As you may have heard by now, in 2007, China is set to surpass the US in the emission of greenhouse gases. This has many implications for the concept of environmentalism, and for the geopolitical landscape.
China takes 4.3 times as much energy as the US to produce each dollar of GDP. Thus, China, with an economy less than a fourth the size of the US, already emits more. It is true that China's per capita emissions are much lower than the US due to China's much greater population. However, the US is not the highest in per capita emissions either. Small nations like Canada and Norway top that list.
Now consider the implications of this for the near future. By 2012, China's emissions will be a clear 20% higher than the US, which is a delta too large to ignore. The environmental movement has some people (like Thomas Friedman) who genuinely care about reducing pollution. However, a large subset are merely anti-US, anti-capitalism radicals who seek to mask their agenda within the altruism of environmental concerns. A beloved non-Western, undemocratic nation being a bigger polluter than the US is simply too inconvenient of a reality for their agenda. This will split the environmental group into two opposing factions - those who truly seek to curb emissions worldwide, and those who are merely driven by anti-Americanism and anti-capitalism. This civil war will be interesting, to say the least, and the purging of the phonies could just be the best thing to happen to the environmental movement, making it palatable enough for greater participation from mainstream people.
Furthermore, this is an example of point 10) in my essay on Why the US Will Still be the Only Superpower in 2030. China is not prepared for the burdens of being the primary recipient for blame on a major global issue. As the heat on the US reduces at China's expense, China will find that the upper rungs on the ladder to superpowerdom bring the attachment of heavy weights that make each subsequent rung increasingly difficult to scale. Getting to the top is just not as easy as it may seem, as China will continue to discover.