Other measures listed in the report will fall on city governments more than individual residents, like creating incentives for better building practices.
By using materials more efficiently, substituting green alternatives like sustainable timber or low-carbon cement, and ensuring that buildings are fully occupied, cities could reduce construction-related emissions 44% by 2050, according to the analysis.
These measures would also lower the cost of a new apartment by $10,000 in New York and by $15,000 in London, the report found.
"That makes construction and infrastructure a really exciting opportunity," Barrett said. "It ticks all the boxes."
Reducing car ownership would help shrink cities' emissions as well. Not only does burning gasoline produce carbon dioxide, just building a car racks up a big carbon footprint due to the impact of mining and manufacturing its components.
Convincing urbanites to abandon their cars will likely require government policies to promote alternative transportation. It's particularly important in a city like Los Angeles, Pincetl said, adding, "We can create a totally transit-viable region. But we have to be willing to combat the car."
The report also notes that flying is a major source of urban emissions, and one that won't get greener anytime soon. Air travel is growing far faster than progress on electric planes and low-carbon jet fuel, Bailey said.
So the authors recommend that city dwellers cut back on flights under 1,000 miles (think L.A. to Portland, Ore.) to one every two years, and to choose options like trains instead.
But these measures are not enough to bring urban emissions in line with global climate targets, the report found. Cities have to transition to renewable energy, make buildings more efficient and build low-carbon transportation options. Along with changes in consumption habits, such efforts would get C40 cities a third of the way to their emissions targets.
Beyond that, cities will need help from national governments on changes like moving power grids to clean energy sources. That would reduce the carbon footprint of the things city-dwellers consume, no matter where they're made.