I don't know. I believe the most likely outcome is effects that are serious, but significantly less serious than the mainstream consensus claims. I believe the error bars are much wider than anyone admits. I believe the narrow range of countermeasures that it's politically acceptable to move towards implementing are not particularly reasonable and will not be effective.

On what basis do you believe that?

Off-the-record conversations with (ex-) climate researchers I know personally. Which I don't expect anyone else to find convincing, but there's enough talk going around of researchers who got the "wrong" results getting pushed out that I found what they said more plausible than trusting the big-name journals etc.