But the researchers argue that achieving the Paris Agreement goal of limiting planetary warming to 1.5 to 2 degrees — and avoiding catastrophic climate change — will require changing how urban areas “are designed, constructed, managed.”

The IPCC’s report called for cities to move away from urban planning trends that fragment cities into residential and business districts and rely on polluting habits like car commutes.

“Interventions that support a modal shift away from private motor vehicles and toward walking, cycling and low-emissions share, or public transportation … can deliver significant public health benefits and lower [greenhouse gas] emissions,” the authors wrote.

The assessment’s findings give backing to city leaders pursuing strategies like the 15-minute city concept, which seeks to redesign urban areas so that residents can work and have access to all the services they need within a 15-minute walk or bike ride. ParisBarcelona, and Rome are among the European cities that have embraced the idea.

The report also called on “established cities” like those within the EU to urgently take on the challenge of “replacing, repurposing or retrofitting building stock,” which the U.N. scientists argue is the easiest route to achieve the largest emissions savings.

Europe’s buildings are currently responsible for roughly 40 percent of the bloc’s energy consumption and 36 percent of its greenhouse gas emissions. Over 70 percent of the bloc’s population lives in urban areas.

“All cities can contribute towards a net zero future by integrating sectors, strategies and innovations,” said IPCC researcher Siir Kilkis. “Urban areas provide key opportunities for climate mitigation.”

The IPCC report stressed that making the required changes would require greater cooperation between different levels of government, as well as “substantial financing” that is beyond the budgets of city halls.

The statement echoes a frequent complaint from mayors who say they need greater, more direct access to European funds to implement EU legislation targeting emissions from buildings.

In a letter to Cohesion and Reforms Commissioner Elisa Ferreira on Monday, Heidelberg Mayor Eckart Würzner and other members of the Energy Cities network that support the energy transition described local administrations as “firemen lacking ladders and lances [with which to face] energy and social crises.” The letter appeals to the Commission to streamline financing processes and to make more local government projects eligible for EU funding schemes.

Separately, city leaders from the Covenant of Mayors wrote to Green Deal Chief Frans Timmermans last week calling for structural measures to “rethink the way our energy is consumed” and to “adapt our cities and living spaces” to the climate threat.

This article is part of POLITICO’s Global Policy Lab: Living Citiesa collaborative journalism project exploring the future of cities. Karl Mathiesen contributed reporting.

This article is produced with full editorial independence by POLITICO reporters and editors. Learn more about editorial content presented by outside advertisers.