Did the IPCC just blink?

The wave of new evidence of low climate sensitivity, the existence of which is denied by the CCC's David Kennedy and downplayed by Julia Slingo, has presented the IPCC with a dilemma. They could try to bluff it out, an approach that could be terminal given the widespread reporting of the new science in the media. Alternatively they could 'fess up. This too could be extremely damaging, but perhaps might not be the end of them.

Being good bureaucrats they have gone for the option that is most likely to lead to their survival. At least that is what I surmise from a posting at the Economist, which has managed to get its hands on a table from the IPCC's Fifth Assessment Report. According to the article, a draft of the WG3 report reveals that

at CO₂ concentrations of between 425 parts per million and 485 ppm, temperatures in 2100 would be 1.3-1.7°C above their pre-industrial levels. That seems lower than the IPCC’s previous assessment, made in 2007. Then, it thought concentrations of 445-490 ppm were likely to result in a rise in temperature of 2.0-2.4°C.

Now of course, it's draft and its WG3, not WG1, so we have to be cautious. But there is at least a possibility that they are going turn down the alarm somewhat.

Chalk up another for low climate sensitivity

Nicola Scafetta has a new paper in Energy and Environment, which finds a figure for climate sensitivity of 1.35, some what lower than even the torrent of EBM papers over the last year or two.

Global surface temperature records (e.g. HadCRUT4) since 1850 are characterized by climatic oscillations synchronous with specific solar, planetary and lunar harmonics superimposed on a background warming modulation. The latter is related to a long millennial solar oscillation and to changes in the chemical composition of the atmosphere (e.g. aerosol and greenhouse gases). How- ever, current general circulation climate models, e.g. the CMIP5 GCMs, to be used in the AR5 IPCC Report in 2013, fail to reconstruct the observed climatic oscillations. As an alternate, an empirical model is proposed that uses: (1) a specific set of decadal, multidecadal, secular and millennial astronomic harmonics to simulate the observed climatic oscillations; (2) a 0.45 attenuation of the GCM ensemble mean simulations to model the anthropogenic and volcano forcing effects. The proposed empirical model outperforms the GCMs by better hind-casting the observed 1850-2012 climatic patterns. It is found that: (1) about 50-60% of the warming observed since 1850 and since 1970 was induced by natural oscillations likely resulting from harmonic astronomical forcings that are not yet included in the GCMs; (2) a 2000-2040 approximately steady projected temperature; (3) a 2000-2100 projected warming ranging between 0.3°C and 1.6°C , which is significantly lower than the IPCC GCM ensemble mean projected warming of 1.1°C to 4.1°C; (4) an equilibrium climate sensitivity to CO₂ doubling centered in 1.35°C and varying between 0.9°C and 2.0°C .

There is a preprint here. No doubt there will be the usual barrage of comments arguing that it should be ignored because it's in Energy and Environment. Let us see what a critique based on logic turns up.

David Kennedy on climate sensitivity

While on the train on the way down to London on Tuesday, I found myself reading David Kennedy's evidence to the Environmental Audit Committee inquiry into Carbon Budgets. Kennedy, readers are no doubt aware, is the chief executive of Deben's Committee on Climate Change.

Kennedy's remarks on climate sensitivity are, well, extraordinary:

If it was true that climate sensitivity estimates are now half what they were two years ago, that would raise a question. Is it still appropriate to be on this path, or should we take our foot off the pedal? On that specific issue I can tell you there is not any new evidence that makes us think differently about climate sensitivity. Some people would have you think that is the case, but if you look at the science, there is not a fundamental shift on that important issue of climate sensitivity, and I would not expect the IPCC, when it reports in October, to say the range for climate sensitivity has shifted significantly. Let’s see what they say. I would not expect them to say it has shifted. That is one of the things that will feed into our review, so we will be looking at the IPCC report before we do a report on the science and the international context in November, but the other thing is the call for evidence asks the specific question: is anything different, particularly on climate sensitivity as well as some of the other key things?

"..not any new evidence that makes us think differently about climate sensitivity"? Now that is a brazen statement if ever I saw one.

PCC throws out complaint against David Rose

The Press Complaints Commission has thrown out a complaint about David Rose's Mail on Sunday article about climate sensitivity. This is the text of their ruling.

The complainant, an environmentalist and the author of greenerblog.blogspot.com, was concerned that the newspaper had published an article on the subject of climate change – both in print and online – which contained a number of alleged inaccuracies, misleading statements and distortions in breach of Clause 1 (Accuracy) of the Editors’ Code of Practice.

Under the terms of Clause 1, “the press must take care not to publish inaccurate, misleading, or distorted information”; “a significant inaccuracy, misleading statement or distortion once recognised must be corrected promptly and with due prominence”; and “the press, whilst free to be partisan, must distinguish clearly between comment, conjecture and fact”.

