"But it's extremely important that the displays be very scientific and accurate. For example, it should not mix carbon with carbon dioxide, nor think carbon is a terrible element," says Shen.

The initiative shows the importance with which Hangzhou government treats environmental issues.

The scenic city at one stage was estimated to be annually discharging about 60 million tons of carbon dioxide, more than 7 tons per person.

It was not a good number for a city with a sizeable tourism industry.

Hangzhou in recent years has implemented various policies to improve the environment, such as public bicycles, economic structural adjustments, smoking controls and energy-saving boats on the Grand Canal of China.

Six low-carbons points have been identified by the government for the future city plan - low-carbon economy, construction, transportation, life, environment and society.

"A symbol of a low-carbon city is improving the social welfare and GDP growth while the carbon emissions doesn't increase," says Zhu Dajian, professor at the Economy and Management College of Shanghai Tongji University and an environment adviser to the World Expo 2010 Shanghai.

"An international criterion for a model low-carbon city is to make the per person emission under 10 tons annually when the per person GDP reaches US$20,000," he says.