Many recent visitors to Beijing have been pleasantly surprised by blue skies rather than smog. In part, the cleaner air reflects heavy-handed policies: polluting factories have been moved away from the capital and other major cities, and coal-fired heating systems have sometimes been closed down before alternative gas facilities have been put in place. But the change in Beijing also reflects China's growing understanding that a truly green economy promises not only to improve quality of life, but also to create enormous opportunities for technological and political leadership.

In absolute terms, China is now the world's largest greenhouse gas emitter, accounting for more than 25 percent of the global total. Even in per capita terms, it has just overtaken the European Union average, while still at only half the level in the United States. This reflects an electricity system based 70 percent on coal, as well as China's global leadership in heavy industries such as steel, cement and chemicals. But China is already by far the biggest investor in wind and solar power, and is now canceling plans for further coal investment. And as China builds a low carbon economy, it enjoys a massive resource advantage.

A recent report by the International Energy Agency includes a color-coded map showing which areas of the world have the most wind and solar resources. The largest lies in China's sparsely populated western provinces of Tibet, Qinghai, Xinxiang and inner Mongolia. In principle, covering just 5 percent of that total land area in solar panels could supply China with 6,000 terawattt-hours of electricity per year, meeting its entire current electricity demand. (The wind potential is also massive.)