Municipal greenhouse gas emissions are 60% higher than city planners assume, after factoring in items that residents consume but are produced outside city limits, according to a study released by C40 Cities during this week’s IPCC Cities and Climate Change Science Conference in Edmonton.
The study covers an array of everyday items, from food and clothing to electronics, construction materials, and air travel, international environment journalist Stephen Leahy reports for National Geographic. It calculates GHG emissions in 79 cities across the C40 network.
While cities are conventionally thought to have control over 60% of global emissions, “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,” said Program Director Michael Doust. “Knowing what the consumption emissions are and where allows cities and residents to make better decisions on how to reduce their carbon emissions.”
[Editor’s note: In the comments below this story, sharp-eyed Energy Mix subscriber Ralph Torrie points out that if cities account for 70% of GHG emissions, and Scope 3 emissions increase that tally by 60%, we end up with cities responsible for 112% of global emissions. If you can shed light on this, please share your own comment!]
The difference plays out in wealthy consumer cities like London, Paris, New York, Toronto, and Sydney “that no longer have large industrial sectors” and “have significantly reduced their local emissions,” National Geographic notes. “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.”
By contrast, “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.”
Meanwhile, a study published this week in the Proceedings of the National Academy of Sciences tracks the greenhouse gas emissions that resulted from suburban expansion southwest of Salt Lake City, Utah, and compares those results to population growth in the city centre. “It’s the latest evidence highlighting the environmental consequences of suburban expansion, often accompanied by more miles driven by cars and larger free-standing homes that require more energy for heating and cooling,” the Washington Post reports.
With urban planning becoming a focal point as many cities move into the lead on climate action, the PNAS study points to a “contentious and complicated” debate that could arise around urban growth, the Post notes. The suburban region highlighted in the study “contains a noteworthy community called Daybreak that was itself built around energy-efficient homes and walkability, and heralded for its design by the Urban Land Institute—precisely what climate advocates would seem to want to see more of.”
And yet, “if you put more people where there weren’t people before, you’re going to have more emissions,” said UC Berkeley researcher Christopher Jones, head of the CoolClimate Network, a U.S. carbon footprinting organization. “The question is putting them in one type of development, compared with somewhere else.”
“It’s urban expansion. You’re taking the land surface to a suburban development where there’s cars and houses and some industry, and CO2 emissions go up,” agreed lead author Logan Mitchell of the University of Utah. “In some ways it’s not so surprising, but it’s neat to have measured it and see that response in the atmosphere.”
He added that the differences between suburban and downtown emissions probably had a lot to do with personal transportation.
“Urban population growth doesn’t necessarily mean more cars on the road, given the fact that people are moving close to the city centre and have public transport, walking, and biking options,” the Post states. “Suburban growth also tends to result in larger homes that require more energy to heat, and if that is provided by natural gas burning at the site of the home, then this, too, would lead to more emissions.”