After a period of selective leaking, very reminiscent of the way governments dribble out the bad news before a budget, the IPCC’s AR5 WGI Summary for Policymakers has seen the light of day. The big news is that where that august body was only 90% sure it was our fault that the earth was warming they our now 95% sure.
Quite what they are more certain of is however much less certain.
What is also not certain is where the 90% certainty came from in AR4 (buried in a footnote in the Summary for Policymakers is the fact that the reported 90% confidence interval was simply based on “expert judgment” i.e. conjecture) and as to the new 95% well …
The 95% is basically expert judgment, it is a negotiated figure among the authors. The increase from 90-95% means that they are more certain. How they can justify this is beyond me. Judith Curry. (Well worth a read).
None the less it is a propaganda device that works fairly well in moving attention to an immeasurable certainty from the more obvious certainty that observations are well out of step with the models that are supposed to predict our fate.
Observations that show no statistically significant warming for a decade and a half despite increasing carbon dioxide …
Or as AR5 puts it …
“Models do not generally reproduce the observed reduction in surface warming trend over the last 10 –15 years.”
Climate changes, has done forever, will do for ever. Carbon dioxide is one of the factors at work, we’ve known that since the 1890’s when Arrhenius developed the theory of greenhouse gases. What is still uncertain is what other factors are in play and the relative sensitivities of climate to them. And on climate sensitivity AR5 …
No best estimate for equilibrium climate sensitivity can now be given because of a lack of agreement on values across assessed lines of evidence and studies.
Fairfax and the ABC will no doubt concentrate on the increased certainty of impending doom. They made up their collective minds long ago.








