A new study challenges the idea that rich cities must always churn out more carbon.

Two urban planners and an engineer assessed the carbon emissions of more than 100 cities in 33 countries, with emissions ranging from 0.08 metric tons of carbon dioxide equivalent to 29.8 metric tons.

The study challenges a common argument in the climate policy world: Efficiency must come at the expense of quality of life.

Well-governed cities can have much-reduced greenhouse gas emissions," said David Satterthwaite, a senior fellow at the United Kingdom-based International Institute for Environment and Development, one of the publishers of the study.

Take Porto Alegre, a city in southern Brazil known for its smart growth strategies. The per capita footprint for its residents is 1.48 metric tons of carbon dioxide equivalent, approximately one-eighth of the emissions of Cape Town, South Africa, residents, whose GDP per capita is only slightly higher than that of Porto Alegre.

And although the GDP of Tokyo is slightly higher than Canada, its residents are 5.6 times more efficient.

"Cities can have low greenhouse gas emissions per person and be a nice place to live and work, with a strong economy," said Satterthwaite.

As a baseline, the authors factored in the population, GDP and greenhouse gas emissions of the C40 -- a group of 40 cities that has pledged to flight climate change. If the C40 were a country, it would have the second-highest GDP in the world, the fourth largest population and be the fourth largest greenhouse gas emitter.

Smart planning, lack of resources, or luck
Traditionally, cities have taken a double helping of blame for their emissions. Residents both produce emissions from vehicles, home utilities and waste, but also bear the burden of responsibility for emissions from agriculture, forestry and fossil fuel energy production.

The International Energy Agency (IEA) estimates that urban areas account for more than 71 percent of energy-related emissions, a number that is expected to rise to 76 percent by 2030.

While many of the results can be attributed to smart planning or lack of resources to burn, some cities are just plain lucky.

Compare New York City and Denver: Residents of the nation's most populous city in America emit half the amount of Mile-High residents -- 10.5 metric tons of carbon dioxide equivalent versus 21.5 metric tons.

"Some cities don't have the luxury of deciding where they are [located]," said Daniel Hoornweg, one of the study's authors and lead urban specialist at the World Bank. "Denver has high energy use, its electricity comes from coal, it's spread out, and it's cold."

As one of the largest investors in development projects in the world, the World Bank will be able to use this study as a basis for development aid, along with information on renewable energy use, investment in public transportation and efficiency throughout the power distribution grid, said Hoornweg.

The study is published in the journal Environment and Urbanization on the opening day of the World Economic Forum in Davos, Switzerland, where energy efficiency and resource conservation will be major themes.

"It wouldn't surprise me if it came up in Davos," said Satterthwaite, who will discuss the study at the Intergovernmental Panel on Climate Change's working group meeting in March in Calcutta, India.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500