[dougweltman]

It would be helpful if we spoke about highly uncertain estimates like these differently, as the 2 degree rise is a middle-of-the-road "best guess" scenario in a complex system.

Their "best guess" isn't very good. What's your best guess for the number of COVID cases in your area in 2 months?

Things could be significantly worse than IPCC's estimate, or not that bad. We really don't know. From that uncertainty we should begin to think about things we can do to limit risk.

When there's relatively unbounded downside, you buy insurance (of various forms, financial, operational and other).