Climate Policy. China's peak carbon pledge raises pointed questions.

The 12 November announcement by China that it will stabilize its greenhouse emissions by 2030 has sent researchers scurrying to computer models of energy use and emissions, eager to understand the pledge9s implications—and the obstacles that stand in its way. The results suggest that if China achieves its goal, it could substantially lower the eventual peak of its annual emissions—now about 7 billion tons (7 gigatons)—compared with existing scenarios. In 2030, the peak would fall from as much as 18 Gt to as little as 14 Gt, suggests one forecast. Some studies suggest that emissions in 2030 could top out at just 8 or 10 Gt if China adopts even more aggressive policies, as it says it might. Critics of the pledge worry that China will rapidly increase emissions over the next decade—by building fleets of new coal-fired power plants, for instance—in order to make the 2030 peak as high as possible. But that scenario is unlikely, some experts say. Still, they predict China will face challenges in stabilizing emissions, including reaching a goal of generating 20% of the nation9s power from non–fossil fuel sources.