It's the quietest story in environmentalism. In less than a year, China went from a polluting megapower to an up-and-coming clean-tech contender that promises to outpace America. Both countries responded to the recession by authorizing big stimulus plans with significant green components: 34% of China's stimulus money was green, compared with just 12% of funds in the U.S. That's good for the world — as the low-cost-manufacturing champion, China might be able to churn out enough solar panels and wind turbines at a price the rest of us will happily pay. And the green stimulus is a sign that China, after staying mostly silent on global warming for years, realizes that its old model of pollute then clean up simply isn't sustainable. For the U.S., however, China's gains may mean losses at home. A recent report by the Breakthrough Institute warned that the U.S. could be lapped by Asia in the clean-tech race.