While it's undeniable that structural engineering has been around longer than climate science, scepticism should be based on performance, not simply the age of the field. The mainstream (IPCC) models have quite accurately forecasted global temperatures and sea levels over the past couple decades.

While climate science is a constant exercise in refinement (as all science should be), it's not a bunch of wild-ass guesses.

I don't know of anyone who claims there is anything specifically meaningful about 400 vs 410pmm, it is simply a new record.