It doesn't matter whether one believes it or not, a rational person will act according the least amount of likely possible negative outcomes. IE
If we do nothing and global arming is real, bad shit might happen.
If we do nothing and global warming is not real, nothing happens.
If we do something and global warming is real, and we fail to fix it (either through inaction or misguided action), bad shit might happen.
If we do something and global warming is real, and we fix it, bad shit won't happen.
Those are more or less the main possibilities.
Rationally, it makes sense to clean up / stop the shit we think might be causing warming.
So believe, don't believe, I don't give a fuck, just use your head.
The earth is over populated 3 times over, so its going at a faster rate.
Well that's just not true.