As much as 72% of the world’s emissions in 2020 came from cities—and by the middle of the century, urban areas could triple in size. That’s why the latest climate report from the IPCC, the UN’s climate body, makes it clear that we need to build cities differently, as part of a long list of solutions that the world needs to quickly deploy to have a chance of avoiding the worst impacts of climate change.
“If you want to resolve the climate crisis, you need to resolve cities,” says Rogier van den Berg, acting global director for the Ross Center for Sustainable Cities at the nonprofit World Resources Institute. “It’s simple.”
Municipal leaders need to quickly enact a whole scale of changes, from retrofitting buildings to handling urban waste differently. But one critical piece is changing how people get around. If cities are redesigned to be more compact—the concept of the 15-minute city, where it’s easy to walk or bike to work and stores, and public transportation is also easily accessible—the report says that it could help cut urban emissions by around 25%.
Shifting to electric vehicles “is a huge opportunity,” Van den Berg says, but “you can’t cover it all with electric mobility. You also need to think about biking, walkability, proximity, and density of services.” When the urban design of a city changes, so do the people living there. Copenhagen wasn’t always dominated by bikes; now two-thirds of residents bike to work or school. After Paris started aggressively redesigning city streets, it now looks more like Copenhagen.
Making the shift in more car-centric cities in the U.S. is more challenging, though even cycling paradises like Amsterdam used to have a bigger car culture. New, fast-growing cities in Africa and Southeast Asia also need support to avoid sprawl and what the IPCC report calls “carbon lock-in”—designs that make it hard to cut emissions. More financing is needed at the right time so cities can grow in the right way, Van den Berg says. “Transport-related emissions in developing regions of the world have increased more rapidly than in Europe and in North America,” he says. “And that’s a trend that is likely to continue in coming decades. That means that we should not only look at what are the big emitters right now, but what are the emitters of the future.”
Cities can also do more to help capture carbon by adding more green spaces, the report says, from green roofs to urban forests. Already, city trees store around 7.4 billion tons of carbon, and sequester around 270 million tons of carbon each year. Adding nature back into cities also helps make cities more resilient in the face of extreme heat, floods, and other climate impacts.
Urban emissions are growing now, and by the middle of the century, if cities don’t make much effort, could grow to as much as 40 billion metric tons of CO2 emissions each year. But with ambitious action, that could drop down to 3 billion tons of emissions. The scale of cities is an advantage. “The growing concentration of people and activities is an opportunity to increase resource efficiency and to decarbonize at scale,” Van den Berg says. “It means that your big problem is your big opportunity.”