The established superpower arose riding a wave of fossil-fueled prosperity. The emerging one, sitting on a wealth of coal, sees few reasons not to follow suit; after all, it has only just caught its wave (with India and others in hot pursuit).

Yet the tide can only be turned, a host of scientists and economists with varied perspectives agree, if China and other rising powers like India speed through the familiar path in nation building  resource extraction, industrial and economic growth, accompanying despoliation, and then environmental restoration and protection. If they don’t, their emissions will eventually swamp all other sources, according to many analyses.

Richard Richels, an economist at the Electric Power Research Institute, helped produce an ominous forecast: even if the established industrial powers turned off every power plant and car right now, unless there are changes in policy in poorer countries the concentration of carbon dioxide in the atmosphere could still reach 450 parts per million  a level deemed unacceptably dangerous by many scientists  by 2070. (If no one does anything, that threshold is reached in 2040.)

Libertarians say that once countries get rich, they’ll do the right thing for the climate. But critics of this view say the long life of carbon dioxide (and of sources like the coal-burning plants China is building at the rate of one a week) mean that waiting just compounds the problem beyond fixing.

Theories abound over how best to help China embrace emissions-reducing policies. One way, many scientists and scholars say, is to make nonpolluting energy sources cheaper than the unfettered burning of abundant fossil fuels. Right now they are far more expensive.