Probably less than a hundred. We're not talking about a nuclear winter scenario. Look at the Chernobyl exclusion zone (most of which is not radioactive and is closed off as a precaution)
We’re talking climate warming by 2-3°C at least, no one knows how bad it’s going to be. I wish I would share your optimism. At the moment, scientists keep revising their prognostics for the worse each year.
Earth's ecosphere can adapt to tolerate that shift. It's better that we don't fuck it up, but earth has tolerated much hotter and colder periods just fine. It's us and the ecosystem we rely on that we're destroying.