Monday, May 20, 2013

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

Sou | 6:03 PM Go to the first of 12 comments. Add a comment
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.


  1. The new paper has an impressive list of authors and I think it deserves to be taken seriously.

    Does anybody really believe that Watts and his disciples would accept a climate sensitivity of 2 degrees?

    1. Yep. But highly conditionally: they'll accept it for the five minutes needed to use it as a stick to beat somebody,anybody with...then they'll forget it,'cos after five minutes Anthony will throw another stick for them to fetch.

    2. I don't disagree about taking it seriously, Lars. But only in the context of all the other recent papers on climate sensitivity using a variety of different approaches, for example.

      I am particularly concerned about what we learn from past climates. IMO that's much more relevant than the surface temperature record since since 1970, let alone since 2000.

      I also don't like it when people place too much emphasis on the transient response. (I'm not suggesting Otto et al do this, but the likes of WUWT most certainly do - when they acknowledge global warming is indeed real.) I like to think we will consider the needs of humanity over coming millenia, not just 50 years hence.

    3. Indeed, this is the "Quote of the Week" at WUWT:

      “The influence of mankind on climate is trivially true and numerically insignificant.” Richard Lindzen [H/t Tom Sheehan]

  2. Observe how Nic Lewis' value -- based on recent data, which is prone to change, and vaunted at places like Bishop Hilll weeks earlier -- is lower even than this new research, conforming what James Annan wrote soon after, that although Nic's math is sound "some of his choices are dubious and will have acted to underestimate the true sensitivity". Another decade of data can alter the equation considerably, but let's hope things stay constant and politicians use the extra time to enact hard measures. Of course Watts & Co. will (ab)use the results to prevent the kind of action the co-authors stress is still necessary to avoid serious disruption. No surprise there.

  3. Comments by some of the authors (in NewScientist):

    "If previous estimates [of how the climate will warm] were true, keeping the world below 2 °C would have been almost impossible however big our emission cuts," says Piers Forster of the University of Leeds in the UK, who contributed to the new study. "Now it looks like we have a chance, so we should take it."
    "Prior to this, a lot of us were feeling quite gloomy that whatever we did, we'll go over 2 °C," says Forster's colleague Myles Allen of the University of Oxford, UK. "It's not a foregone conclusion any more." That means the UN climate negotiations could still succeed. If a deal comes into force in 2020, and leads to rapid emissions cuts, "there remains a good chance we could hit the 2 °C target", says Allen.

    You won't find Watts quoting that.

    1. I believe we need a new deal well in place before 2020, though it's probably not going to happen.

      Thing is, many renewables are now on par if not cheaper than fossil fuels. The private sector is, as is often the case, ahead of governments on this issue.

      One issue is the high capital investment in power plants and distribution networks (smart grids etc) - and therefore the timing of shutting down ageing setups and replacing them with modern clean energy generators. If governments created the right policy framework older plants would be shut down sooner and the shift to clean energy would happen even more quickly.

      Australia's Climate Commission argues we've got till about 2020 to sort things out - that is, to set on a path to rapidly reduce fossil fuel burning etc. Here are their "Critical Decade" reports.

    2. Sou, your comment reagrding Watts being beyond rationality and morality is spot on. Such a pathetic, feeble-minded, nasty little bucket of bile.

  4. I've updated the article with a link to Nature GeoSciences' description of "Correspondence". (I previously and inadvertently looked at a description of same in another of their publications, which suggested peer review wasn't normal for correspondence.)

    Anyway, it says it's up to the editor whether or not it's peer reviewed - so maybe it was after all.

    1. Nature advised me the paper was peer reviewed before publication.

  5. I've a new question for all you climate sensitivity experts out there - how can the low end of the transient climate response be 0.9C? That seems awfully low.

    1. Another suspiciously low sensitivity (TCR/ECS) estimate heavily dependent on OHC data...

      OHC reconstructions are a work in progress. Sampling density (both area and depth) falls rapidly by the decade pre-2000. If OHC is under-estimated in the reconstructions (and this is a very real possibility indeed), sensitivity estimates using that data will be biased low.

      That's why you are correct to emphasise that such estimates need to be viewed in context with paleoclimate estimates, which by their very nature are more complete.


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