PARIS — Cities including Seattle, Copenhagen, and Tokyo are taking the lead in slashing fossil-fuel emissions, picking up the baton from national governments that have squabbled for more than two decades over how to fight climate change.
Urban areas contain about half the world's population and will have two-thirds by 2050, says the United Nations. That makes them ''fundamental'' to tackling global warming, said Rachel Kyte, the World Bank's special envoy on climate.
The cities' steps range from electrifying buses to making cycle paths and requiring more efficient buildings.
Representatives of 195 countries are gathered in Paris to forge a global agreement to reduce emissions. A draft has been issued, and the next round of negotiations on the remaining details will begin Monday.
Prosaic as they seem, the efforts of individual communities are making a dent in global greenhouse gas pollution.
More than 600 towns, cities, and regional authorities that are home to 553 million have committed to reducing emissions by a total of 1 billion tons by 2020, according to ICLEI, a global network of cities and towns. That's almost as much as Japan produces each year.
''You see cities moving ahead, educating almost, the federal government about what's possible, what they need to do,'' Kyte said in Paris.
The work of cities is crucial because they produce 80 percent of economic output and 70 percent of greenhouse gas emissions, according to the C40 network of the top megacities. That means they're more efficient per dollar of output, but city dwellers emit more per person than rural inhabitants.
''Cities are centers of adaptation and innovation, and they don't have to wait for international negotiations or congressional action,'' said Shelley Poticha, director of urban solutions at the Natural Resources Defense Council in Washington. ''When cities get it right, which they increasingly are learning to do, they advance solutions that larger and even more complex entities like national governments can adopt.''
The cities with the most ambitious programs include Seattle, Oslo, Stockholm, and Copenhagen, all vowing to be carbon neutral. The Danish capital leads the pack with its pledge to do so by 2025 — 15 years before the Swedish capital and 25 before the other two cities. For comparison, the Danish government has promised a 40 percent reduction by 2020.
Copenhagen's measures include district heating, replacing street lights with LEDs, and making it easier for cyclists to get around, Morten Kabell, mayor of environmental affairs, said Tuesday in Paris.
London is slashing emissions by 60 percent between 1990 and 2025, compared with a national target to cut greenhouse gases in half. Shenzhen's goal is to lower emissions per dollar of economic output by 21 percent over five years ending this year. That outstrips China's goal for a 17 percent cut.
And Tokyo's goal of a 25 percent reduction over the two decades through 2020 compares favorably with Japan's target of a 3.8 percent reduction between 2005 and 2020.
Mayor Bill de Blasio of New York has pledged to cut pollution 80 percent by 2050 on top of a 19 percent reduction in the past decade. Portland and San Francisco seek 80 percent reductions by 2050. Austin, Texas, plans a 90 percent cut.