caused by the mean SST warming also dominates changes in the Hadley circulation in the AMIP simulations
  • Finds, however, this weakening is not simulated in the Southern Hemisphere in coupled simulations