By way of Signal vs. Noise there are many articles featuring Chicago in "green cities" articles including Metropolis and NPR. One thing not mentioned is that there is a "green exhibit" going on at 224 S. Michigan Avenue in the Santa Fe bulding.
Mayor Daley?s Green Crusade | Metropolis Magazine | July 2004
NPR — 'Green' Roofs Sprout Up All Over
roofmeadow.com — a review of the Chicago project and other rooftop projects.
cityofchicago.org — : Chicago City Hall Rooftop garden (City of Chicago's official web site). Also, an explanation of Urban Heat Islands.