Here’s a benchmark datum. Two million years ago the homo genus brain case was smallish. There ensued a continuous wave, at very roughly two hundred thousand year intervals, of severe weather pattern disruptions. Wet became dry, you name it – food gathering strategies, how to find shelter, dangerous species – everything turned *different*. Each time, adaptability to change improved survival. After ten or so of these, homo sapiens (v. sapiens) stood alongside homo sapiens (v. neanderthal) and homo sapiens (v. denisovan). Different varieties, not different species. For reasons we can only guess at, we voted the other guys off the island.
But global warming is a single weather change, likely a lot more severe than the continual changes that elevated sapiens (v. lucy) to sapiens (v. sapiens.)
Yes of course homo sapiens will figure this out – although at the same time the pressure to secure habitat and food could give rise to massive starvation, population movements, and war. Given that we have war-making abilities that can poison the planet and wipe people out in handfuls of millions with one bomb, what we call civilization is in serious danger. No of course sapiens will not disappear. After many dozens of centuries of successive small adaptations we may have “a new variety.”
But: bear in mind that a cloned, fully featured homo sapiens (v. neaderthal) would still be fully capable of interbreeding with homo sapiens (v. sapiens) and long-long-time-from-now homo sapiens (v. atomicus) would also be capable of interbreeding with v. sapiens, and doubtless also with v. neanderthal.
Species level changes absolutely take place, but the math says it happens only over spans of many thousands of generations. It’s been roughly one thousand since v. neanderthal, and close to two thousand since Australia lost contact with Asia. Evonne Goolagong, anyone? Fifty years ago she was a world tennis phenomenon, and of mixed aborigine/European parentage.
Oh, and Another Thing 