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Cities emit 60 percent more carbon than expected, says study

Metro areas are outsourcing pollution. But a new analysis is already inspiring new progress in cutting emissions


Cities may have been overlooking the true extent of urban pollution, according to a new research paper that shows metro areas are responsible for 60 percent more carbon emissions than previously expected.

But while that’s not great news for those working to limit the impact of climate change, the new information has already helped some local leaders reshape environmental policy to achieve better results.

In short, pollution is being outsourced. The study, Consumption-based GHG emissions of C40 cities, recalculated urban carbon emissions based on both production and consumption. Funded by C40, an international coalition of cities seeking to fight climate change and promote better environmental policy, the analysis found the carbon footprint of big cities was larger than previously estimated, when all the products and services a city uses are included.

Current conventional wisdom estimates cities emit 70 percent of the world’s carbon dioxide, according to National Geographic. But that figure undercounts all the carbon emissions required to sustain the economic activity of cities. The report author Michael Doust included all services, agricultural production, and manufacturing emissions that create the goods used by city dwellers.

The report points out the difference between “consumer” cities such as New York and Paris, which have shrunken industrial sectors and lower local emissions, and “producer cities” in high manufacturing regions such as southeast Asia, which generate a lot of local pollution creating goods used elsewhere. This new calculus also showcases the value of local purchasing and food production. For instance, Cleveland, a leader in local food production, looks much better compared to other American cities when consumption emissions are factored into play.

Many cities have recently enacted policies to cut emissions, including switching to renewable energy, pursuing green energy and resilient design, and designate emissions-free zones. This new C40 report suggests those programs alone aren’t enough.

Mark Watts, executive director of C40 Cities, noted that global carbon emissions have increased 60 percent since 1997. “Using more renewable energy and mass transit won’t be enough to reverse this,” he told National Geographic. “We have to reduce our consumption.”

By providing a more accurate and fair reckoning of the pollution generated by large cities, the report has already inspired planners and politicians to push for programs that take this new data into account.

The report points to strategies that can be used to cut consumption emissions, including smarter purchasing, buying local, and reducing waste. Food policy can make a big difference. Cities can also focus more on retrofitting older building to conserve power.

The city of Paris, for example, has used consumption pollution data to revamp its tourist promotions to focus on marketing to cities accessible by train. It’s also promoting vegetarian diets, as opposed to meat-heavy meals that require relatively high carbon emissions. Stockholm has also created a program that requires developers to examine the embedded carbon in construction materials, leading to wiser decisions about material choices in new developments.