The wannabe Marxists are continually searching for reasons to attack capitalism. "Global warming" is merely the latest weapon.
Thats b/c Marxism thrives --no, scratch that-- Marxism requires crisis. Any kind will do: global warming, cooling, acid rain, ozone hole, overpopulation, energy dependence, water pollution, air pollution, snail darters, spotted owls...you name. It's all grist to their mill.
Case in point: Everyone reading this knows that the last thing leftists/liberals/environmentalists would ever want is for someone to come up with a safe, cheap, nonpolluting, endlessly renewable source of energy readily available to one and all.