Anyone who has ever spent a summer in a city knows the pain of the heat island effect. Buildings and roads absorb heat and sunlight and emit it as heat at night, causing temperatures to soar as much as 22 additional degrees. Well, according to new research, climate change will make this an economic hardship for most cities, costing them up to 10.9 percent of their gross domestic products. That’s compared to 5.6 percent for rural economies. The costs come from spending more on cooling plus worker health effects from decreased air and water quality. Installing “cool” pavements and roofs, the authors say, could help reduce those costs — not to mention the risks.