Blame their big houses and outsized driving habits.
North American cities are producing substantially less wealth per ton of greenhouse gas emissions than their European counterparts.
It's not easy to compare them, but we're giving it a shot.
Freakonomics revives a tried, and tired, debate.
Researchers at Arizona State University have created software that tracks carbon dioxide emissions of whole cities, down to individual buildings and roadways.
Mayors have direct control of 75 percent of emission sources in their cities, according to a new report.
The French biochemist behind this strange green light sees it having a "massive" palliative effect on global warming.
Denser, more populous cities are more energy efficient than their smaller counterparts.
A new study finds citywide plans are not as effective as smaller-scale initiatives.
Experts are working on models that would bring green-routing to your GPS