Once upon a time the future belonged to China—and China was going to be green. Greener than the hills of olde England.

"China is pulling ahead on the environment," was the title of a 2009 column in Forbes. "China is pushing ahead on renewable technologies with the fervor of a new space race," Peter Ford reported in the Christian Science Monitor the same year. "Green Giant" was the title of a 7,000-word thumb-sucker by Evan Osnos in the New Yorker, which spelled out the scale of the Chinese government's...