Mayor Richard M. Daley has announced a plan to dramatically slash emissions of heat-trapping gases, part of an effort to fight global warming and become one of the greenest cities in the nation.

The plan calls for reducing greenhouse gas emissions to three-fourths of 1990 levels by 2020 through more energy-efficient buildings, using clean and renewable energy sources, improving transportation and reducing industrial pollution.

'We can't solve the world's climate change problem in Chicago, but we can do our part,' said Daley on Thursday. 'We have a shared responsibility to protect our planet.'