Wealthy cities, not just big cities, are the biggest contributors to climate change according to a recent study from the International Institute for Environment and Development.

New York, 26 Jan 2011. According to a new report from the International Institute for Environment and Development (IIED), policymakers need to take a fresh look at the differences in greenhouse gas emissions from different cities.

The study, published in the peer-reviewed journal Environment and Urbanization published by Sage Publications and the IIED shows how to identify new opportunities that could help mitigate climate change. It provides greenhouse gas emission benchmarks for over 100 cities in 33 countries, and suggests policy tools that city governments can use help on climate change.

“Cities worldwide are blamed for most greenhouse gas emissions but many cities have very low emissions, as do many city dwellers - in even the most industrialised countries,” says lead author Daniel Hoornweg, lead urban specialist on Cities and Climate Change at the World Bank.

Differences in production and consumption patterns between cities and citizens mean that it is not helpful to attribute emissions to cities as a whole, asserts Hoornweg. “Policymakers need a better understanding of the sources of emissions if they are to develop real solutions,” he says.

Hoornweg and his colleagues showed that emissions per person per year can vary from as much as 15-30 tonnes of CO2 equivalent in some industrialised to less than half a tonne per person per year in some South Asian cities.

But the report found there are also significant variations within the same countries, and sometimes even within a single city. In the United States, emissions per person in Denver are double those of people in New York, which has a greater population density and a much lower reliance on private vehicles for commuting and travelling – which indicates the advantage of public transport.

In Toronto, residential emissions per person in a densely populated inner city area with high quality public transport were measured at just 1.3 tonnes of CO2 equivalent, compared to 13 tonnes in a sprawling suburb of the same city.

There are also some surprising differences between cities in different parts of the world. For example, many European cities have less than half the emissions per person of many cities in North America, and some relatively wealthy cities in Brazil have lower emissions per person than poorer cities in Asia and Africa. Even more surprising, emissions per person in London are lower than those in Cape Town, South Africa.

“Lifestyles and consumption patterns are key drivers of greenhouse gas emissions,” says Hoornweg.  In the case of Western cities that have continuous high consumer demand for Chinese goods, the overall emissions will be high even though the CO2 output from the local people is relatively low. “From the production perspective Shanghai has high emissions but from the consumption perspective its emissions are much lower (than some Western cities),” he adds.

Equally, a wealthy city where many inhabitants have a high-consumption lifestyle can have low per capita emissions, but very high contributions from a consumption perspective. This, says the study, shows that it is the world’s wealthiest cities and their wealthiest inhabitants that cause unsustainable levels of greenhouse gas emissions, not cities in general.

“This paper reminds us that (this is the case),” says Dr David Satterthwaite, editor of the Environment and Urbanization study and a senior fellow at IIED. “Most cities in Africa, Asia and Latin America have low emissions per person,” he points out. “The challenge for them is to keep these emissions low even as their wealth grows.”

The paper is available online at http://eau.sagepub.com/content/early/recent or by emailing mike.shanahan@iied.org