Hot spots in Washington show up as red areas in this satellite image. The presence of such heat islands increases energy use and raises smog levels. The largest red patch is at the site of a convention center. The coolest areas (green) are those covered by grass and trees.
Credit: S. Stetson, Global Environmental Management
Urban heat islands are not inevitable, but the product of dark roofs, black pavement, and loss of vegetation. A "cool communities" approach would lower air-conditioning use and make the air healthier.
On a summer afternoon, central Los Angeles registers temperatures typically 5°F higher than the surrounding suburban and rural areas. Hot roofs and pavements, baked by the sun, warm the air blowing over them. The resulting urban "heat island" causes discomfort, hikes air-conditioning bills, and accelerates the formation of smog.
Heat islands are found in many large cities, including Chicago, Washington, and (as the Olympic athletes and fans can attest) Atlanta. The effect is particularly well recognized in cities that quote two airport temperatures on the weather report. Thus Chicago-Midway airport is typically a few degrees hotter than suburban O'Hare, and the same difference applies between Washington National airport and Dulles.
To read the entire article you must log in:
Most of our content — all daily news, blogs, and videos — is free. Magazine stories are paid. To read this story, you must have a subscription or you must use a reading credit. Registration to Technology Review is free and entitles registrants to three free reading credits.
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
Our list of the 50 most innovative companies, including the following:
On Twitter
Become a Fan on Facebook
Subscribe to the Feed