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.

My personal point of view is that it seems fairly obvious that dumping tons of shit into the atmosphere is going to have an effect

This is a hollow argument. You characterise CO2 (and other waste gases?) as "tons of shit" which sounds suitably negative but doesn't actually mean anything. What are you using to classify some gases as "tons of shit" that then makes it obvious they'll have an effect? Not all waste products of chemical processes are dangerous; dumping nitrogen into the atmosphere will have no effect at all.