Give me a break. I answered your question. Perhaps I need to spell it out:
Money: Scientists and academes are largely funded by grants and donations. Their livlihood depends on these grants and donations. It doesn't do much good for the climatologist or whomever to go and say, "I've studied global warming at length, and I've determined it is a naturally occurring phenomenon and we have no more need to study it. Please stop sending grant money."
Rather, for the scientist or academe, it is a lot easier for them to say they have analyzed the problem, determined it's us, and that if you give them more money they are confident they can pin down the exact causes and identify solutions.
Power: From my previous point: the scientist/s and politician/s that claim they have determined the problem and have a solution are given more sway in their respective communities. They are regarded with reverence by their peers.
Self-Worth: Also tying in with the previous point, an individual achieves a better feeling of himself if he is able to identify a potential solution that is accepted by his peers.
But it's more than just that. As other posters were saying, there is somewhat of a herd-mentality. It is easiest, and gives a feeling of contentment, acceptance, and, consequently, self-worth, to go along with the pack than it is to constantly fight against the grain. If an individual's work is constantly being assailed by his peers, no matter whether the work is correct or he believes it is correct, it does damage to an individual's psyche.