When non-news becomes news

Today many people are surprised that The Times turned non-news into news by putting it on their frontpage: the fact that a paper by Lennart Bengtsson was rejected by Environmental Research Letters. Rejections of papers happens hundreds of times a day, so why put it on the frontpage? Well, the answer is simple, because it fits into a larger “story”. The larger story of course is that Bengtsson accused the climate science community of McCarthyism.

Bengtsson himself is feeding this larger story by saying in the article:

Lennart Bengtsson, a research fellow at the University of Reading and one of the authors of the study, said he suspected that intolerance of dissenting views on climate science was preventing his paper from being published. “The problem we now have in the climate community is that some scientists are mixing up their scientific role with that of a climate activist,” he added.

Non-news becoming news happens all the time in the media, this is how they work. When they smell there is an “affair”, tiny things suddenly get promoted to the frontpage. This happened after climategate as well. Suddenly it was news that AR4 wrongly claimed that Himalayan glaciers would be gone in 2035. I am convinced that without climategate all these other IPCC “gates” wouldn’t have been picked up by the media.

The Dutch journalist Tomas Vanheste was surprised how good this worked. He discovered a minor error in the WGII AR4 report – about the part of The Netherlands that is lying below the sea level. But after Himalaya gate this was suddenly enough to have a sea level gate. It’s all hyperbole but climate “activists” use this in their favor most of the days when the media is eager to exaggerate their latest findings:

It’s All Over: Melting of Western Antarctic Ice Sheet Unstoppable, NASA Says. Read more at http://indiancountrytodaymedianetwork.com/2014/05/14/its-all-over-melting-western-antarctic-ice-sheet-unstoppable-nasa-says-154868


This time IOP, the publisher of ERL replied quickly and complained about the non-news becoming news:

“With current debate around the dangers of providing a false sense of ‘balance’ on a topic as societally important as climate change, we’re quite astonished that The Times has taken the decision to put such a non-story on its front page.

I wish publishers and/or scientists were always so keen to correct decisions of the media, e.g. in case scientific claims are exaggerated.

Anyway, we now know a little more about the rejected paper of Bengtsson and four colleagues because IOP released one of the negative referee reports. This shows that the paper has a lot of similarities with the Lewis/Crok report. The reviewer starts with this:

The manuscript uses a simple energy budget equation (as employed e.g. by Gregory et al 2004, 2008, Otto et al 2013) to test the consistency between three recent “assessments” of radiative forcing and climate sensitivity (not really equilibrium climate sensitivity in the case of observational studies).
The study finds significant differences between the three assessments and also finds that the independent assessments of forcing and climate sensitivity within AR5 are not consistent if one assumes the simple energy balance model to be a perfect description of reality.

In our report we also describe the energy budget method. We actually favor it and claim it currently gives the best indication of the climate sensitivity of the current climate. Nic Lewis now defends this position in the Climate Dialogue that the Dutch institutes PBL, KNMI and myself have set up about this topic.

Lewis and I were criticised for publishing our report at GWPF instead of in a peer reviewed journal. Lewis has published in peer reviewed journals (and even I have one publication) and will do so again so we are not against that. We were and are convinced though that such a long analysis of parts of an IPCC report is not regarded as new science and will therefore be rejected. The referee report of the Bengtsson paper also suggests this:

The overall innovation of the manuscript is very low, as the calculations made to compare the three studies are already available within each of the sources, most directly in Otto et al.

So one may conclude that we see here peer reviewed evidence that our report wasn’t fit for a peer reviewed journal as well.

The referee report contains some awful language that reminds us of the let’s not give fodder to the skeptics remarks in some climategate emails:

Summarising, the simplistic comparison of ranges from AR4, AR5, and Otto et al, combined with the statement they they are inconsistent is less then helpful, actually it is harmful as it opens the door for oversimplified claims of “errors” and worse from the climate sceptics media side.

These kind of motivations should have no place in a reviewer’s report and if I were the reviewer I would have been unhappy to make my report public like IOP now did.

Steve McIntyre has some interesting observations about the reviewer’s report as well noting that the main shortcoming/error of the paper seems to be the fact that it compared observations with models where “no consistency was to be expected in the first place”. McIntyre:

Thus, the “error” (according to the publisher) seems to be nothing more than Bengtsson’s expectation that models be consistent with observations. Surely, even in climate science, this expectation cannot be seriously described as an “error”.



New Climate Dialogue about climate sensitivity

Today – after a long pause – a new Climate Dialogue has started about climate sensitivity and transient climate response. This of course is a highly relevant topic. Equilibrium climate sensitivity (ECS) and especially the transient climate response (TCR) largely determine how much warming we can expect this century.

Climate Dialogue is a platform for discussions between invited climate scientists on controversial climate topics. They represent a range of views. Discussions are strictly moderated and should be on topic. Last year we did four Climate Dialogues, about arctic sea ice, long-term persistence, regional climate models and the hot spot in the tropics.

