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Nature paper pushes wild exaggeration of 7-13C “climate sensitivity”! Even Gavin Schmidt calls them out.

Posted By Jo Nova On September 27, 2016 @ 10:19 pm In Global Warming | Comments Disabled

Lordy. Lordy. How did Snyder 2016 get past rigorous peer review and into a supposed “top” journal like Nature?

Carolyn Snyder did a 2 million year temperature reconstruction then assumed that all the warming in the whole record was caused by CO2, she then carried that correlation right through to reach the absurd conclusion that climate sensitivity is not 2 – 4C, but 7 to 13 freaking degrees. (Did she study climate science by watching Al Gore?)

Normally we’d expect a climate expert to know that orbital mechanics drive most of the changes.

Don’t look now, but Gavin Schmidt has done the right thing and pointed out a very silly conclusion that Nature and all their reviewers missed. (If only Nature had asked bloggers to review it …)

This obvious mistake has caught out a lot of the press. It was also missed by The ABC, The Conversation, Andrew Glikson etc etc.  The Daily Mail (UK) published a version by Associated Press, and they at least asked Michael Mann who said he “remains skeptical until more research confirms it” (as if!), and  Jeremy Shakun, who said it “seems too high”. Though AP buried those weak warnings and still went with the apocalyptic headline: Earth is warmer that it has been in 120,000 years – and is ‘locked in’ to hit its hottest mark in more than 2 million years, study claims. (Who forgot the Holocene? )

Andrew Glikson is an Earth and paleo-climate scientist at Australian National University, but he’s not expert enough to spot this gaping flaw. (Which is probably why he did so badly against a mere blogger in an epic five-round debate.).

As Gavin Schmidt says:

The paper claims that ESS is ~9ºC and that this implies that the long term committed warming from today’s CO2 levels is a further 3-7ºC. This is simply wrong.

The original study estimated a climate sensitivity of 7 – 13C:

Two million years of records show emissions could already warm world to dangerous levels

The Conversation. By Andrew Glikson, Australian National University

More sensitive than we thought

The new paper recalculates this sensitivity again — and unfortunately the results aren’t in our favour. The study suggests that stabilisation of today’s CO2 levels would still result in 3-7C warming, whereas doubling of CO2 will lead to 7-13C warming over millennia.

The research uses proxy measurements for temperature (such as oxygen isotopes and magnesium-calcium ratios from plankton) and for CO₂ levels, calculated for every 1,000 years back to 2 million years ago.

The ABC copied The Conversation but word spread pretty fast and only 4 hours later it added a new story with the very sedate title:

Climate change study accused of erring on rising temperature predictions

Prominent climate scientists have issued a warning that a paper published in the influential journal Nature sensationalised climate change predictions and used an “incorrect calculation”.

“The ratio that gave that, which was the very high sensitivity that she calculates, comes from a correlation between temperature and the carbon dioxide and other greenhouse gases from the ice cores, but as we all know, correlation does not equal causation.

“And in this case, the causation is the orbital wobbles of the Earth’s climate that are controlling both the temperature and the carbon dioxide at the same time and so that’s giving you an exaggerated view of how carbon dioxide affects temperature directly.”

Dear Dr Glikson — you asked to write part 6 in our debate –  you’re still welcome. :- )

h/t Colin, David B, Original Steve, Analitik

REFERENCE

Carolyn W. Snyder (2016) Evolution of global temperature over the past two million years, Nature, 00 MONTH 2016 | VOL 000 | NATURE | 1 LETTER doi:10.1038/nature19798
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