Investing in lower-emission public transport, using more renewable energy, and increasing efficiency in commercial buildings and waste management in cities across the globe could generate $17 trillion in savings in current dollars by 2050, according to a recent report, Accelerating Low-Carbon Development in the World’s Cities, from the New Climate Economy, an advocacy group. At the same time, these low-carbon investments could also reduce greenhouse gas emissions by an amount exceeding the current annual emissions of the European Union or India.

The New Climate Economy is the leading project of the Global Commission on the Economy and Climate and examines how countries can achieve economic growth while dealing with the risks posed by climate change. Research for the commission was carried out by a partnership of leading economic and policy institutes, managed by the World Resources Institute.

“The steps that cities take to shrink their carbon footprints also reduce their energy costs, improve public health, and help them attract new residents and businesses,” said Michael Bloomberg, the U.N. Secretary-General’s special envoy for cities and climate change. “This report can help accelerate the progress cities are making in all of these areas.”

Nick Godfrey, the report’s author, notes how much cities are already doing to counter the effects of climate change. For example, 197 cities have bus rapid transit systems, operating like a rail line with their own corridors, special stations, and traffic signals. These carry over 32 million passengers a day. More than 850 cities have bike-sharing schemes and provide over a million bikes. And some cities are taking their commitment to bicycling even further; for example, Copenhagen is planning “super highways” for cycling.

Godfrey said the report—the first global analysis of projected savings from carbon reductions in cities—is intended to influence decisions at the climate summit in Paris in December. “We’re confident the recommendations are being looked at by a large range of senior decision makers,” he said, “and hopefully that will very much inform actions they take in Paris.”

The leading place of cities in today’s world led the report to note that “the infrastructure investments made in cities over the new few decades will lock the world into a higher- or lower-carbon path.” The report asks cities to commit by 2020 to low-carbon strategies that encourage “dense, transit-oriented, and livable urban forms,” says Godfrey.

Cities are also urged to join the year-old global Compact of Mayors and pledge to reduce greenhouse gas emissions, bolster resilience to climate change, and track their progress transparently. More than 130 cities have already joined.

The report emphasizes the importance of partnerships among cities and between cities and international players to work together to cut emissions and foster economic development.

The report calls on the international community—including development agencies, city networks, and organizations and development banks—to develop a package of at least US$1 billion to help accelerate and scale up low-carbon urban strategies. The money would be spent to do the following:

Help 500 or more of the world’s largest cities comply with the Compact of Mayors by providing technical assistance and resources of at least US$500 million.

Provide cities with technical assistance and capacity building for “bankable” programs and projects for low-carbon, climate-resilient infrastructure.

Enable cities to mobilize private finance for infrastructure investment. One way is to help cities improve their creditworthiness by enlarging the World Bank–led City Credit Worthiness Initiative to reach at least the largest 500 cities and the Cities Climate Finance Leadership Alliance.

Enable cities in developing countries to directly access climate finance—for example, in multilateral development banks and through dedicated windows in the Green Climate Fund and Global Environmental Facility.

Provide an enhanced platform for knowledge sharing and technology transfer among cities—for example, by supporting global city networks such as the C40 Cities Climate Leadership Group, Local Governments for Sustainability (ICLEI), and United Cities and Local Governments (UCLG).

Godfrey calls the $17 trillion in savings “a very conservative estimate, because it only looks at direct energy savings generated from investment, which are a small proportion of the wider social, economic, and environmental benefits of these investments.”

Investment in effective urban planning, he explains, can pay off socially and economically as well as in reduced emissions. Godfrey cites smart investment in public transport, which can lower travel costs, give the poorest access to jobs, and benefit the climate. Such investments, he says, are “a triple win.”

However, parts of the strategy used by the study could lead overall to economics losses. Wendell Cox, principal at Demographia and chair of housing affordability and municipal policy at Canada’s Frontier Centre, says that curbing development to create more compact urban forms produces its own problems. The resulting artificial shortage of land for building forces housing prices up, makes housing unaffordable for some, and leaves everyone with less money for other things, throwing some into poverty and causing income inequality to rise.

Cox also objects to the expectation of a major shift from automobiles to transit. As a practical matter, he says, a shift in demand to transit is very unlikely anywhere in the high-income world.

“Further,” he says, “no transit system has ever been seriously conceived that could replace the automobile or provide sufficient mobility throughout a major urban area.” He points out that even in as dense and compact a city as Hong Kong where most travel is on transit, the average one-way work trip takes 47 minutes—enough to interfere with the city’s economic performance.

“No transit system,” he says, “can get you from one point to another—except downtown—very quickly.”