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Reader Comments (8)
It's funny how that 90/95% certain thing keeps coming up again and again. It seems to be the mantra of the movement and was used to particularly revealing effect, I thought, by Vicky Pope from the Met office in Roger Harabin's BBC piece.
What's odd is that the individuals keep repeating the 90% certainty quote, but as far as I can see – especially in the IPCC – it isn't anywhere. All material is hedged about by uncertainty caveats. Roger and all his associates have banged on about it for years, and are still doing it. They went out of their way in the piece (since they've been caught with their hands in the tail) to emphasise that the uncertainty was enormous. And then immediately contradicted themselves with the 90 percent mantra.
In fact Roger's whole piece was about stressing his discomfort with the fact he'd 'never been allowed to report it' Yeah, right)
So does anyone know where is this 90% certainty then?
Sorry, for 'tail' read 'till'.
Voice dictation. Barrrrgggh!
"Voice dictation"
I've often wondered if that worked...
Stuck
The SPM for WG1 of the FAR states:
"In this Summary for Policymakers, the following terms have been used to indicate the assessed likelihood, using expert judgement, of an outcome or a result: Virtually certain > 99% probability of occurrence, Extremely likely > 95%, Very likely > 90%, Likely > 66%, More likely than not > 50%, Unlikely < 33%, Very unlikely < 10%, Extremely unlikely < 5%"
All very subjective and not scientific.
The overall Synthesis report stetes
"Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations.[7] It is likely that there has been significant anthropogenic warming over the past 50 years averaged over each continent (except Antarctica)."
Hence, since it is very likely, then the likelihood is >90%, according to expert judgement!
Easy peasy.
Shame that there's no evidence to back up that 'very likely' tag.
James: Voice dictation works approx 'very likely'.
Between you and me, the MetOffice method was an embarrassing disaster. We've decided to make our uncertainty estimates more impartial and scientific in future. We've hired a specialist consultant from William Hill.
As Philip Bratby has pointed out above, the IPCC's levels of certainy are all based on "Expert Opinion" - not on some result spewed out by the climate models using some horribly clever algorithm. Oh no - the IPCC simply asked the "experts" for their opinions!
The percentages, then, are meaningless from a scientific point of view. All they show is the level of belief amongst the "experts", and nothing else.
NEWS FLASH - God's Existence Finally Proved! Today, experts at the Vatican SHOCKED the World and Professor Stephen Hawking by announcing that they are "virtually certain" that God exists, with > 99% likelihood ...
Roger Harrabin suggested some amendments to the words in the cartoon so we don't
think Bob is actually being uncertain about climate science, more that he is
uncertain about communicating uncertainty, in a certain uncertain way.
Certainly, say I...so here is the update
http://www.cartoonsbyjosh.com/harrabin_scr.jpg