Altered hydrologic feedback in a warming climate introduces a â•œwarming holeâ•š

In the last 25 years of the 20th century most major land regions experienced a summer warming trend, but the central U.S. cooled by 0.2–0.8 K. In contrast most climate projections using GCMs show warming for all continental interiors including North America. We examined this discrepancy by using a regional climate model and found a circulation-precipitation coupling under enhanced greenhouse gas concentrations that occurs on scales too small for current GCMs to resolve well. Results show a local minimum of warming in the central U.S. (a “warming hole”) associated with changes in low-level circulations that lead to replenishment of seasonally depleted soil moisture, thereby increasing late-summer evapotranspiration and suppressing daytime maximum temperatures. These regional-scale feedback processes may partly explain the observed late 20th century temperature trend in the central U.S. and potentially could reduce the magnitude of future greenhouse warming in the region. Disciplines Agriculture | Agronomy and Crop Sciences | Atmospheric Sciences | Climate | Environmental Indicators and Impact Assessment | Hydrology Comments This article is from Geophysical Research Letters 31 (2004): L17109, doi:10.1029/2004GL020528. Posted with permission. Authors Zaitao Pan, Raymond W. Arritt, Eugene S. Takle, William J. Gutowski Jr., Christopher J. Anderson, and Moti Segal This article is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/ge_at_pubs/101 Altered hydrologic feedback in a warming climate introduces a