It depends on what you mean by "disaster" and "over specified." I will add that the IPCC, a body I accept as reputable, predicts a large range of possible outcomes with probability estimates, some of which I think can be fairly categorized as "disastrous." Global warming is a large potential human misery-causer, but not even close to an existential threat. For certain countries, such as the US, it probably won't be that bad, at least until the second half of this century.