On the other hand, once it is observed it will be too late to reverse.

We have on a small scale. Methane is escaping as the permafrost thaws. Boreal forests are also burning down as their climate warms. Reduction in polar ice changes the albedo of the earth to reflect less heat.

At a certain point sufficient warming could trigger a cascade. So far we haven't done that, but it's incorrect to say there's been no release of stored CO2.

Earthworms are moving north and accelerate the breakdown of organic matter in arctic regions too.