June 2016 was the hottest month globally since records began in 1880, and marks the fourteenth record month in a row. For the great majority of people who’ve been following scientific findings on climate, there’s no great surprise there. There is very strong evidence both for the existence of a warming trend due mainly to emissions of carbon dioxide, and for the occurrence of a peak in the El Nino/Southern Oscillation index. Combine the two, and a record high temperature is very likely.
But suppose you were a strongly sceptical person, who required more evidence than others to accept a scientific hypothesis, such as that of of anthropogenic climate change. Presumably, you would treat the evidence of the last couple of years as supporting the hypothesis. Perhaps this supporting evidence would be sufficient that you would regard the hypothesis as confirmed beyond reasonable doubt, perhaps not, but either way, you would be more favorably inclined than before. And, if you were a public commentator, willing to state your views honestly, you would say so.
Does such a sceptic exist? I haven’t seen one, although I follow the debate fairly closely. In fact, in the 25 years or so in which I’ve been following the issue, I can only recall one instance of someone described as a “sceptic” changing their view in the light of the evidence. And of course, his fellow sceptics, who’d been promising that his research would reveal massive errors in the temperature record, immediately decided that he’d never really been one of them. In any case, while Muller was and remains a scientific sceptic, he’s no longer a climate sceptic.
Operationally, it’s clear that the term “climate sceptic” means someone whose criteria for convincing evidence are those set out by the Onion.
I’d be happy to be proved wrong (by counterexample), but as far as I can see, if the ordinary usage of the term “sceptic” is applied, the world population of genuine climate sceptics is zero.