The logic used and the predictions made are trivial. But the underlying facts and observations have been (politically, I presume) called into question. For instance in the recent CRU possibly-scandal, see Eric Raymond saying CRU published fake data and Willis Eschenbach describing how the CRU illegally denied FOIA requests for their weather data and even threatened to destroy them to prevent others from trying to replicate their studies.

Because this issue is so heavily politicized, I for one have no clear idea of the real extent of GW danger.