You just confirm my point. The very fact that you use phrases like "policy implications of climate science", and "subject's ideological enemies" shows it's a highly politicized field. You wouldn't say "policy implications of quantum physics" or "chemistry's ideological enemies".
In case you didn't follow Climategate, it look that scientists from East Anglia University engaged in politics a lot, including dirty politics; and they were nothing like neutral scientists merely seeking the truth and letting others deal with policy. You may find their actions warranted due to some greater good, or not, but it's not normal scientific practice, and I'd be willing to bet against pretty high rates that you would not find anything like that on any evolutionary biology department.
That doesn't mean their findings are wrong. There are plenty of highly politicized issues where the mainstream is right or mostly right, but this rate is significantly lower than for non-politicized science. For example mainstream accounts of histories of most nations tend to be strongly whitewashed, as it's politically convenient. They are mostly accurate when it comes to events, but you can be fairly sure there are some systemic distortions. That's the reference class in which I put climate science - most likely right on main points, most likely with significant distortions, and with non-negligible chance of being entirely wrong.
On the other hand the moment climate scientists switch from talking about climate to talking about policy or impact of climate change of human well-being, I estimate that they're almost certainly wrong. There is no reference class I can think of which suggests otherwise, and the closest reference class of Doomsday predictors has just this kind of track record.
If you want some more, I did blog a bit about climate change recently: 1, 2, 3.
Look, when you are sure you are right everything confirms your belief.
Who are these 'neutral scientists'? When did climate scientists leave this class? What expert would just cede policy considerations to non-experts? I hope this class of people is a rare breed.
Climate science has obvious policy implications since CO2 is the problem.
Other sciences have had results that have clear policy implications. CFCs were bad. Marijuana is not that harmful. Cigarettes kill. Sometimes these results have helped develop good policy. Other times they were ignored.
Sayi...
I really liked Robin's point that mainstream scientists are usually right, while contrarians are usually wrong. We don't need to get into details of the dispute - and usually we cannot really make an informed judgment without spending too much time anyway - just figuring out who's "mainstream" lets us know who's right with high probability. It's type of thinking related to reference class forecasting - find a reference class of similar situations with known outcomes, and we get a pretty decent probability distribution over possible outcomes.
Unfortunately deciding what's the proper reference class is not straightforward, and can be a point of contention. If you put climate change scientists in the reference class of "mainstream science", it gives great credence to their findings. People who doubt them can be freely disbelieved, and any arguments can be dismissed by low success rate of contrarianism against mainstream science.
But, if you put climate change scientists in reference class of "highly politicized science", then the chance of them being completely wrong becomes orders of magnitude higher. We have plenty of examples where such science was completely wrong and persisted in being wrong in spite of overwhelming evidence, as with race and IQ, nuclear winter, and pretty much everything in macroeconomics. Chances of mainstream being right, and contrarians being right are not too dissimilar in such cases.
Or, if the reference class is "science-y Doomsday predictors", then they're almost certainly completely wrong. See Paul Ehrlich (overpopulation), and Matt Simmons (peak oil) for some examples, both treated extremely seriously by mainstream media at time. So far in spite of countless cases of science predicting doom and gloom, not a single one of them turned out to be true, usually not just barely enough to be discounted by anthropic principle, but spectacularly so. Cornucopians were virtually always right.
It's also possible to use multiple reference classes - to view impact on climate according to "highly politicized science" reference class, and impact on human well-being according to "science-y Doomsday predictors" reference class, what's more or less how I think about it.
I'm sure if you thought hard enough, you could come up with other plausible reference classes, each leading to any conclusion you desire. I don't see how one of these reference class reasonings is obviously more valid than others, nor do I see any clear criteria for choosing the right reference class. It seems as subjective as Bayesian priors, except we know in advance we won't have evidence necessary for our views to converge.
The problem doesn't arise only if you agree to reference classes in advance, as you can reasonably do with the original application of forecasting costs of public projects. Does it kill reference class forecasting as a general technique, or is there a way to save it?