How would a layperson like myself judge what's in the IPCC report? The predictions are so dramatic that we have to act now and can't wait and see how it turns out. How is it different from this submission here?
First and foremost: read.
Second: don't demand certitude and table the idea that there's a universal judgement. Think: am I asking for an up/down vote on a conversation, or on an assertion?
Uncertainty can't always be driven down to 0. People usually expect this from other fields and yet understand when it is silly in their own field. (imagine: climate scientist forum noting cosmic rays, asking how any system can possibly be secure given memory safety causes security issues, and cosmic rays can flip memory bits, then hand-wringing about how they can even figure out what software research to trust)
This thread is itself a good example: OP has no issue with the research, or type of research, or anything, just is concerned how laypeople might believe it is certain and confirmed because it is in Nature. The paper itself makes no such claim, as the OP goes to great lengths to explain (c.f. it is statistical model)