During weekends, bicycles whizz by and families stroll down streets that are often clogged with honking cars. The city's new justice building is rising from an eco-friendly district of northern Paris: a fabrication of stone and glass that will feature a massive rooftop garden.

The French capital itself is transforming as it aims to be the linchpin for an ambitious global plan to tackle climate change.

"The city of Paris is changing - so are other big cities in the world," said Paris Deputy Mayor Patrick Klugman. "We can have snowstorms. We can have floods. We can have things we are not used to. So we are getting prepared to face them," he told DW.

Under the plan, the French capital will create a web of new cycling lanes, walking trails and green spaces. It aims to build hundreds of solar panels, create low-energy social housing and support green industries. The overall goal: cutting greenhouse gas emissions by 75 percent by 2050 from 2004 levels.

Plans by architect Vincent Callebaut of what Paris could look like shows a bizarre, futuristic city, with plans sprouting from every building.

Cities taking initiative

Recent findings on climate change are lending a new sense of urgency. Experts say 2015 is likely to be the world's hottest year on record. Fires and droughts in the United States, a sweltering summer in many parts of Europe and globally perhaps the strongest El Nino ever are all signs pointing toward climate change.

Meanwhile, many worry about the slow pace of climate talks. "There is a risk of failure," French President Francois Hollande warned during a press conference at the beginning of September, amid a wider European refugee crisis. Without a successful agreement, Hollande said, "We won't see hundreds of thousands of refugees over the next 20 or 30 years - we'll see millions.”

But as climate negotiators bicker, municipalities are moving ahead. Paris is among many megacities cutting their greenhouse emissions. With experts estimating that three-quarters of humanity will live in urban areas in 35 years, the race is on to green them.

"So far, cities are the problem spots," Klugman said. Greenhouse gas emissions, other kinds of pollution and other environmental problems are concentrated in urban areas. "Now, there's a common will to make cities the safe places to be for the environment," he added.

Paris practicalities

And some of changes are already underway. A new tramway ringing Paris is nearly finished, and the metro is being extended. Chunks of the capital are closed to cars on weekends, and there are plans to close some traffic arteries altogether.

And after launching its iconic bike and car sharing schemes, the city will soon add electric motorbikes. On September 27, the city went car-free in a bid to fight congestion and pollution.

"When I first got to Paris, the city was created for cars," said New Yorker Richard Boris, who has been living in Paris on and off since 1968. "That certainly has ended," Boris told DW. "Paris has always been a walking city - and the fewer cars to impede that, the better off we are."

Parisian Lamine Camara, unlocking one of the city's nearly 13,000 bicycles from its stand, has gone green for practical reasons. "The Velib [bike-sharing scheme] is a good idea for getting around quickly and easily," he said. "I'm not really an environmentalist, but if I can help out, why not?"

While polls show most Parisians support the city's climate change plan, commuters are underwhelmed by some measures - such as a ban on diesel fuel by 2020. A group called 40 Million Motorists has launched an online petition against the city's plans to permanently close a major artery by the Seine River.

Driver Fernando Figuera, describing the challenges of daily traffic in his work to deliver cabinets from the Yvelines region outside Paris, said: "Fighting climate change is a good idea, but there must be compromises."

Paris can do more

Yet many environmentalists believe Paris can go further. Vancouver, Portland, Copenhagen, and Freiburg are among the cities often ranked the world's greenest. Paris is quite a bit further down the list.

"The roadmap is quite good, the ambitions are quite good - but the action is taking time," said Charlotte Izard, an expert at the Climate Action Network, a non-governmental organization housed in an eco-friendly building just outside city limits.

"They can do more with bicycles, public transportation, increasing nature in the city," Izard added of municipal authorites. "We don't have time to wait."

But Klugman pointed out that doing more is a shared responsibility. "It's a common battle, that we cannot win it without having the population, the companies, everyone involved."

And the first challenge for the city, he added, would be having "everyone on board to face climate action."