City lights may burn bright, but overall the greenhouse gas emissions of large cities are far below those of rural areas, a new report finds.
at the in London, who led the study, says previous claims that cities contribute disproportionately to global climate change are unfounded.
鈥淗istorically, people have associated pollution and environmental damage with cities and, as far as climate warming goes, it is true that urban areas have large energy consumption,鈥� he says. 鈥淏ut many emissions come from rural areas, and methane is a far more potent greenhouse gas than carbon dioxide.鈥�
Advertisement
To discover just how bad city life is for the climate, Dodman compared greenhouse gas emissions in 12 large cities around the world with the average emissions of their respective countries. He found that, on average, city dwellers emit fewer greenhouse gases than the average for their country (see the complete list at bottom).
鈥楥ritical mass鈥�
In terms of per-capita emissions, the most environmentally unfriendly city of those studied is Washington, DC. With 19.7 tonnes of CO2 equivalent per head, the carbon footprint of each citizen there is nearly three times that of other large cities in developed nations. Dodman blames this on the amount of office space in the city. However, residents of DC still emit only 82.4% of the US average.
This holds true for other wealthy cities. Per capita emissions in New York, Toronto and Barcelona are only a third of their national average, and the emissions of Tokyo, London and Seoul come in at about half of their countries鈥� level.
鈥淭here are density-related advantages for both travel and heating,鈥� says Dodman. 鈥淲hen you have a critical mass of people like in London or New York, public transport becomes a feasible option for many, while people in more rural areas rely more on cars. And a flat that is surrounded by others is more efficient to heat than a free-standing house.鈥�
On paper, citizens of the Brazilian cities Rio de Janeiro and Sao Paulo have small carbon footprints, emitting only 28 and 18% of the country鈥檚 average. But according to Dodman, this is 鈥渕ore because the Brazilian national profile is heavily dominated by deforestation and agriculture, not because those cities are doing particularly well鈥�.
Beijing and Shanghai, in contrast, emit more than double China鈥檚 national average, but this most likely results from their thriving manufacturing industries and city boundaries encompassing more rural areas than elsewhere, he says.
鈥極utsourced emissions鈥�
at the Tyndall Centre for Climate Change Research in the UK says that, although dense cities may reduce transport emissions and act as 鈥渉ugely beneficial鈥� hubs of innovation, their total effect on the climate also depends on measures that were not captured by the current analysis.
鈥淐ities where the service sector dominates have outsourced carbon intensive industries to developing countries, yet are still voracious consumers of industrial products,鈥� Hall says. 鈥淭here is a large discrepancy between production-based and consumptions-based metrics of emissions.鈥�
Dodman agrees. 鈥淭he emissions for a pair of shoes made in China and sold in the UK are currently allocated to China, not to [the UK], so it is fair to ask whether we should count emissions according to the location of production or the location that is driving the consumption.鈥�
Dodman also stresses that despite comparing well to their nations鈥� average carbon footprint, western cities have room for plenty of improvement. In the list of top climate offenders, their emissions still dwarf those from cities in developing nations.
Dirty dozen?
The following list shows the greenhouse gas emissions per person in the 12 cities analysed 鈥� in descending order of emissions. The cities were chosen on the basis of good data being available for comparison and to cover Asia, Europe and North and Latin America.
1. Washington, DC, US 鈥� 19.7 tonnes of CO2 equivalent
2. Glasgow, UK 鈥� 8.4 tonnes
3. Toronto, Canada 鈥� 8.2 tonnes
4. Shanghai, China 鈥� 8.1 tonnes
5. New York City, US 鈥� 7.1 tonnes
6. Beijing, China 鈥� 6.9 tonnes
7. London, UK 鈥� 6.2 tonnes
8. Tokyo, Japan 鈥� 4.8 tonnes
9. Seoul, South Korea 鈥� 3.8 tonnes
10. Barcelona, Spain 鈥� 3.4 tonnes
11. Rio de Janeiro, Brazil 鈥� 2.3 tonnes
12. Sao Paulo, Brazil 鈥� 1.5 tonnes
Journal Reference:
