On Climate Sensitivity, Otto and Hansen - and Exaggeration from WUWT

Update below: In which Anthony Watts tells his readers "she'll be right, mate" and to take no notice of what the lead author himself says.


Today WUWT has picked up another article on climate sensitivity.  The authors, Otto et al, seem to have taken a not dissimilar approach to Lewis (2013), in that they based their workings on surface temperatures in recent decades including the temperatures of the most recent decade.  Unlike some other studies of climate sensitivity, the work does not appear to refer to evidence from past climatology, prior to the period covered by instrumental records.

The authors provide best estimates of Equilibrium Climate Sensitivity as 2.0 °C based on 2000-09:

The most likely value of equilibrium climate sensitivity based on the energy budget of the most recent decade is 2.0 °C, with a 5–95% confidence interval of 1.2–3.9 °C, compared with the 1970–2009 estimate of 1.9 °C (0.9–5.0 °C). Including the period from 2000 to 2009 into the 40-year 1970–2009 period delivers a finite upper boundary...Observations of the energy budget alone do not rule out an ECS value below 2 °C, but they do rule out an ECS below 1.2 °C with 95% confidence. The upper boundary is lowered slightly, but is also very sensitive to assumptions made in the evaluation process (see Supplementary Section S2). Uncertainties include observational errors and internal variability estimated from control simulations with general circulation models.

And of Transient Climate Response at 1.3 °C (0.9–2.0 °C) based on 2000-09.

This is lower than estimates derived from data of the 1990s (1.6 °C (0.9–3.1 °C); yellow, or for the 1970–2009 period as a whole (1.4 °C (0.7–2.5 °C).

Here is the write up by the Guardian, and from the BBC.  The opening paragraphs from the Guardian are:

Some of the most extreme predictions of global warming are unlikely to materialise, new scientific research has suggested, but the world is still likely to be in for a temperature rise of double that regarded as safe.

The researchers said warming was most likely to reach about 4C above pre-industrial levels if the past decade's readings were taken into account.

That would still lead to catastrophe across large swaths of the Earth, causing droughts, storms, floods and heatwaves, and drastic effects on agricultural productivity leading to secondary effects such as mass migration.

Let's moderate that with a dose of stark reality from Dr James Hansen, the "grandfather" of modern climatology.

The Exaggeration? (Yes, but maybe not so much as I first thought - see update)

Nic Lewis in his WUWT article says this new work is a : "new peer-reviewed climate sensitivity study published as a Letter in Nature Geoscience".  The article itself, however, is not published as a Letter.  It is published as "Correspondence", which is described as "Correspondence provides readers with a forum for comment on papers published in a previous issue of the journal or to discuss issues relevant to the geosciences."  There is no indication that the work has been peer-reviewed (see following Update). Describing the article as a Letter, when it is in fact Correspondence is still wrong and arguably an exaggeration, but not the double exaggeration I previously and erroneously thought it might have been.  Not really worth quibbling about after all - see following update:D

Update: This from Nature GeoScience: "Other types of Correspondence may be peer-reviewed at the editors' discretion". Nature has since advised me the article was peer-reviewed.

Don't get me wrong.  I'm not doubting the rigour of the analysis.  And I would welcome any news that climate sensitivity is lower rather than higher.  On the other hand I'm not about to accept estimates based largely on recent instrumental temperature records as the final word on the matter.  Particularly not when there are other studies of actual past climate change that suggest climate sensitivity may well be at the high end of the scale.  (Notice how Anthony Watts went all Dunning Kruger when he wrote about that paper).

Thing is, not one of us will be alive to see what is equilibrium climate sensitivity.  Some of us will, sadly, probably get to find out the transient climate sensitivity - at the time of doubling of CO2.  The medium and longer term effects we'll be leaving for future generations to grapple with.

Another Oddity

Another thing that's decidedly odd when you think about it.  Only a couple of days ago Anthony Watts was telling big fat lies about the 97% scientific consensus on global warming, trying to claim that more papers disagreed that humans are causing global warming than agree.  Now he seems to embrace a paper that assumes humans are causing global warming.  He also shows no lessening of his efforts to send us hurtling at warp speed (geologically speaking) towards a world that is too hot to handle.

I'll leave you with a comment from Anthony, whose frantic advocacy efforts to heat the world take him beyond rationality and morality.  Does he also lack any self-awareness?  Anthony Watts says:

May 19, 2013 at 3:08 pm  @Mosher I agree. Cook and Co. are advocates, so like Romm, they tend to do those sorts of things. Now, it appears Cook and Nuccitelli have reached the level of paid advocates.

Update: Watts tells his readers to take no notice of the authors

In a follow up article entitled: "Why the new Otto et al climate sensitivity paper is important – it’s a sea change for some IPCC authors" there is more ridiculous wishful thinking from Anthony Watts.  As if to prove the denier watcher's correct he writes:

With the modest rate of warming stated by Otto et al, the impacts of global warming are more likely to be positive than negative for humanity in the foreseeable future; increased crop yields for example.

Watts lauds the article, calling it a "sea change", but at the same time he dismisses out of hand what the lead author himself is quoted as saying with a sneering "Oh, sure":

Anthony snorts: The BBC says they had it all covered before and this new paper is “consistent” with previous works. Oh, sure.

Quoting the BBC:…when it comes to the longer term picture, the authors say their work is consistent with previous estimates. The IPCC said that climate sensitivity was in the range of 2.0-4.5C.

This latest research, including the decade of stalled temperature rises, produces a range of 0.9-5.0C.

“It is a bigger range of uncertainty,” said Dr Otto.

“But it still includes the old range. We would all like climate sensitivity to be lower but it isn’t.”

Let's add comments from Dr Sherwood, who is urging caution about assuming low climate sensitivity just based on the past decade:

Prof Steven Sherwood, from the University of New South Wales, says the conclusion about the oceans needs to be taken with a grain of salt for now.

"There is other research out there pointing out that this storage may be part of a natural cycle that will eventually reverse, either due to El Nino or the so-called Atlantic Multidecadal Oscillation, and therefore may not imply what the authors are suggesting," he said.

And finish with the final remarks from the lead author, Dr Otto - from the same BBC article - aimed squarely at deniers like Anthony Watts who wrote: "Meanwhile, in lower sensitivity land, “the pause” in global temperatures continues, and is approaching the Santer definition":

Is there any succour in these findings for climate sceptics who say the slowdown over the past 14 years means the global warming is not real?

"None. No comfort whatsoever," he said.