Cities can cut carbon emissions beyond urban borders: study

Cities can cut greenhouse gas emissions far beyond their urban borders, according to a study that calculated the first internationally comparable carbon footprints for four cities, including Delhi.
Greenhouse gas emissions caused by urban households' purchases of goods and services from beyond city limits are much bigger than previously thought, according to researchers at Potsdam Institute for Climate Impact Research (PIK) in Germany.
These upstream emissions may occur anywhere in the world and are roughly equal in size to the total emissions originating from a city's own territory, they said.
The study offers local policy-makers more leverage to tackle climate change, in view of the UN climate summit COP23, researchers said.

They calculated the first internationally comparable greenhouse gas footprints for four cities from developed and developing countries: Berlin, New York, Mexico City and Delhi.
Contrary to the common belief, consumer goods like computers or sneakers that people buy are not most relevant, but housing and transport - sectors that cities can substantially govern.

"It turns out that the same activities that cause most local emissions of urban households - housing and transport - are also responsible for the majority of upstream emissions elsewhere along the supply chain," said Peter-Paul Pichler from PIK.
"People often think that mayors cannot do much about climate change since their power is restricted to city limits, but their actions can have far-reaching impacts," said Pichler, lead-author of the study.

While the greenhouse gas footprint in the four cities that the scientists scrutinised range from 1.9 tonnes in Delhi to 10.6 tonnes in New York of CO2 equivalent per person and year, the proportions of local to upstream household emissions as well as the relative climate relevance of housing and transport turn out to be roughly the same.
The international reach of upstream emissions is vast but varies. In terms of emissions, Berlin's global hinterland is largest, with more than half of its upstream emissions occurring outside of Germany, mostly in Russia, China and across the European Union, researchers said.

Around 20 per cent of Mexico City's considerably smaller upstream emissions occur outside Mexico, mainly in the US and China, they said.