The carbon footprint of some of the world’s biggest cities is 60 percent larger than previously estimated when all the products and services a city consumes are included, according to a new analysis.

The report was released Tuesday at the IPCC Cities and Climate Change Science Conference in Edmonton, Canada, and estimated the carbon emissions for the food, clothing, electronics, air travel, construction materials, and so on consumed by residents but produced outside city limits.

The world’s cities emit 70 percent of the world’s carbon dioxide—and that’s likely higher when consumption emissions are included, says report author Michael Doust, program director at C40 Cities, a network of the world’s cities committed to addressing climate change.

“We’re missing the other side of the coin if we only measure emissions involved in the production of food, energy, or other products and services,” Doust said in an interview in Edmonton. “Knowing what the consumption emissions are and where allows cities and residents to make better decisions on how to reduce their carbon emissions.”

Wealthy "consumer cities" such as London, Paris, New York, Toronto, or Sydney that no longer have large industrial sectors have significantly reduced their local emissions. However, when the emissions associated with their consumption of goods and services are included, these cities’ emissions have grown substantially and are among the highest in the world on a per person basis, the report says. Meanwhile, "producer" cities in India, Pakistan, or Bangladesh generate lots of industrial pollution and carbon emissions in the manufacture of products that will be sold and consumed in Europe and North America.

Climate Change 101 with Bill Nye

The report, Consumption-based GHG emissions of C40 cities, examined the greenhouse gas emissions associated with goods and services consumed by residents of 79 cites in the C40 network, including food, clothing, electronic equipment, air travel, delivery trucks, and construction industries.

“We’re still going in the wrong direction on climate change,” said Mark Watts, executive director of C40 Cities. Global carbon emissions have increased 60 percent since the international 1997 Kyoto agreement to reduce emissions. “Using more renewable energy and mass transit won’t be enough to reverse this,” said Watts. "We have to reduce our consumption.”

“This new research will help city policy makers to better understand the true impact of their city on global climate change, and so play an ever bigger leadership role in delivering climate action,” he added. (Read: Has the U.S. really reached an energy tipping point?)

Outsourcing Pollution?

“What we buy must be part of our efforts to reduce our emissions. We can’t just outsource them to other regions,” said Don Iveson, the mayor of Edmonton. Iveson said consumption-based accounting is key to knowing what a city’s true carbon footprint is. “Smarter purchasing, buying local, and reducing waste are part of what can be done to reduce consumption emissions.”

Matt Gray, the chief of sustainability at the city of Cleveland, Ohio, says he welcomes this new approach. By the old method of accounting, manufacturing cities like Cleveland often rank poorly in current measures of sustainability, he notes. Yet cities with service-based economies that consume the things Cleveland makes rank better. Resource consumption was not a factor in last year’s U.S. Cities Sustainable Development Goals Index, which put Cleveland at the bottom. Yet the fact that Cleveland is widely considered a national leader in local food production wasn’t a factor in the index, Gray said.

In working on this new accounting of consumption emissions, the city of Paris is targeting its tourist promotions to countries where travelers can visit by train, in an effort to reduce emissions from air travel. It’s also encouraging residents to change their diets from carbon-emission-heavy meats to vegetarian fare. Stockholm has asked all of its developers to estimate their embodied emissions in construction materials. Simply looking at the data has already led to decisions to use materials with lower emissions, said Doust. And it is helped in city decisions about retrofitting old buildings or building new ones.