"In the summer of 2002, [Stuart] Gaffin [of Earth Institute at Columbia University] and his colleagues used satellite temperature data, city-wide land cover maps, and weather data, along with a regional climate model to identify the best strategies for cooling the city. The team estimated how much cooling the city could achieve by planting trees, replacing dark surfaces with lighter ones, and installing vegetation-covered 'green roofs.'
The team studied the city as a whole, as well as six 'hotspot' areasâ€"including parts of Manhattan, the Bronx, Queens, and Brooklynâ€"where air temperatures near the ground were higher than the city-wide average. Each area was serviced by Con Edison, the local power company, so the scientists could compare electricity use. Each area also had available space so that the mitigation strategies the team considered could be modeled in the study and potentially implemented later on.
[...]Gaffin and his colleagues tested the model results against observed temperature and weather conditions in New York City to ensure its predictions were accurate. Then they ran the model assuming different conditions, such as a conversion of all of the cityâ€™s available roof area to light-reflecting surfaces. The model predicted that a combination of urban forestry and light roofs could reduce New York Cityâ€™s overall temperature by 0.67 degrees Celsius (1.2 degrees Fahrenheit) throughout the day."