Global warming model agreement in tropical drying trends
J.D. Neelin et al. evaluate anthropogenic changes in tropical rainfall in
a multimodel ensemble of global warming simulations and find substantial
intermodel agreement on a number of measures, especially drying trends.
The authors examined tropical precipitation response in the latest
simulations under the Intergovernmental Panel on Climate Change (IPCC)
Special Report on Emissions Scenarios (SRES) A2 scenario for anthropogenic
forcings. The results agreed on the overall amplitude of tropical
precipitation decreases in certain areas along the margins of convection
zones, with percent error bars of magnitude similar to those for tropical
warming. They also agreed on increases within the convection zones, with
amplitude increasing with warming. The drying trends outside the
convection zones are likely to be concentration in particular regions,
especially the Caribbean/Central-American region. Land station data since
about 1950 show a significant summer drying trend in the range of 5 - 30%
of the mean rainfall per 100 yr, while satellite data since 1979 show a
slightly larger trend. Attribution of this trend to anthropogenic effects,
however, should be regarded as plausible but still uncertain, the authors
say.