New study shows cities have double the carbon footprint previously thought; one from within their borders, and an equally sized one from supply chains

The carbon footprint of many cities may be larger than initially thought. Researchers from the Potsdam Institute for Climate Impact Research have found that upstream emissions — defined as “emissions that occur along the global production chain of the goods and services purchased by local consumers” — are on the same level as the greenhouse gases directly produced by the cities themselves.

“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,” elaborated lead author Peter-Paul Richler.

To come to this conclusion, the researchers focused on New York City, New York, U.S.A; Berlin, Germany; Delhi, India; and Mexico City, Mexico. They then compared the greenhouse gas emissions from household consumption to each country’s territorial emissions from every source. Through this, the researchers discovered that the upstream emissions generated by each city exceeded their territorial emissions. New York, for example, was reported to have 9.7 tons of carbon dioxide equivalents for its territorial emissions, while the upstream emissions came to 10.6 tons of carbon dioxide equivalents.

Moreover, the upstream emissions were found to have international effects too. According to Science Daily, well over half of Berlin’s upstream emissions were being produced outside of Germany and largely in China, Russia, and other parts of the European Union. On the other hand, the researchers found that 20 percent of Mexico City’s emissions were being generated largely in China and the United States.


In addition to contributing to upstream emissions, the researchers noted that housing and transportation influenced territorial emissions as well. “The average shares across the four cities are 28 percent for housing, 23 percent for transport, 26 percent for food, and 24 percent for all other sectors. Thus, housing and transport contribute over 50 percent to the upstream emissions from household consumption,” wrote the researchers.

They further elaborated by adding that the upstream emissions from each category included factors like electricity generation, solid waste treatment, emissions produced by visits to restaurants, and the transportation, refining, and extraction of gasoline. (Related: Switching from cars to public transportation could save the world $100 trillion and reduce pollution by 40%.)

Following their results, the authors have put out several suggestions to cut down on upstream emissions. These included:

  • Changing building regulations to encourage the use of low-carbon materials in lieu of the likes of steel and cement;
  • Improving the standards of insulation to minimize the need for air conditioning and heating, and possibly reducing the demand for coal-fired power plants;
  • Decreasing car production by upgrading public transportation and by promoting walking and cycling; and
  • Opting for wind or solar power to help subway and bus networks run.

The researchers have stressed the importance of local government involvement, as housing and transportation lie in the policy domain of local officials. “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. “The planned emission reductions presented so far by national governments at the UN summit are clearly insufficient to limit global warming to well below two degrees Celsius, the target agreed by 190 countries, therefore additional efforts are needed.”

Helga Weisz, senior author of the study, added: “The power of cities, open interconnected systems of great density, to tackle climate change even in times of uncertainty on the national and international level has been underestimated by both many local decision-makers and most of the international community. Cities must be encouraged and enabled to focus on their full emission spectrum — local and upstream — as they continue to develop their climate mitigation plans.”

Pichler was quoted in saying: “It’s not the stuff people buy — it’s really housing and transport, and those two topics are really very much in the policy domain of local mayors.” And though housing and transportation can be blamed for the overabundance of direct and indirect emissions, Pichler stated that “it might be easier than mayors think to do something about them.

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