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Vision of awfulness

The Vision Prize describes itself an "an online platform for communicating expert opinion on climate risk" and seems to be essentially a fairly basic online poll.

I was intrigued by the way its experts assessed climate sensitivity. The relevant question was what the effect on temperature relative to the year 2000 will be if carbon dioxide concentrations reach 550ppm (i.e the first doubling, expected around mid-century).

Here are the results:

The mode is 1.5-2.0°C. Given that this is temperatures relative to the present day, we have to add say 0.8°C to get the "climate sensitivity" figure, which would be 2.3-2.8°C. It seems to me that this figure is hard to justify if transient climate response is 1.3°C and effective climate sensitivity is 1.7°C, as seems likely from the empirical evidence.

Perhaps then the results are affected by climatologists who lie to promote political action.

Tom Chivers on climate sensitivity

The Telegraph's Tom Chivers has joined the throng of journalists who have covered the low climate sensitivity story. His take, which is pretty level-headed, is here.

There are some gripes, however:

• the suggestion that Otto is a an outlier - a single paper - is demonstrably nonsense. There are now many papers showing climate sensitivity less than 2°C.
• the suggestion that the heat is all going into the oceans is at best only "possible". All the studies with low climate sensitivity take ocean heat uptake into account (or, in Forster and Gregory's case use a methodology that is unaffected by it). Trenberth's new suggestion that the heat is below 2 km depth in the deep ocean is at best speculative.

That said, it's not a bad piece at all and is well worth a look.

Updated climate sensitivity estimates using aerosol-adjusted forcings and various ocean heat uptake estimates

The Otto et al. paper has received a great deal of attention in recent days. While the paper’s estimate of transient climate response was low, the equilibrium/effective climate sensitivity figure was actually slightly higher than that in some other recent studies based on instrumental observations. Here, Nic Lewis notes that this is largely due to the paper’s use of the Domingues et al. upper ocean (0–700 m) dataset, which assesses recent ocean warming to be faster than other studies in the field. He examines the effects of updating the Otto et al. results, extending from 2009 to 2012 and using different upper ocean (0–700 m) datasets, with surprising results.

Last December I published an article here entitled ‘Why doesn’t the AR5 SOD’s climate sensitivity range reflect its new aerosol estimates?‘ (Lewis, 2012). In it I used a heat-balance (energy-budget) approach based on changes in mean global temperature, forcing and Earth system heat uptake (ΔT, ΔF and ΔQ) between 1871–80 and 2002–11. I used the RCP 4.5 radiative forcings dataset (Meinshausen et al, 2011), which is available in .xls format here, conformed it with solar forcing and volcanic observations post 2006 and adjusted its aerosol forcing to reflect purely satellite-observation-based estimates of recent aerosol forcing.

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A whiff of the Sunday Sport

Having failed to reply to Matt Ridley's request to respond to Myles Allen's critique, Damian Carrington and his band of merry men have responded with another, but rather grubbier, attack in the same direction, this time from Nuccitelli.

Given that even Nuccitelli's co-authors at Skeptical Science have pointed to his misrepresenting those who disagree with him, and given the car crash of his article about Nic Lewis the other day, a reputable newspaper would steer clear. But when you haemorrhaging money, I guess the priorities are different.

Here's a paragraph from Nuccitelli's article:

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Oxford professors and the poor

Yesterday Myles Allen posted a highly personal attack on Matt Ridley. The Guardian has apparently failed to respond to Matt's requests to allow him to respond (I am reminded of their publication of Bob Ward's hit piece on me back in 2009, when it took days to get them to reply to me and weeks before the response was published). This being the case Matt has asked me to post the following:

Dear Professor Allen,

In your polemical Guardian article on Tuesday you produce no counter-arguments to my Times article. For example, you ask: "Is Ridley right that there is no actual evidence of harm as long as droughts, floods and storms are within historic variability?" You then do not answer that question. Well, am I right or not?

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ECS with Otto

Further to the last posting, and in particular the claim in the BBC article that the 2-4.5 range is largely unaffected by the Otto et al paper, here's my graph of ECS curves with the incorporation of the Otto et al results - both the full-range and the last-decade curves. These are shown in black.  As previously, the other studies are coloured purple for satellite period estimates, green for instrumental, and blue for paleoestimates. The grey band is simultaneously the IPCC's preferred range and the range of the climate models.

As you will see, it is fairly clear that the Otto et al results slot in quite nicely alongside the other recent low-sensitivity findings, with most of the density outside the range of the models. The IPCC's preferred range looks increasingly untenable.

