Any and all climate shifts will be horrific for certain areas and wonderful for others. Like actual extinction for a lot of animals/plants in one spot and then others completely overrun with the exploding populations. That's just how fragile a lot of evolutionary lines are.

But that's also the natural course, as history is littered with it happening completely on its own over and over for millions of years before humans even arrived. Whatever effects humans can have on it will be within the Earth's own personal cycle.