Science is just a process for knowing about the natural universe. It never gives us guidance on what we should do, it only tells us what is, and lets us predict what will be. What to do is always policy and politics. You can have a matter in which there is complete agreement on facts and theory, yet a disagreement on what we should do about it. While a solid scientific theory backed by good facts could tell us what is likely to happen if we take a certain action (or if we do not take an action) we then have to judge that result and how we value it. We have to look at the benefits and costs (everything has costs) and decide if we believe it is the best course of action, and on that point people may disagree.
That is, I think, a flaw many people make in talking about the AGW argument. They believe that since the facts (things like temperature and CO2 measurements) and the theory (the causal explanation of the relation of the facts) is solid in their estimation, that the course of action they believe should be taken is therefore scientific. That because there is a scientific theory at the core of what is happening, that means the conclusion they have reached is also scientific.
That's just not the case. Policy and politics aren't science. They can, and should, use science heavily to have good information as to the policy that is decided upon, but that policy is always a human construction, always a value judgement.
