A University of California, Berkeley study has come as a surprise to most urban residents. Environmental scientists found that suburbs, which account for less than half of the nation's population, are responsible for about 50 percent of all greenhouse gas emissions, largely carbon dioxide.

"Metropolitan areas look like carbon footprint hurricanes, with dark green, low-carbon urban cores surrounded by red, high-carbon suburbs," Christopher Jones, a doctoral student, said in a statement. "Unfortunately, while the most populous metropolitan areas tend to have the lowest carbon footprint centers, they also tend to have the most extensive high carbon footprint suburbs."        

For the study, the researchers examined 31,000 post codes in all 50 U.S. states. They found that carbon footprints per suburbanite were worse than smaller metro areas

Generally city dwellers are blamed for contributing to greenhouse gas emissions compared to the suburbs as they are more crowded, have lesser green space per person, and there are more emissions from traffic, heating and energy appliances throughout the day.

The reason why carbon footprints are less in cities is because majority of the residences live in flats and use public transport even for short journeys rather than driving. Suburbs are dominated by emissions from cars, trucks and other forms of transportation.

The factors fuelling the greenhouse gas emissions in large metropolitan areas are household income, vehicle ownership and home size.

For example, rich suburban families are more likely to have cars, bigger homes and higher usage of  electronic devices for heating and lightening.

Researchers said that large, population-dense urban cities contribute less greenhouse gas emissions per person than other areas of the country. But these climate benefits are soon nullified by the suburbs.

"The goal of the project is to help cities better understand the primary drivers of household carbon footprints in each location. We hope cities will use this information to begin to create highly tailored, community-scale climate action plans," Daniel Kammen, Professor of Energy, said.

"Cities need information on which actions have the highest potential to reduce greenhouse gas emissions in their communities. There is no one-size-fits-all solution."

The study has been published in the journal Environmental Science & Technology.