Big cities like New York, London and Shanghai send less pollution into the atmosphere per capita than places like Denver and Rotterdam, said a study released Tuesday
Researchers examined data from 100 cities in 33 nations for clues about which were the biggest polluters and why, according to the report in the peer-reviewed journal Environment and Urbanization.
While cities across the world were to blame for around 71 percent of the world's greenhouse gas emissions, urban dwellers who can use public transport rather than drive helped to lower per capita emissions in some cities.
For instance, the sprawling western US city of Denver's per capita emissions were nearly double those in New York City, home to eight million inhabitants and a gritty, heavily used subway system.
"This is mainly attributable to New York's greater density and much lower reliance on the automobile for commuting," said the study.