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SEAS Colloquium in Climate Science (SCiCS)

Thursday, November 1, 2012 - 2:45pm - 3:45pm
Columbia University, Morningside Campus, Room 214 S.W. Mudd

John Fyfe, Canadian Centre for Climate Modelling and Analysis

"Greenhouse gas, aerosol and ozone forcing of observed Southern Hemisphere precipitation trends"

Observations of extratropical Southern Hemisphere austral summer precipitation over recent decades show mid-latitude drying and high-latitude moistening. Here we show that the observed precipitation trends in two datasets are inconsistent with simulated internal variability, but are closely consistent with trends simulated in response to historical changes in anthropogenic and natural forcings. Simulations with individual anthropogenic and natural forcings suggest that the observed pattern of precipitation change is substantially forced by anthropogenic greenhouse gas and ozone changes, with an opposing influence from aerosols. Our results demonstrate that human influence had a significant impact on precipitation across the mid and high latitudes of the Southern Hemisphere, changes which are expected to have a profound impact on Southern Ocean stratification and hence on ocean-atmosphere heat and carbon fluxes.

John Fyfe is a Senior Scientist with Environment Canada and an Adjunct Professor with the School of Earth and Ocean Sciences at the University of Victoria. He completed his PhD at McGill University and Postdoctoral Fellowship at Princeton University before joining Environment Canada in 1992. John Fyfe's areas of expertise are in large-scale atmospheric and ocean dynamics specializing in polar climate variability and change. He has been a Lead Author and is a Review Editor of IPCC Fourth and Fifth Assessment Reports, respectively.

Host: Lorenzo Polvani