Little research has been done about what cities could or should do con
cerning potential global warming. A few cities have adopted programs t
o deal with impacts they perceive may occur, and a worldwide network o
f 100 cities involved with CO2 reduction has recently emerged. Global
warming is a new issue for cities and most are only dimly aware of how
it may affect them. Toronto, through the efforts of a few leaders, ha
s become a pioneer in the development of an urban response program to
global warming. It has charged a city agency to deal with global warmi
ng issues, in particular emissions reduction. Chicago is aware of the
issue and is concerned about the negative impacts global warming could
produce. While behind Toronto, Chicago is moving forward in a number
of areas. These two cities illuminate the policy-making process for gl
obal warming at the urban level and the role 'policy entrepreneurs' ca
n play at this level. In comparing the two cities, a common model of p
olicy development is utilized.