Compact pedestrian neighborhoods, urban forests and even carbon-sucking technologies must make the to-do list of more city mayors if the world is to avoid catastrophic climate change, scientists said at U.N. talks on Monday.
Governments at the climate negotiations in Poland are at loggerheads over how to respond to a U.N. scientific report that says temperatures could rise 1.5 degrees Celsius (2.7 degrees Fahrenheit) from pre-industrial times as early as 2030.
But city representatives said they had moved beyond that battle, and were now taking action.
Two networks representing thousands of cities said in a statement that the scientific findings were "unequivocal," and cities were "key to developing a 1.5C future," a tough challenge requiring rapid, large-scale shifts.
In the 2015 Paris Agreement, governments agreed to keep global warming to "well below" 2 degrees Celsius, and to strive for a 1.5 degree limit.
A new guide penned by 18 authors of the 1.5C report, issued in October by the Intergovernmental Panel on Climate Change (IPCC), translates its country-focused findings into specific information that can be used by city planners.
The authors, spanning the globe from the United States to India, said they had produced the accessible guide for cities "because without them, there will be no limiting global warming to 1.5C."
People living in urban areas are expected to comprise two-thirds of the world population by 2050, and will generate a growing share of heat-trapping emissions, the report said.
They are already responsible for an estimated 75 percent of emissions, according to UN Environment.
IPCC author Seth Schultz said the team had produced the guide voluntarily "because of the importance and significance of cities in ensuring a climate-safe future."
The document was backed by C40, a group of cities tackling climate change, and the Global Covenant of Mayors for Climate and Energy, an alliance of cities and local governments.
"Urban policymakers must seize the opportunity," said the guide. "The tools are at hand."
Climate-related risks such as falling yields, health problems and slower economic growth are projected to be far worse if warming tops 1.5C, the IPCC report said.
The cities guide said limiting global warming to 1.5C would turn, in part, on the feasibility of urban actions and policies.
Buildings along city streets will need in 2050 to produce about 90 percent fewer emissions than in 2010 to meet the goal.
Cities could also become sites for deploying emerging technologies that suck carbon out of the atmosphere to limit warming, the guide noted.
"Cities are ready to lead," Paris mayor Anne Hidalgo, who chairs the C40 network, said in a statement.
The IPCC plans to issue a special report on climate change and cities during its next multi-year assessment of climate science that will begin in 2022 or 2023, said Schultz.