1 October 2009

City report: Denver emits most greenhouse gas

Denver, the mile high city, released the largest amount of greenhouse gases (GHG) and Barcelona the smallest amount in a new study documenting how differences in climate, population density, and other factors affect GHG emissions in global cities.

The study identifies ways in which cities can reduce GHG emissions.

Some cities are developing strategies to reduce releases of GHG, which include carbon dioxide, methane, and other gases that can contribute to global warming through the greenhouse effect, said Christopher Kennedy, associate professor at the University of Toronto. Not enough information was previously available on why emissions vary considerably among different cities. The authors asked, “How and why do emissions differ between cities?”

To help answer those questions, scientists analyzed those variations and how climate, power generation, transportation, waste processing, and other factors contributed to the differences.

By including upstream emissions from fuels, the researchers found GHG emissions attributable to cities exceed those from direct end use by up to 24%.

Denver had the highest overall GHG emissions, with levels two to five times higher than other cities. Its high levels were due partly to its high use of electricity, heating and industrial fuels, and ground transportation, they said. Los Angeles was second on the list, followed by Toronto and Cape Town (tied for third), Bangkok, New York, London, Prague, Geneva, and Barcelona.

For related information, go to www.isa.org/environment.