Climate change study provides greenhouse-gas emissions for 100 cities in 33 nations

Study asks 'whose greenhouse gas is it anyway?' and urges a broader look at cities and climate change  

News, 25 January 2011

Policymakers need to take a fresh look at the differences between greenhouse gas emissions from different cities to identify new opportunities to mitigate climate change, says a forthcoming study in the peer-reviewed journal Environment and Urbanization published by Sage Publications and the International Institute for Environment and Development.

The study provides greenhouse gas emissions for over 100 cities in 33 countries and suggests policy tools that city governments can use to take action 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. Policymakers need a better understanding of the sources of emissions if they are to develop real solutions."

Hoornweg and colleagues showed that emissions per person per year vary from 15-30 tonnes of carbon dioxide equivalent in some cities in industrialised countries to less than half a tonne per person per year in various cities in South Asia.

But there is also great variation within countries and even within cities:

  • In the United States, the emissions per person in Denver are double those of people in New York, which has a greater population density and much lower reliance on private vehicles for commuting.
  • In Toronto, residential emissions per person in a dense, inner city neighbourhood with a high quality public transport system are just 1.3 tonnes of carbon dioxide equivalent, compared to 13 tonnes in a sprawling distant suburb.

And there are some surprising differences between cities in different parts of the world:

  • Many European cities have less than half the emissions per person of many cities in North America
  • Some successful and wealthy cities in Brazil have lower emissions per person than poorer cities in Asia and Africa
  • Emissions per person in London are lower than those in Cape Town, South Africa

The paper shows that emissions vary greatly depending on whether they are calculated according to what a city (or a citizen) produces or instead what they consume.

"Lifestyles and consumption patterns are key drivers of greenhouse gas emissions in emissions in far off cities, as in the case of Western consumer demand for Chinese goods," says Hoornweg. "From the production perspective Shanghai has high emissions but from the consumption perspective its emissions are much lower."

Equally, a wealthy city where many inhabitants have a high-consumption lifestyle can have low per capita emissions from a production perspective, but very high emissions from a consumption perspective.

"This paper reminds us that it is the world's wealthiest cities and their wealthiest inhabitants that cause unsustainable levels of greenhouse gas emissions, not cities in general," says Dr David Satterthwaite, who is the editor of Environment and Urbanization and a senior fellow at the International Institute for Environment and Development.

"Most cities in Africa, Asia and Latin America have low emissions per person. The challenge for them is to keep these emissions low even as their wealth grows."

Notes to editors

The paper provides the greenhouse-gas emissions per person in more than 100 cities in Argentina; Australia; Bangladesh; Belgium; Bhutan; Brazil; Canada; China; Czech Republic; Finland; France; Germany; Greece; India; Italy; Japan; Jordan; Mexico; Nepal; The Netherlands; Norway; Portugal; Republic of Korea; Singapore; Slovenia; South Africa; Spain; Sri Lanka; Sweden; Switzerland; Thailand; United Kingdom; and United States.

Citation: Hoornweg, D., Sugar, L. Trejos Gomez, C.L. 2011. Cities and greenhouse gas emissions: moving forward. Environment and Urbanization. Vol 23(2). doi:10.1177/0956247810392270