Frequency : Number of heat-wave days in Atlanta cities has doubled the dog days of summer . Raleigh says greenhouse effect , loss of trees and grass in cityscape are to blame . Brian Stone of heat waves in cities a significant public health threat , he writes . He urges planting greenery , making city surfaces reflective , better transit systems .
Brian Stone : Number of heat-wave days in U.S. cities has doubled since 1950s . Stone says greenhouse effect , loss of trees and grass in cityscape are to blame . Frequency of heat waves in cities a significant public health threat , he writes . He urges planting greenery , making city surfaces reflective , better transit systems .