Copenhagen is often cited as a climate pioneer among European cities. It cut CO2 emissions by 187,600 tons annually in the late '90s by switching from coal to natural gas and biofuels at its energy plants. Its goal is to reduce emissions by 35 percent by 2010, compared to 1990 levels, even more ambitious than Denmark's national target of 21 percent cuts under the Kyoto accord.

In 1995, the city became one of the first European capitals to introduce a public bicycle service that lets people pick up and return bikes at dozens of stations citywide for a small fee. Similar initiatives have since taken root in Paris and several other European cities.

Next, Copenhagen plans to spend about $38 million on various initiatives to get more residents to use bicycles instead of cars.

Transport is one of the hardest areas for local leaders to control since traffic is not confined to a single city. Without stronger national policies promoting biofuels over gasoline, Vaxjo, for one, will never reach its long-term target of becoming free of fossil fuels.

But it's doing what it can locally. So-called "green cars" running on biofuels park for free anywhere in the city. About one-fifth of the city's own fleet runs on biogas produced at the local sewage treatment plant.

Using biofuels instead of gasoline in cars is generally considered to cut CO2 emissions, although some scientists say greenhouse gases released during the production of biofuel crops can offset those gains.

Vaxjo has also invested in energy efficiency, from the light bulbs used in street lights to a new residential area with Europe's tallest all-wood apartment buildings. Wood requires less energy to produce than steel or concrete, and also less transportation since Vaxjo is in the middle of forests.

Although Vaxjo is tiny by comparison, the C40 group, including major metropolitan centers such as New York, Mexico City and Tokyo, has been impressed by the city's progress and uses it as an example of "best practices" around the world.

"They're a small town," Reddy said. "Apply that to 7 million? It's doable but its going to take a lot longer."