Saving Energy and Improving Air Quality in Urban Heat Islands

Temperatures in urban areas have increased because solar energy is more strongly absorbed by additional roofs and pavements. Downtown Los Angles is now 2.5 Kelvin warmer than in the 1930s, which requires 1–1.5 GWe more electricity to cool buildings on summer days, costing an extra $100 million/year. Cool roof and pavement materials with increased reflectivity of 0.25 can lower surface temperatures by 10 K. If Los Angles urban temperatures could be reduced by 3 K, ozone concentrations could be reduced considerably.