This is not the right way to look at the issue. If the low-level data itself can not be made any more convincing, the only real option is to ignore staunch deniers. The right way to look at this, given the way it has been politicized, is to look from the perspective of any proposed policy change. And then for each given change, be sure that the evidence and arguments are solid at all levels of the discussion. That is:

1. The observed climate data is valid and complete.

2. The predictive models are reliable and sufficiently comprehensive and objective.

3. Specific problems are clearly articulated.

4. Proposed policies will solve the clearly articulated problems.

5. The proposed solution is realistic to implement worldwide, wont' have any unexpected side-effects, and won't cause worse problems than the problems it's solving. Negative side-effects should be acknowledged and addressed as best as possible.

While I have seen arguments that at least touch on most of those points, it's very difficult to arrive at level 5 and not have ANY room for mistakes or legitimate differences of opinion and perspective. So while it's nice to bitch and moan about the wild conspiracy theorists challenging the facts established at the lowest level, the opposition is just as justified bitching and moaning about all the political actors who have already decided what solution they want, and are just doing whatever they can to make sure that solution becomes policy, no matter the consequences.