Global warming: No urban myth.

Climatologists have long recognized that global temperatures are rising, but some skeptics argue that urban sprawl has created the appearance of warming where none has truly happened. A team of researchers has now dismissed that critique.

Meteorologists are concerned about urbanization because rampant development has surrounded some formerly rural weather stations. As heat-trapping concrete replaces vegetation, temperatures tend to rise at these sites.

Thomas C. Peterson of the National Climatic Data Center in Asheville, N.C., and his coworkers weeded out the urbanization effect. Of the 7,280 stations in a global weather network, they examined measurements made at the 2,290 sites that have clearly remained rural. The average temperatures at these stations increased by 0.8 [degrees] C since 1880, nearly the same upswing recorded by urban and rural stations combined, Peterson's team reports in the Feb. 1 GEOPHYSICAL RESEARCH LETTERS.