Cities will be big players in curbing AGW. They can look for big gains if they play their cards right, and big losses if we fail. Conservation, by clustering people in high-density communities of new buildings using less energy, can replace many current forms of power generation and meet our needs.
It's a challenge, but the modern city has resources no previous cities had, and cities have done pretty well in the past. What aspect of modern life, always excepting the climate itself, is not ten times as fast or strong as what went before? And the 20th century offers plenteous example of the patchwork reconstruction of civilized life by private and government agencies performing iterations of social organizing to provide social welfare for the community and the individual.
Most cities know they won't get much help from their central governments, but they must prepare for the deluge of former suburbanites who will want to move into town, when the full cost of carbon emissions are understood and levied against the users.
Most of the former suburbanites will have suffered ruinous financial losses before giving up and moving into town, and this will be one problem among many in dealing with huge increases in population. Still, for a city, that's a good problem to have. It is, in a sense, the problem they've always solved so well.