There are some of my fellow space nuts who think they've proven that it's at least possible for a massive scientific conspiracy to exist, and they point to research about Jupiter's moon Europa as their example. Astronomer Richard Greenberg, member the Galileo space probe team, alleges repression of the view of his team that Europa has a thin ice sheet and not a thick one that separates its oceans from the surface. He's got a book out that I've read, Unmasking Europa, that makes exactly this case.
At first read, it gives some support to an argument that parallels denialists, saying
It seems bizarre that political clout would be used to promote a scientifically weak position...[but] the situation is both familiar and disturbing....Deviation from [the scientific "party line"] is risky business....less secure [researchers] may feel pressure to toe the party line or move on to other fields.
Things go downhill from this point on though, if you're trying to use Europa as a metaphor for the alleged climate conspiracy. It starts with Greenberg's next paragraph:
The political aspects of the story of Europan science play out largely within the scientific community. In this way they are different from the even more ominous attempts at political control of science from the outside, such as the recent efforts to discredit the scientific consensus on climate change.
Yup, Greenberg might agree that there's a conspiracy related to climate science, except that it's about powerful interests trying to obscure the understanding that we are changing the climate.
On a broader level, Greenberg and other thin-ice supporters think science can work through the peer-review process, saying "even the hard-line isolated ocean are starting to hedge their bets" (page 34). He's doing exactly what the reality-based faction are suggesting to climate skeptics, that they prove their case in and through the scientific process.
Greenberg also argues that political power in Europa research was highly centralized in a small team that controlled access to Galileo imagery (current NASA missions allow easier and quicker access to data), and one government agency, NASA, indirectly controls their future careers. Climate change involves thousands of scientists in a broad range of fields - climatology, physics, oceanography, geology - where a small shadowy cabal can't run everything.
Another major distinction between Europa and climate is that Greenberg isn't arguing that his view has been completely excluded from the scientific process. He has even been included on the design team for the next mission to the Jupiter system that will definitively resolve the issue, although not until 2026.
So denialists will have to look elsewhere to show that it's even possible to find an example of a scientific conspiracy at the level they're describing.
Setting this all aside, Greenberg's book is well-written, persuasive, and has gorgeous photographs. He's also quite willing to name names about who's unfairly working against his viewpoint.
I have no idea who's right, and my opinion would be worthless anyway. Reading the wiki article on Europa is a good balance to Greenberg's point of view (the article acknowledges the lack of consensus, of course). I can say, however, that Greenberg's contrarian inclinations are obvious. For example, he claims it's good that the probe's main communication antenna failed, because this kept the researchers from being overwhelmed with data and could concentrate on a small set of images instead. That is simply ridiculous. Being a contrarian isn't ridiculous -they can sometimes make the big leaps - but it's something to keep in mind.
Greenberg and his book will either be considered a visionary or a footnote when the next probe finally gets to Europa. It'll be interesting to find out which.