It is appropriate to concede – on the certainty point, at least – that the Fraser Institute’s anti-IPCC Report Summary is correct when it concludes, “…. there will remain an unavoidable element of uncertainty as to the extent that humans are contributing to future climate change, and indeed whether or not such change is a good or bad thing.”
The IPCC (Intergovernmental Panel on Climate Change) is extremely forthright in acknowledging uncertainty, going so far as to provide definitions (appended below) of its terms.
Thus we learn that it is only “very likely” that humans are causing potentially catastrophic climate change. We learn further that “very likely” means there is “> 90% probability.”
Which leads us to want to say two things. First, just to be sporting, we should say: Bravo! you Exxon-funded skeptics; you sure got us on that one.
But second, we’d like to say what we would say to any idiot holding a loaded gun with one empty chamber: It you’re looking for a game of Russian Roulette, we’re not interested.
Likelihood of the occurrence/ outcome
Virtually certain > 99% probability of occurrence
Extremely likely > 95% probability
Very likely > 90% probability
Likely > 66% probability
More likely than not > 50% probability
About as likely as not – 33 to 66% probability
Unlikely < 33% probability
Very unlikely < 10% probability
Extremely unlikely < 5% probability
Exceptionally unlikely < 1% probability