Under the premise "there is no real certainty either way", I'd choose to err on the side of safety (and enjoy healthier air, possible decreases in asthma and cancer rates, etc.). I think we have much to learn from the Native Americans who don't believe that land can be owned and see our resources as treasures.

The government was behind 9/11.

Videos on youtube prove it.

Personally, I believe in global warming. But I don't really see global warming as being the reason why we should take care of the environment - we should do that regardless of whether we believe in global warming and whether we like certain politicians or scientists or whoever or not. Global warming is just one issue - it's a FACT that we effect the environment, whether we're effecting it in that particular way or not. And it really isn't that hard to make some small changes and lead a "greener" lifestyle. A lot of those changes save you money too - what do you have to lose? It's a win/win proposition.