It is already happening, but this is just the opening act. The show doesn't start in earnest for another 50-100 years at least.

That depends on how soon we get scared enough to act.

Or is it too late with anthropomorphic effects of deeds already done hitting their peak after decades?

It's late to act, but it's never too late to stop making things worse. The problem is the worst effects are far in the future and stopping the burning of fossil fuels is a gargantuan problem spanning all countries around the world. There are no palatable solutions - but doing nothing is even worse in the long term. People are generally awful in dealing with situations like that, and politicians even worse.