recessiveMeme, thanks for an interesting question (and a great username).
The easiest way to answer your question is to ask another one: what would happen if through some amazing scientific proof, AGW were shown tomorrow to be completely false and untrue?
Well, the first thing would be that the IPCC would cease to exist … and so would the international travel, the nice hotels, the per diems, and all of the other perks that go with being a member of the IPCC.
Next, most climate scientists would be out of a job. If there’s no AGW, the importance of climate science goes from “more important than terrorism” to “a tempest in a teacup”. No one is going to pay somebody big bucks to study climate if AGW doesn’t exist.
Third, climate scientists would lose prestige and public visibility, authority, and power. Right now, when James Hansen sneezes, his nasal air speed gets added to the wind velocity of the latest hurricane and it makes headlines. If AGW didn’t exist, no one would care at all what he says.
So the answer to your question is power, employment, perks, prestige and public visibility.
Is there a conspiracy? I do not believe so. I believe that, like any organization, the IPCC is very unlikely to support any research that imperils its very existence.
And why is the picture one-sided? Well, how much time do you figure James Hansen spends looking for evidence to disprove AGW … and why should he? There’s no upside to it for him, and heaps of downside.
All the best,
w.
PS - my rule of thumb is “never ascribe to conspiracy what is adequately explained by common interest” …