HR: 0800h
AN: A41A-04    [Abstracts]
TI: Intense and Extensive Summer Heat Waves Under Current and Possible Future Climates
AU: * Gershunov, A
EM: sasha@ucsd.edu
AF: Alexander Gershunov, Scripps Institution of Oceanography - 0224, La Jolla, CA 92093, United States
AB: The spatial scale of a heat wave is an important determinant of its impacts. Extensive summer heat waves are considered over Europe and North America in observations and model projections. Recent trends towards more frequent and extensive hot spells follow global warming trends, but are regionally modulated on decadal timescales. Model projections reflect these influences. Europe, warming continuously, had an early warning in 2003 of conditions projected for the second half of the 21st century. Until summer 2006, North America, in spite of a general summer warming, has not seen the extent of heat consistent with model projections. The recent warming over North America is unusual in that it occurred without the large-scale encouragement of a dry soil associated with precipitation deficit. Extensive and persistent heat waves naturally occur in association with widespread drought. Regional precipitation anomalies together with global anthropogenic influences can explain the atypical pattern of North American summer warming prior to 2006. Last summer's widespread heat waves were consistent with drier conditions over the Eastern US. Drought has the potential to seriously exacerbate the recent warming over North America to levels significantly in excess of the 1930s and in line with the warmest projections. Assuming realistic warming scenarios, a long-term anthropogenic increase (decrease) in the frequency and spatial extent of regional hot (cold) spells is projected to be strong and strongly modulated by decadal-scale variability throughout the 21st century.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1626 Global climate models (3337, 4928)
DE: 1630 Impacts of global change (1225)
DE: 1655 Water cycles (1836)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly