governments rule by fiat, by and large, and if they have a thing they feel they need or want to control, they can.
No. In the short run, maybe. But longer term, even the most dictatorial government needs some buy-in from the citizens; democratic ones need this more. And one sure way to get popular support is to encourage the populace to be panicked about stuff. H.L. Mencken probably said it best:
"The whole aim of practical politics is to keep the populace alarmed (and hence clamorous to be led to safety) by menacing it with an endless series of hobgoblins, all of them imaginary."
Our politicians are constantly encouraging people to be scared of something - maybe this year it's global warming but in earlier years the exact same role has been filled by: Iraq, Libya, muslims, "terrorists" of any variety, "glue-sniffing", "crack babies", "flag-burning", "GM crops", Alar, the "population explosion", "state militias", "killer bees", "christian fundamentalists", "cop-killer bullets", and many other topics. And yes, a few of these topics might even have been worthy of some concern, but you can't deny the overall dynamic has a consistent form: some faction of politicians (on the left or the right, it doesn't matter which) thinks that they can win elections by whipping voters into a frenzy about some scary new thing that will kill us all unless we put The Right People in charge. That faction seeks evidence to support claims of ruin and disaster; the opposing faction seeks evidence that the first faction's claims are specious.
Whichever factions are in power use the state's influence over science to encourage funding that is likely to produce results that make their side look better. results that make their side look worse will be ignored. There's also a Baptist/bootlegger component; some industries that benefits from the scare help pay for it. (in the case of the war on Iraq: defense contractors. In the case of global warming: various parts of the energy industry. For instance, oil companies that hope to profit by selling carbon credits, that have ties to "green energy", or that have especially good political connections such that they can hope to use new laws to get their own operations grandfathered in while hobbling their competitors.)
In short: Governments do generally benefit from scares such as catastrophic AGW whenever these scares can be used to justify giving more money, more votes, or more power to the political class. They benefit from raising alarm over global warming in exactly the same way they benefit from doing so in the War On Some Drugs and the War On Terror.
I honestly can't get into your head where it's easier for everyone disagreeing with you on every forum on the planet is part of a massive conspiracy being easier to accept than the possibility that atmospheric composition affects planetary cooling rates[emphasis added].
Right, there's your problem: What makes you think skeptics don't accept the possibility that atmospheric composition affects planetary cooling rates? The main disagreement at this point is over things like feedbacks - whether they are (and will continue to be) net-positive, how high they might be, how much harm that might cause over time interval X, how certain we can be about all this, what alternatives we have available to us, whether the cost of pursuing these alternatives outweighs their benefits (both now and in the foreseeable future), and basically whether we should be panicking yet or whether we can reasonably afford to wait and learn more.
You also don't need to posit a "monstrous conspiracy" where mere publication bias suffices: scary results are easier to publish and make for better press releases than non-scary ones. "It's worse than we thought!" makes a good headline; "It's not quite as bad as we thought" does not. :-)