[LONDON] Cities contribute much less to greenhouse gas (GHG) emissions than assumed, particularly in poorer countries, according to a researcher.
Publishing his work in Environment and Urbanization last week (26 September), David Satterthwaite, a senior fellow in human settlements at the UK-based International Institute of Environment and Development, says estimations of the GHG emissions of cities are exaggerated.
He says the figure often used — that cities contribute 75–80 per cent of GHGs — "seems to be one of those figures plucked out of the air. That figure may have been given for the United States and people think it's relevant everywhere."
Satterthwaite used figures from the 2007 UN Intergovernmental Panel on Climate Change report to estimate the contributions of different sectors such as energy supply, agriculture, industry and deforestation to GHG emissions.
He concluded that cities account for 30–40 per cent of total emissions.
"We know that a large proportion of heavy industries aren't in cities, we know that many fossil fuel power stations aren't in cities. And we know that in the rich world, rich, high-consumption households live outside cities — so the [previously estimated] numbers don't make any sense."
Emissions from cities vary from country to country, and there are enormous disparities between cities in developed and developing countries, Satterthwaite told SciDev.Net.
In Brazil, for example, deforestation is a major contributor to GHG emissions, but that is not the case in other countries.
Concrete figures on emissions from most developing country cities are not available, as few have detailed GHG emission inventories. But energy use, lack of industry and the number of automobiles used per person in developing country cities indicate that emissions are 100–1,000 times less than in New York or London, says Satterthwaite.
Allocating GHGs based on production rather than consumption is not useful, he says, and unfairly blaming cities draws attention away from the activities and consumption patterns of high- and middle-income lifestyles that drive emissions.
If cities were allocated GHGs based on consumption, their emissions would increase in rich countries, but would remain low in poor countries.
But this does not mean that cities in developing countries can ignore their levels of GHG emissions.
"In a sense, what you want for developing countries is a very strong focus on adaptation with a little mitigation perspective," says Satterthwaite.
"Tackling climate change by reducing emissions requires knowledge of which activities and sectors — such as burning fossil fuel, deforestation, agriculture — contribute GHGs to the atmosphere. But apportioning such emissions to locations or nations is a socioeconomic exercise," says Chris Jones, a carbon-cycle climate scientist at the Met Office Hadley Centre, United Kingdom.
"GHGs such as carbon dioxide and methane are the primary cause of climate change and are typically well mixed in the atmosphere. The precise location of the release of emissions is not important — the effect on climate will be the same."
Environment & Urbanization 20, 539 (2008)