Study Examines Climate Change in Major U.S. Cities

Research and risk management service firm WeatherBill recently released a climate change study highlighting temperature changes across 130 U.S. cities, in 42 states, each with a population of at least 100,000.

To reach its climatological conclusions, researchers analyzed 30 years of historical weather data from the National Weather Service weather stations in these larger U.S. cities to determine trends in daily average temperature.

The study finds 57% of the cities show increasing winter temperatures, especially in the Midwest. The average annual winter temperature increase across all 130 cities is .08 degrees, which would amount to 2.4 degrees F increase over thirty years.

During the winter (November-February) 74 of the 130 cities show increasing temperatures, while only 2 cities, Los Angeles and San Diego, show decreasing temperatures. Fifty-four cities show no change in winter temperature. Increases are most prevalent in Texas, Oklahoma, Louisiana, Arkansas and in the Midwest. Eight Midwestern cities, including Minneapolis, Chicago, Milwaukee and Omaha show at least a 0.2 degree increase annually, which adds up to 6 degrees over a thirty year period. Temperature increases are noted in all U.S. regions except the Pacific.

Changing temperature trends are far less prevalent in the summer (June-September) when 85% of the cities analyzed show no change in temperature.

Only 17 cities show increasing summer temperatures, most notably in New England. Boise, Hartford, Detroit and Las Vegas are seeing summer temperature increases of at least .09 degree, which adds up to a 2.7 degree increase over thirty years. Reno is increasing .23 degrees F in the summer, which would amount to 6.9 degrees over thirty years. Two cities show decreasing summer temperatures: San Diego and Hampton, Virginia.

Ten cities show increasing temperature trends in both winter and summer, including Boise, Hartford, Detroit and Philadelphia. San Diego is the only city with decreasing temperatures in winter and summer.

A free copy of the study can be downloaded at http://www.weatherbill.com/reports/temptrends.

Business owners can also use the free tools at http://www.weatherbill.com/tools