Becoming a low-carbon city has become the latest trend as China steps up efforts to reduce its energy consumption and cut greenhouse gas emissions.

At least 100 Chinese cities have announced plans to become low-carbon cities. Lhasa's plan to build a "sun city" powered by solar electricity is the latest example of the drive. But their ambitious ideas are still on the table without any specified targets.

"China has no real low-carbon city yet," said Jiang Kequn, a researcher at the Energy Research Institute of the National Development and Reform Commission and an advocate for a low-carbon economy.

While cities across China are bracing themselves for a transformation to a low-carbon society, many of them have taken different approaches. In Baoding, Hebei Province, a mansion covered with solar panels has become the city's new landmark tower. In Dezhou, Shandong Province, solar-powered street lamps line the city's roads and alleys.

Jiang points out that while initiatives to build low-carbon cities should be encouraged, they are difficult to fulfill. The most popular way of building a low-carbon city involves cutting greenhouse gas emissions of buildings, transportation and industries to drive down the overall emissions of the city.

London became the first city to gain worldwide attention for its low-carbon plan, announced in 2007 by former mayor Ken Livingston. The city planned to cut carbon dioxide emissions by 60 percent by 2050.

In China, cities do not measure carbon dioxide emissions, and few have standards or monitors in place. Some industrial parks are built under a banner of using low-carbon energy, but they have been found to manufacture low-value products that consume many resources while causing pollution.

Still, officials think the interest in building a low-carbon society is better than nothing, even if little has come of it.

"Even if enthusiasm for a low-carbon city is window dressing, it is better than nothing," said Zhuang Guiyang, an official of the Chinese Academy of Sciences. "At least it represents people's growing awareness of low-carbon."

Zhuang said a clear change in attitudes happened last year after the Copenhagen talks, where China promised to cut carbon dioxide emissions by 40 to 50 percent by 2020. A few years ago, Zhuang said, it was difficult to get local governments to cooperate on low-carbon projects, but since the Copenhagen conference, government officials now show great interest in them.