Recent theoretical and observational work shows that the
Reynolds stresses due to large-scale extratropical eddies play
a key role in determining Hadley cell strength. This implies
that errors in the representation of extratropical eddies in
climate models could force a bias in the tropical circulation.
Here, this hypothesis is assessed using output from 17 cou-
pled climate models, focusing on Northern Hemisphere win-
ter. Inter-model variability in Hadley cell strength, tropical
temperature and tropical humidity is found to be signifi-
cantly correlated with inter-model differences in stationary
eddy stress. Thus, a significant fraction of the tropical cli-
mate bias found in current climate models may be forced
from the extratropics.

Last Updated: 2008-08-21