Well, part of the problem is that so much of what's going on is unprecedented, unknown and undetectable. We're trying to plot an estimate for an entire planets climate system and it's hard enough to get even local predictions correct.

But what we can rationalize about is that our current effects on the climate are already having dire effects, worsening disasters and increasing extremes. The bug windshield phenomenon is one example of a potential downstream shift.

By the time we have a more concrete timeline the odds are that it'll already be here and far too late.