Cities must play a critical role in shifting the world to a fossil fuel-free future. So why won't anybody help them?

Nothing defines modern life more than a sprawling city. More than half the world's population leads urban lives, and 1.3 million people abandon rural lifestyles every week for the promises of brighter lights, closer neighbors, and better jobs. Demographic forecasts indicate that two-thirds of world population growth during the next 35 years will be in cities.

If the world is going to lick global warming, cities across the world are going to have to work simultaneously—and urgently—to radically overhaul their electricity habits. Renewable energy needs political and policy support if it's to replace the gas and coal plants that are still being built to electrify cities. Residents need new infrastructure if they're going to plug in their electric vehicles. And buildings must be refurbished to reduce their hunger for power.

Fortunately, changes like these are underway. A report published by scientists volunteering for the United Nations concluded this week that "thousands" of cities are already "undertaking climate action plans." Unfortunately, the report, which was the 12th chapter in an assessment report published by the Intergovernmental Panel on Climate Change, also notes that cities can feel isolated when it comes to shrinking their carbon footprints.

"Cities are developing climate actions that are often not based on the best available science, don't take advantage of the systemic advantages of urban and land use planning, and are largely based on sector-level strategies."

Cities are left to develop their own climate action plans, and there have been few evaluations of their effectiveness, the chapter says. There's a dearth of scientifically-sound knowledge about which steps to prioritize. And there has been precious little research into how urban planners can make decisions that help the climate.

For those cities that do take action, there are few guidelines on how they can measure successes or failures, making comparisons difficult. San Francisco, for example, developed a novel method—then disingenuously claimed to have sharply curbed emissions after a power plant was shuttered and replaced with a transmission line that pipes in similar polluting power produced elsewhere.

"Cities are developing climate actions that are often not based on the best available science, don't take advantage of the systemic advantages of urban and land use planning, and are largely based on sector-level strategies," says Yale University professor Karen Seto, a lead author for the chapter, titled Human Settlements, Infrastructure and Spatial Planning. "In many cities, especially in developing countries, planning doesn't exist or is ineffective. In developed countries, there's a lot of inertia with existing land use plans, and a long history of uncoordinated efforts."

Laura Tam, a policy director at the San Francisco-based urban planning think tank SPUR who wasn't involved with the report, urged cities to persevere with their own initiatives while they wait for a climate treaty to be finalized next year that could force their hands.

"Many of the solutions are universal, such as renewable energy, mode shifts away from driving, energy efficiency, compact land use, and waste diversion," Tam says. "These solutions often have co-benefits exceeding their climate benefits, so they're worth doing for a whole host of other reasons."