I've always found it an oddly moot point whether humans caused climate change. If the climate changes past habitability, we won't be less dead because we didn't cause it, although I suppose it should let you know whether you could hope to change anything by changing human activity, but with various countries not agreeing and the problem of getting the entire race doing one thing, etc., I think we (or a decent subset of rich countries) would have to do some kind of large scale intervention besides trying to change human activity, like massive carbon capture.