We pollute. Pollution isn't good.
Global warming is happening. Look at the arctic ocean, among other issues.
Anthropomorphic Global Warming is claimed to be caused by CO2. CO2 is not a pollutant. whether AGW is real or not, when supporters do this kind of thing, it harms their argument (though I've seen plenty of blunders on the denier side too to be fair).
I think AGW and CAGW are interesting ideas and deserve to be studied and properly proven or disproven by appropriate scientists in the field. Unfortunately, the issue has been hijacked by those who would have us living in the stone age and have been running around chicken-littleing about global warming/global cooling/peak oil/nuclear/the steam engine/the wheel/fire since forever. As such, I stand in strong opposition to any change which could radically alter our quality of life until and unless we have much more solid proof. (This is the true implication of the precautionary principle by the way).