Since we are already warming and we expect to be warming too much, the only argument against policy is strong new evidence that the warming is overestimated. Arguments for large uncertainty are definitely of scientific interest, but do not weigh against vigorous policy. Rather, quite the contrary.
Interestingly, there is a large overlap between those arguing for uncertainty and those arguing for laissez faire greenhouse gas policy. That position is fundamentally incoherent.
Lindzen and Spencer do not fall into this trap - they advocate for a low sensitivity with high confidence, a confidence that does not seem justified but at least is consistent with their policy positions. Broecker on the other hand argues for a very high uncertainty and very vigorous policy response. So climate scientists align coherently.
But people from outside the field often take the position that "this science is unsound, so how can we take action?" This nonsensical position is common among the people sidetracked by the millenial data sideshow.
The point is that there is a real sensitivity in the system that is clearly nonzero, and that there are various ways to establish a confidence spectrum as to what it might be.
That sensitivity propagates through various impact risks, each with its own confidence spectrum.
And whether we accept a dollar denomination or not, the aggregate risk is some combination of the component risks.
Much is made of whether the physics has a fat tail, but the fact remains that the impacts do have one-sided fat tails. If there are benefits to the coming changes, they are smallish compared to our worst fears (methane feedback, new deep ocean circulation, ice sheet collapse). This is why, the greater the emphasis on uncertainty, the greater the risk.
However often I say this, it seems to fall on deaf ears. Please make the effort to understand.
If the IPCC has understated uncertainties then it has understated risks.
I am amazed that those least concerned about uncertainty tend to be the ones talking about the risks the most while those most concerned about it tend to be the ones who are unconcerned.
This is clearly the result of professional denialist talking points playing up uncertainty. The thing is, they have managed to confuse just about everybody outside of science.
There is a great deal we don't know. The recent breakdown of the Arctic vortex with consequent severe winter weather in the eastern USA and western Europe is not something I had heard much emphasized in the predictions. The (amazingly immature) crowd of naysayers is now crowing about how little we know, and defenders of science are casting about for excuses. Wrong wrong wrong.
Things nobody saw coming are starting to happen. Already. This is bad news. Uncertainty is really very high. This means we had better get this carbon thing under control.
You keep using this word uncertainty. I do not think it means what you think it means.