The BBC is visiting eight areas of the world to find how people are preparing for climate change. BBC China analyst Shirong Chen and Beijing Correspondent Quentin Sommerville report from the Chinese city of Chongqing.
Chongqing is a Chinese mega-city that adds 1,300 new residents every day - or half a million new people ever year. And when they arrive here from the countryside, their carbon footprint almost instantly expands.
This grimy city is emblematic of the country's China's Copenhagen challenge; to continue to urbanise, modernise - and do so in a low carbon way.
The heat and carbon from China's factories have been making the planet warmer. But on the city's Nanshan mountain, there's a clue to China's strategy at UN climate summit.
There at the mountain's peak is one of the city's biggest cement plants, run by the French company Lafarge.
At Copenhagen, China is promising to curb its carbon emissions – reducing the carbon intensity of its economy by 40-45%, per unit of GDP by 2020.
The Nanshan cement plant is playing its part.
Originally built in 1973, the factory has been dramatically modernized, substantially reducing its carbon footprint.
Making cement requires a lot of energy. But at the plant, they're actually saving some.
They're capturing the extra gas and heat that comes off the huge cement kilns and turning it into power. The waste gases are captured then used to heat boilers, which produce steam to drive an electric turbine.
By doing so they’ve cut their electricity bills by quarter.
"This plant saves 40,000 tonnes of CO2 a year thanks to this device," says Kamil Beffa, the group president in Chongqing.
In the front of the plant a huge earth-mover, piles and distributes the factory’s mountain of coal. But this fuel has been augmented by something else - sewage slurry, which is being used to help power the huge cement furnaces.
These efforts are reducing the amount of coal used. Lafarge says it has cut the amount of carbon produced from each tonne of cement by 28% in the past three years.
Overall China has improved energy efficiency by 13% over the past three years, according to the country’s National Development and Reform Commission.
But this is a country addicted to coal, and that means even with its energy savings China's carbon emissions will keep rising for many years to come.
Technology could be the solution, at a test track outside downtown Chongqing, they think they're making progress.
The blue four-door passenger car is not much to look at. Its door rattles when closed, and the gearbox leaves a lot to be desired but this is China’s first home grown hybrid car.
The maker, Chang An auto, says it says about 20% of the energy of a regular car. China's government is pushing companies to take the lead, not just in electric vehicles, but in all green technologies.
"With support from the government, if we grow the market, and keep improving technology, then I think we won't be long before China overtakes the world in new energy cars," said Yong Ren, the Deputy Manager of the company’s new energy arm.
That is an ambitious goal.
Last month a million passenger traditional passenger cars were sold in China. So far this year, Chang An has sold only eighty of its hybrids.
Queues for lightbulbs
Even then, the offer of a government rebate, which reduces the price of the car by a third, hasn't been enough to attract more than a handful of buyers.
China's Copenhagen commitments come from the top. As well as improving carbon intensity, President Hu Jintao has promised to increase forest coverage by 40m hectares by 2020.
And there is a pledge to generate 15% of the country's energy from renewable sources by the same date.
But you do not get the sense that people in Chongqing, or in the rest of China, are suddenly considering their carbon footprint.
At a busy shopping street, energy-efficient light bulbs are being discounted, thanks to another government scheme. A queue, a hundred long, stretches along the road.
Construction worker Hua Ming Wu has bought a dozen of the half price bulbs.
"Every family needs many light bulbs, at least seven or eight," he says. "They're simply for saving energy."
But was he worried about climate change? "Probably... a little bit," was all he could manage.
Retired Miss Liu bought over sixty of the bulbs. "We just moved into a new house, we need lots of new bulbs. Everyone is responsible for the environment. Everyone should be worried," she said.
But most of today's customers are here because the bulbs are cheap, and it will cut their bills.
Even so, attitudes to climate change are changing in China, says Wu Chang Hua of the environmental organisation, The Climate Group.
"In many cases people link climate change with environmental issues," she says.
"We all know the environmental challenges here, the air is polluted, the water is polluted. We are struggling with it."
China is the world's largest emitter of greenhouse gases.
But per capita emissions remain low, and China - like India - says developed nations should fix the climate change problem they created.
For decades in China, GDP was all that mattered. Development at any cost.
But attitudes are changing - gradually.
Together with a series of environmental disasters, pollution has pushed climate change up the agenda. Although China does not want to be seen to be giving in to Western pressure, it is beginning to clean up its act.
Already a world leader in wind and solar energy, China aims to reduce its energy consumption, per unit of GDP, by about 20% from 2005 to 2010.
Chongqing, one of the largest cities in the world, epitomises the challenges facing China.
Its economy is based on manufacturing cars, motorbikes, iron, steel and aluminium. It is expanding so fast that 500,000 people are absorbed into the suburbs each year.
Can Chongquing, one of the planet's most polluted cities, go green?
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