The image of cities is often traffic-clogged, polluted and energy-guzzling, but a new study has shown that city dwellers have smaller carbon footprints than national averages.

The report by London-based International Institute for Environment and Development (IIED) looked at 11 major cities on four continents, including London, Tokyo, New York and Rio de Janeiro.

It found per capita greenhouse gas emissions for a Londoner in 2004 were the equivalent of 6.2 tonnes of CO2, compared with 11.19 for the UK average.

The rural northeast of England, Yorkshire and the Humber, were singled out for having the highest footprints per capita in the UK.

In the US, New Yorkers register footprints of 7.1 tonnes each, less than a thrid of the US average of 23.92 tonnes.

The use of public transport and denser housing are two of the reasons for urbanites' comparatively low carbon footprints, the authors said, adding that the design of cities significantly affects their residents' emissions.

"Tokyo has considerably lower emissions per person than either Beijing or Shanghai and this shows clearly that prosperity does not lead inevitably to greater emissions," said report author David Dodman. "Well-designed and well-governed cities can combine high living standards with much lower greenhouse gas emissions."

Greenhouse gas emissions per capita (tonnes of CO2 equivalen). Source: Guardian/IIED

The report coincides with a study published today by the UK's Commission for Architecture and the Built Environment, which called for more spending on parks and trees in cities to create jobs and cut climate change emissions.

The IIED is not the first organisation to suggest city living is greener than living in the countryside: last summer the Brookings Institute said residents in US cities had 14% lower footprints than the US average.

The authors of this new report, however, admit that assessing emissions is not an exact science because different countries and cities employ different methodologies for counting CO2 emissions, making a precise like-for-like comparison difficult.

Most city dwellers' emissions are also still too high to curb climate change, despite being low compared with national averages. "With the exceptions of São Paulo and Rio de Janeiro, all of the cities surveyed already exceed the per capita ﬁgure" needed to keep CO2 levels below 450 parts per million, warned Dodman.