[Certhas]

FUD. The statement that we need drastic changes is not dependent on the details of the projection and is not based on it. Further, climate models have correctly predicted the heating we have already caused.

We have known the rough level of the climate sensitivity (delta T per doubling CO2) in the current macro state for decades. We have observed it. This science is incredibly settled. We don't know where the tipping elements are and we don't know how the impacts will be distributed.

Questioning the credibility of people calling for action might look like you are being the circumspect and rational one, asking for action proportionate to the evidence. In reality you are endorsing an ignorant position that ignores the evidence we have. If this is not wilful ignorance then please read up on this. The IPCC report summary is a good spot to start. Sceptical Science also often provides good writeups: https://skepticalscience.com/climate-sensitivity.htm

The fundamental physics that drive the sensitivity are straightforward. Energy balance and water vapour. That gets you a ballpark figure that is confirmed by the last 100 years of emissions.