Every once in a while, someone brings to my attention a new article or video attacking the mainstream position on anthropogenic climate change, and I pretty much always end up responding with one of the following responses:
1) "This doesn't say anything that would be particularly troubling to the mainstream position. It simply highlights one area of uncertainty -- one which has already been acknowledged by the mainstream community. The balance of available evidence still supports the position that humans are likely having a significant impact on the climate system which will probably continue into the future, but considerable uncertainty does indeed remain. As scientists learn more, they could discover that they overestimated the significance of certain phenomena, or that they posited causal connections which either aren't there or are canceled out by other factors. But they could also find out that they underestimated those things, or that things are likely to be a lot worse than they thought. We simply don't know. The mainstream estimates provide "best guesses" about what might happen in the future, but there are no guarantees. Issues like this one show us just how much more we have to learn. However, it would be irresponsible to dismiss the mainstream position because it is grounded on science that is wrought with some uncertainty. As I said above, the balance of evidence points to some reason for concern, and that needs to be taken very seriously."
I think the paradigm cases which warrant this kind of response are the objections to proscription and tuning in models, questions about model resolution and intracellular processes, and uncertainty surrounding the impacts of aerosols, oceanic heat-transfer processes, changes in cloud dynamics, and solar phenomena (including the issue of cosmic rays). I like giving that kind of response a lot because I think it puts into perspective both the fact that we have a lot left to learn before we can be comfortable with our understanding of the climate system, and the fact that we can't just expect the scientific community to hold off on making predictions until we have perfect knowledge of what's going on.
The other kind of response I sometimes give goes something like this:
2) "Why would you listen to this person? He/She is not a climate scientist, clearly has not read the part of the IPCC report (or any other significant mainstream publication) that addresses the issue he/she is discussing, and seems to think that issues in climate science can be discussed through one-liners. If you don't want to actually learn about the issue at hand, then don't go around spouting your ignorant opinion, or tossing links around leading to other people spouting their ignorant opinions. It's infuriating that people even pay attention to this nonsense."
Unfortunately, I seem to give out more (2)'s than (1)'s by a wide margin. What needs to be recognized by those who receive these answers is this: The points discussed here do not apply with any more effectiveness to climate change alarmists or climate change denialists. Members of both parties are very often guilty of not knowing the first thing about the subjects that they're talking about (especially the individuals who come to deserve the (2) answer). People need to acknowledge that while the mainstream scientific position is not necessarily perfect, it is at least not flawed for simple, obvious reasons, or because there's some perfectly legitimate and groundbreaking scholarship out there that simply was never heard of by anyone.
There are certainly some large uncertainties, and a lot still needs to be done in order to get a proper handle on what we can expect for the future. But rather than try to frantically poke holes in the mainstream position, people should be spending their energy learning more about the basic concepts on which that position is built. Otherwise, I'm going to keep having to hand out more of those (2)'s, and I don't want to do that.