This is a topic I've been thinking about alot recently. Global warming researchers seem to focus exclusively on CO2 concentrations. Few people are talking about localized warming due to the effects of all this tar, asphalt and concrete. It seems to me that in addition to sequestering CO2, planting trees and other greenery would do a great deal to offset localized warming.
According to the Washington Post:
"Since Daley began investing tax dollars in greening the city, Chicago has planted as many as 400,000 trees, according to city spokesmen. It employs more arborists than any city in the country. There are 2.5 million square feet of green roofs completed or under construction, boosted by expedited permitting and density bonuses for developers who embrace the concept."
You can read the full article here