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 . Programs already under way in New York , Los Angeles and other cities to plant millions of trees can measurably cool the air and dampen the extremity of heat waves over time . Comment: 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 . Comment: He urges planting greenery , making city surfaces reflective , better transit systems .