Reactions to Otto et al

Updated on May 20, 2013 by Bishop Hill

Updated on May 20, 2013 by Bishop Hill

Updated on May 20, 2013 by Bishop Hill

Press reactions to the Otto et al paper vary from the sublime to the ridiculous.

Matt Ridley in the Times (£) points to the policy implications and notes that mitigation now looks like a pretty daft approach to take:

It is true that the “transient climate response” is not the end of the story and that the gradual warming of the oceans means that there would be more warming in the pipeline even if we stopped increasing carbon dioxide levels after doubling them. But given the advance of nuclear and solar technology, there is now a good chance we will have decarbonised the economy before any net harm has been done.

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New energy-budget-derived estimates of climate sensitivity and transient response in Nature Geoscience

This is a guest post by Nic Lewis. Please note that although the embargo on the paper was lifted at 6pm, at time of writing the paper itself had yet to appear on the Nature website. It should be at the link given below in the near future.

Readers may recall that last December I published an informal climate sensitivity study at Bishop Hill, here. The study adopted a heat-balance (energy budget) approach and used recent data, including satellite-observation-derived aerosol forcing estimates. I would like now to draw attention to a new peer-reviewed climate sensitivity study published as a Letter in Nature Geoscience, "Energy budget constraints on climate response", here. This study uses the same approach as mine, based on changes in global mean temperature, forcing and heat uptake over 100+ year periods, with aerosol forcing adjusted to reflect satellite observations. Headline best estimates of 2.0°C for equilibrium climate sensitivity (ECS) and 1.3°C for the – arguably more policy-relevant – transient climate response (TCR) are obtained, based on changes to the decade 2000–09, which provide the best constrained, and probably most reliable, estimates. The 5–95% uncertainty ranges are 1.2–3.9°C for ECS and 0.9–2.0°C for TCR. I should declare an interest in this study: you will find my name included in the extensive list of authors: Alexander Otto, Friederike E. L. Otto, Olivier Boucher, John Church, Gabi Hegerl, Piers M. Forster, Nathan P. Gillett, Jonathan Gregory, Gregory C. Johnson, Reto Knutti, Nicholas Lewis, Ulrike Lohmann, Jochem Marotzke, Gunnar Myhre, Drew Shindell, Bjorn Stevens, and Myles R. Allen. I am writing this article in my personal capacity, not as a representative of the author team.

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Hansen's scandalous interview

The Today programme also interviewed James Hansen on climate sensitivity this morning (see link below). This was an extraordinary performance by any standards.

Hansen opened with the most astonishing claim about global temperatures,

In the last decade it's warmed only about a tenth of a degrees as compared to about two tenths of a degree in the preceding decade.

a claim which completely contradicts Hansen's own GISTEMP dataset (H/T Ruth Dixon).There is a suggestion that he might have been referring to a land-only dataset, but this would still be grossly misleading since he says that land-only data overestimates trends.

Hansen also spoke of the climate sensitivity, making the bizarre claim that our understanding is based on  paleoclimate rather than models and speaking of the excellence of the data in this area. This is mind-boggling, since these datasets contain so little information that they can barely constrain the climate sensitivity at all. The weakness of the constraint provide by paleo data was noted by the IPCC in the last assessment report, and they decided to base the "consensus" figure largely on models - precisely the opposite of what Hansen said was done.

He also tried to blame the standstill on aerosols, ignoring the fact that the IPCC's best estimate now finds that their effect is small, and he described heat going into the oceans as "a detail" and "a diversionary tactic".

Quite disgraceful.

Hansen Today

Update on May 17, 2013 by Bishop Hill

The Carbon Brief provides further information. Apparently when Hansen said "the trend over the last decade", he meant "the trend in the 5-year running mean over the period 2000-10".

"Sex that I woman did not have with" are the words that spring to mind.

Today does climate sensitivity

BBC Radio's flagship Today programme covers climate sensitivity and features, among others, yours truly. I haven't heard it yet, but this is a holding post until I can find the audio.

Update on May 17, 2013 by Bishop Hill

The audio is here.

Lewis responds to Nuccitelli

Nic Lewis has left a comment under Dana Nuccitelli's astonishing article in the Guardian.

In his piece, Dana Nuticelli links to his earlier article "Climate Sensitivity Single Study Syndrome, Nic Lewis Edition" at a climate change/global warming blog he is associated with. As the author of the paper "An objective Bayesian, improved approach for applying optimal fingerprint techniques to estimate climate sensitivity" (Journal of Climate, in press) that Dana Nuticelli's earlier article is about, I would like to take this opportunity to put on record my rebuttals of a number of misrepresentations he made of my paper, to avoid any Guardian readers who follow the link being misled. I apologise in advance for the length of this comment.

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