Basically it is irreversible on a human level timescale. Many generations of life on this planet are going to have to adjust to higher average temperatures. It's going to be (and already is really) a mini-extinction event. Unless we don't change course, then it might be a mass extinction.
We can't even agree to stop causing damage. Agreeing to undertake a colossally expensive project to reverse the damage seems like a political impossibility. In 50 or a 100 years maybe, but not in the world as it is today.
