HR: 11:00h
AN: A22A-02    [Abstracts]
TI: The great 20th Century drying of Africa
AU: * Hurrell, J W
EM: jhurrell@ucar.edu
AF: National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307-3000 United States
AU: Hoerling, M P
EM: martin.hoerling@noaa.gov
AF: NOAA, Climate Diagnostics Center, NOAA, R/CDC1 325 Broadway, Boulder, CO 80305-3328 United States
AB: In concert with widespread African surface warming since 1950, a drying trend has been observed, most infamously over the Sahel during July-September, but also following the march of monsoon rains into southern Africa during December-April. The nature and causes for these 1950-1999 downward trends in both northern and southern African summer monsoon rainfall are diagnosed. They are found to be attributable to the atmosphere's response to observed global sea surface temperature variations of the last half-century. Every member of 80 atmospheric climate simulations, forced by the observed ocean history since 1950, yields an African drying trend. Analysis of coupled ocean-atmosphere climate simulations suggests that these drying trends are detectable and distinguishable from natural coupled ocean-atmospheric variations. Yet, neither northern nor southern African drying trends during 1950-1999 are found to occur in greenhouse gas forced coupled ocean-atmosphere simulations. An explanation for the observed 20th Century drying trends is offered, and the role of regional oceanic changes including their relation to greenhouse gas influences, is assessed.
UR: http://www.cgd.ucar.edu/~jhurrell/press.html
DE: 1600 GLOBAL CHANGE (New category)
DE: 1620 Climate dynamics (3309)
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly