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Gergis hockey stick withdrawn. This is what 95% certainty looks like in climate science.

In May it was all over the newspapers, in June it was shown to be badly flawed. By October, it quietly gets withdrawn.  The apology and press release are coming soon…right?

Thanks to help from the Australian Research Council it only took 300,000 dollars and three years to produce a paper that lasted all of three weeks. But it scored the scary headlines! It was “confirmation”, it was “unprecedented warming”, and it was a scientific certainty that was based on “27 natural climate records” and  “over the last 1000 years”. What could possibly go wrong? They had 2 whole proxies that went right back a thousand years, and they’d used computers (!) to rehash the data 3000 ways!  Frankly, I’m surprised it lasted three weeks. Let’s remember that if one single journalist had simply asked “how much colder was it in 1200AD?” Gergis, Karoly and the rest would have had to say “0.09 of a degree”. No one asked. But Gergis et al, had a proxy in Tasmania, and another in New Zealand, and they were “confident” they could calculate the whole grand continental collective temperature to nine one hundredths of a degree? Seriously.

As Mike E then pointed out in comments,  the error margin was larger than the result:

“The average reconstructed temperature anomaly in Australasia during A.D. 1238–1267, the warmest 30-year pre-instrumental period, is 0.09°C (±0.19°C) below 1961–1990 levels.”

Kudos to the team at Climate Audit (especially to Jean S and Nick Stokes) who uncovered a problem so significant, that ultimately it could not be ignored, even if it could be glossed over, delayed, and put on hold for months in the interim.

The science communication didn’t match the science

The headlines I listed back then:

“1000 years of climate data confirms Australia’s warming” said the press release from University of Melbourne. It was picked up by  The Guardian: “Australasia has hottest 60 years in a millennium, scientists find”; The Age and  The Australian led with “Warming since 1950 ‘unprecedented’. The story was on ABC 24  and ABC news where Gergis proclaimed: there are no other warm periods in the last 1000 years that match the warming experienced in Australasia since 1950.” It was all over the ABC including ABC Radio National, and they were “95% certain“!  On ABC AM, “the last five decades years in Australia have been the warmest.Plus there were pages in Science Alert,  Campus Daily  Eco newsThe Conversation, Real Climate* and Think Progress.

Perhaps commenters could get in touch with the news organisations and bloggers above and encourage them to correct the record? No doubt they will be racing to make sure Australians are not misinformed, or overly alarmed without reason.

Prof Lewandowsky tells us that even once bad science is corrected, people often remember the misinformation instead of the correction. So no doubt, he’ll be keen to help us repeat that the Gergis paper should not have been published, its results should not have been promoted, and their certainty was misplaced.

Now all scientists are human, and everyone makes mistakes, so it’s up to Joelle Gergis and David Karoly now to correct the record.

Will anyone thank the skeptical scientists who found the mistake?

(H/t Richard Tol, and Marc Morano).


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