Paris

United Nations secretary-general Ban Ki-moon addresses a meeting of local leaders at the Paris climate summit on 4 December. Credit: Christophe Morin/Bloomberg/Getty Images

Some describe it as groundswell of action to reduce carbon-dioxide emissions, others as a lush field of grass-roots initiatives. Cities, provinces, regions and businesses around the world have come together and promised to clean up the airborne pollutants that curl out of smokestacks and exhaust pipes — even as nations' efforts to forge a new climate treaty have stumbled over the last decade.

Nature special: 2015 Paris climate talks

Mayors meeting in Paris say that sheer numbers give cities the power to make a difference. Just over half of the world’s 7.2 billion people live in cities, and this proportion is projected to swell to almost two-thirds by mid-century. Local leaders, betting that huge investments will be made in extra construction for fast-growing cities, are forming compacts to build in a cleaner, low-carbon way.

An analysis published last week by researchers at Yale University in New Haven, Connecticut, found that the ambitious local commitments to reduce greenhouse-gas emissions add up to more than the global emissions of the iron and steel industries. Promises put forward by leaders of 228 cities alone would offset as much CO2 every year as is emitted by South Africa.

Bottom-up action

“Policies at the local level can make a huge difference,” said former New York mayor Michael Bloomberg, a United Nations special envoy for cities and climate change. “Local leaders are doers.”

The work of these doers was on full public display in Paris while negotiators representing 195 nations huddled together — often behind closed doors — to hammer out a plan to curb greenhouse-gas emissions. Celebrations, some bankrolled by Bloomberg’s charity, Bloomberg Philanthropies, put mayors and other city managers in the limelight for their work on the incremental, if mundane, steps needed to reduce the carbon emissions associated with modern life: implementing improved building insulation, energy efficiency and waste management.

Amid dramatic lighting and soaring music at La Gaîté Lyrique arts centre on 3 December, Clover Moore, lord mayor of Sydney, was recognized for working with businesses on low-emission apartment buildings, energy-saving lighting and air conditioning. “We’ve reduced emissions by 23%” from 2006 levels, Moore says, on the way to a 70% reduction by 2030. “It’s happening.’’

Stockholm received an award for a low-emission residential development that is part of the city’s plan to go fossil-fuel-free by 2040. Nanjing, China, won a prize for rolling out a fleet of electric buses and taxis; Washington DC got one for buying more wind power; and Johannesburg, South Africa, was recognized for issuing a green bond to finance a biogas energy plant and other projects.

Gregor Robertson, mayor of Vancouver, Canada, beamed as he accepted an award for a campaign to make his city the greenest on Earth. He lives in housing built as the part of the athletes’ village for the 2010 Winter Olympics; the complex warms its buildings through a heat exchange with its own sewerage system.

“It’s been a challenge to make progress without the national government,” says Robertson. Under former premier Stephen Harper, a champion of Alberta’s oil-sands development, Canada withdrew from the Kyoto Protocol climate treaty in 2011. But last month, Canadian voters ousted Harper, a Conservative, in favour of Justin Trudeau, a Liberal politician who champions climate-change action.

This bottom-up climate-action movement, organizers say, has grown from frustration over world leaders’ failure — at least so far — to craft a global game-plan to reduce greenhouse-gas emissions, despite agreeing on a ‘framework’ to do so at the 1992 Earth Summit in Rio de Janeiro, Brazil.

Pomp and circumstance

Under UN rules, no sub-national leaders, as they are called, have a seat at the negotiating table for the main climate agreement. So they held their own events — ones offering more glitz and glamour, with speaking roles for actors such as Robert Redford, Leonardo DiCaprio and Mélanie Laurent. "We reject the label sub-national,” said Washington State Governor Jay Inslee, pumping his fist in the air. “We think we are super-nationals. We are rockin’ on this issue."

At the climax of the day-long Climate Summit for Local Leaders at Paris City Hall on 4 December, participants rose to their feet, clapping and swaying to the song ‘Give Us Hope’, sung by the angelic voices of the Children’s Choir of Île-de-France.

Various groups have compiled lists of accomplishment and promises. At its 20th annual climate talks in Lima last year, the UN launched its own official tally, called NAZCA (the Non-State Actor Zone for Climate Action), after the series of mysterious ancient lines etched into the ground of the Peruvian desert. So far, more than 2,200 cities, 150 regions and 2,000 companies have registered carbon-reducing goals as part of this initiative.

How many of these goals are encompassed in national climate pledges on the negotiating table? The Netherlands Environmental Assessment Agency estimates the overlap at 70%. Thomas Hale, a political scientist at the University of Oxford, UK, who is tracking this movement, says that estimates vary widely. “We really don’t have the science yet.”

At one point this week, the litany of action plans gave way to an action hero: former California governor Arnold Schwarzenegger. After talking up his “million solar roofs” initiative, Schwarzenegger, a Republican, praised the achievements of his successor, Democratic governor Jerry Brown. Schwarzenegger called for an end to partisan politics, saying that onslaughts of wildfires, droughts and ferocious storms show that it is time to get real on climate change.

“This is not the movie world. We have no visual effects, no scriptwriters who help us write better endings,” he told city officials, who were using smartphones to snap his picture. “It’s our time to a march forward relentlessly like a terminator. We will not stop. We will not rest. We will not give up.”