The news on climate change has lately gone from being very bad to downright terrifying. Leading climate researchers are now issuing dire warnings, and their prognosis for the planet has become much worse over the last few years. Their models now predict that anticipated changes, like the shrinking of the polar ice sheets, are occurring at an accelerated rate, while feedback loops are magnifying the impact of man-made carbon emissions.

For example, rising temperatures will thaw out the Arctic tundra's permafrost, releasing carbon dioxide, in the form of methane gas, and lead to further warming. New findings indicate that more methane is stored in the permafrost than was believed, and it will accelerate the rise in global temperatures if released.

Given these reports, any positive development on climate change is cause to celebrate. China's recent pledge to reduce its carbon intensity by 45 percent by 2020 is one such development. Another is an Oct 6 paper issued by the UN International Energy Agency (IEA). The IEA has lowered its forecast significantly on global carbon emissions, not only because of the global economic downturn, but also on account of its belief that China will be emitting less greenhouse gases (GHGs) than was earlier assumed.

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China's pledge and these projected future trends make it much harder for climate skeptics in the US to use it as an excuse for doing nothing about global warming. Nor is it fair to claim, as do many of China's critics, that the carbon intensity reduction target is just a continuation of current trends. In fact, as William Chandler, of the Carnegie Endowment, has recently argued, meeting this goal will require China to significantly cut the growth in energy use relative to the growth of its economy. Economists call this ratio the "energy-GDP elasticity". If energy use doubles while the economy also doubles, then the elasticity is 1.

Chandler says that China's Copenhagen target requires a 4 percent annual reduction in carbon emission. If the Chinese economy keeps growing at an annual rate of 8 percent over this period, then the elasticity must be 0.5. This is significantly lower than 1-1.5 energy-GDP elasticity normally seen in developing countries. It is also below China's 2000-2005 energy-GDP elasticity, when energy use and emissions substantially exceeded economic growth.

Chandler further says that making this binding commitment poses political risks if China's economic growth slows. With a 6 percent annual growth rate, the energy-GDP elasticity comes down to 0.33. This more rigorous target is harder to reach in the absence of more rapid growth, as there is less investment in new, energy efficient capital equipment, requiring a greater write-off of the older capital stock, that is, factory closures. This, in turn, would lead to rising unemployment, threatening China's political stability.

Critics of this plan also fault it for allowing China's per capita carbon emissions to keep increasing. But this ignores the fact that much of this growth will occur from an extremely low base - lots of people here still lead difficult lives and consume very little energy. Indeed, Americans currently produce 4 times more carbon dioxide per person than do the Chinese.

And if China implements its Copenhagen commitment and the US reaches President Barack Obama's GHG reduction target, US per capita emissions would still be twice as high as that of China in 2020.

Thus China's commitment is far from trivial and makes it the first developing country to legally bind itself to serious long-term reductions in carbon emission. Can China reach these goals? And after 2020 will it be able to cap its GHG emission and reduce it by 30 percent or more by 2050?

Fortunately, grounds for cautious optimism exist here as well. The IEA's recent revised forecast on China's emissions reflects recent strong efforts by its government to reduce its energy intensity and step up the use of green energy sources. So with respect to green energy, China is clearly surging ahead of the US.

In 2007, for example, China required that large utilities generate at least 3 percent of their electricity from renewable sources. By contrast, in the US, this mandate is still being debated in the Senate.

This year China will overtake the US as the world's largest market for wind turbines - it has doubled its wind power capacity in each of the last four years - while State-owned power plants are competing to see who can build solar plants the fastest. Over the next decade, HSBC forecasts that China will invest more money in renewable energy and nuclear power than it will in coal- and oil-fired power plants. The construction of coal-fired power plants has now slowed to one a week and is still falling.

Moreover, while the US is dragging its feet in building long-distance energy transmission lines from rural areas with higher potential for wind energy to urban areas where the need for energy is greatest, China is moving rapidly ahead in this direction as well. The country is now developing ultra-high-voltage lines from wind and solar generation sites in the western region to cities in the east.

These measures underscore that the Chinese government understands very well the country's huge stake in combating global warming. Higher temperatures will lead to severe drought in northern and western China, regions already suffering from chronic and acute water shortage.

And rising sea levels threaten to inundate the country's wealthy coastal cities, including Shanghai.

To be sure, China certainly needs to do more in the future to combat climate change. But Obama should now focus on using his pulpit to emphasize the urgency of tackling climate change to the US public, large sections of which still believe in the junk science denying global warming. The US president also needs to the get cap-and-trade environmental bill, currently stalled in the Senate, passed. And if the US and China can exercise joint leadership in fighting climate change, we can be warily optimistic about saving the planet.

The author is an American corporate trainer and English teacher in Beijing.

(China Daily 12/17/2009 page9)