The whole world is looking for ways to reduce greenhouse gas emissions and conserve energy. The most powerful strategy is to find solutions that handle both problems at once. For example, if new buildings are built with modern, energy-efficient technologies, they will drastically cut energy waste, and thus carbon dioxide, the principal greenhouse gas. At the same time, they will cut their demand for electricity, cooling, and heat, which will minimize the use of power plants and heating boilers.

I mention buildings because world-class building codes, properly enforced over time, can cut their energy consumption by up to 80 percent. We know this because California has now achieved it in new buildings compared to those constructed before the present code was introduced. New York City's mayor has calculated that three-fourths of his city's energy is consumed in buildings, so he is launching a new initiative to make them more efficient. China, too, can ensure its new buildings are efficient and built to last.

Energy efficiency has much more potential than most people realize. The pattern holds in industry, transportation, and other areas. Slash energy waste and you reduce greenhouse gas emissions and pollution.

What are the implications for China? It means that, in drafting the next five-year plan, there are terrific opportunities to win both the air quality and pollution battles, and help combat climate change. International experience suggests that carefully designed standards and pollution control strategies, if properly enforced, can make an enormous difference to air pollution and help with climate change.

China has some excellent experience on this front. China's energy efficiency standards for refrigerators, for example, will save around a billion tons of carbon pollution, even as they cut air pollution - sulfur oxides and nitrogen oxides - by millions of tons each. Fuel use in cars can be cut by 40 percent because of fuel efficiency standards.