We are very happy that a few key players in the debates surrounding climate sensitivity have agreed to participate in this Climate Dialogue. John Fasullo of NCAR is well-known for his publications with Kevin Trenberth about the role of the natural variability and the oceans in the recent hiatus. James Annan, who recently moved back to the UK after working for many years in Japan, has also published a lot about climate sensitivity and is also frequently blogging about it. Finally Nic Lewis is a relative newcomer in climate science. After a career in the financial sector he recently became a climate scientist, focusing on climate sensitivity. He published a few papers about climate sensitivity, one with a group of IPCC lead authors.

A Sensitive Matter
Some readers will remember that Nic Lewis and I published a GWPF report in March of this year with the title A Sensitive Matter: How the IPCC hid the good news on global warming. One of the main conclusions of our report was that observationally based estimates for ECS and TCR (based on the so-called instrumental period, say 1850-2014) are “superior” at the moment and are to be preferred over estimates from GCMs or paleorecords.

We claim that these “observational” estimates indicate best estimates for ECS that are close to the lower boundary of the likely range in several IPCC reports which is 1.5–4.5°C. We give an “observational” likely range of 1.25-3°C with a best estimate of 1.75°C. This is substantially lower than the average ECS value of the CMIP5 models which is more than 3°C.

IPCC gave a best estimate of 3°C in AR4 but none in AR5. This lack of a best estimate was only mentioned in a footnote in the SPM. Lewis and I wrote in our report that the discrepancy between the observationally based best estimate and the model based best estimate was likely the main reason why IPCC didn’t give a best estimate this time. So IPCC on the one hand says climate sensitivity will likely be anywhere between 1.5–4.5°C and no best value can be given. But when doing projecetions AR5 relies (also in the Working Group II and III reports) on climate models that have an average climate sensitivity of 3.2°C.

So it is really important to find out where the discrepancy between the observationally based and model based estimates comes from. This will certainly be a crucial question in this Climate Dialogue.

Lewis in his guest blog repeated his likely range for ECS being lower than that of AR5:

The soundest observational evidence seems to point to a best estimate for ECS of about 1.7°C, with a ‘likely’ (17-83%) range of circa 1.2–3.0°C.

Annan agrees that the observational record points towards lower values for ECS and TCR. But nevertheless he comes up with slightly larger value for the best estimate than Lewis:

The recent transient warming (combined with ocean heat uptake and our knowledge of climate forcings) points towards a “moderate” value for the equilibrium sensitivity, and this is consistent with what we know from other analyses. Overall, I would find it hard to put a best estimate outside the range of 2-3°C.

Fasullo did not yet give his preferred likely range but he emphasized in his guest blog that lowering the lower boundary of the likely range in AR5 to 1.5°C (was 2°C in AR4) maybe was justified at the time but not any longer:

In short, I argue that although IPCC’s conservative and inclusive nature may have justified such a reduction at the time of their report, the evidence accumulated in recent years argues increasingly against such a change. Lees verder…


Presentatie “Een gevoelige kwestie: hoe het IPCC goed nieuws over klimaatverandering verborg”

Op donderdag 6 maart a.s. van 10:00 uur tot 13:00 uur presenteert de Groene Rekenkamer in Nieuwspoort (Den Haag) in samenwerking met de Britse Global Warming Policy Foundation het rapport “Een gevoelige kwestie: hoe het IPCC goed nieuws over klimaatverandering verborg“. De auteurs van dit rapport, wetenschapsjournalist Marcel Crok en de Britse zelfstandig onderzoeker Nic Lewis zullen een uitgebreide toelichting geven.

Goed nieuws over het klimaat, wat het IPCC u naliet te vertellen
In september 2013 verscheen het eerste en belangrijkste deel van het vijfde IPCC-rapport (AR5). De hoofdboodschap luidde dat het IPCC er nu 95% zeker van is dat tenminste de helft van de opwarming sinds 1950 door de mens veroorzaakt is. Een slimme formulering van het IPCC want deze op zichzelf weinig zeggende claim is in de media geïnterpreteerd als “we zijn er nu 95% zeker van dat er een groot klimaatprobleem is dat door CO2 wordt veroorzaakt.”

Tegelijkertijd voelt het IPCC zich minder zeker over misschien wel de belangrijkste parameter in de hele klimaatdiscussie: klimaatgevoeligheid. Dit is per definitie de opwarming als gevolg van een verdubbeling van de CO2-concentratie. Hoe gevoelig het klimaat is bepaalt hoeveel opwarming we in de toekomst zullen krijgen bij de gestaag oplopende CO2-concentratie in de atmosfeer.

Klimaatonderzoekers gaan er al dertig jaar vanuit dat de aarde bij een verdubbeling van de CO2-concentratie ongeveer drie graden zal opwarmen. Het vijfde IPCC-rapport gaf echter geen beste schatting voor klimaatgevoeligheid maar alleen een ruime marge van 1,5 tot 4,5 graden Celsius. Die marge is ook al ruim dertig jaar onveranderd.

De Nederlandse wetenschapsjournalist Marcel Crok, auteur van het boek De Staat van het Klimaat, en de Britse zelfstandig onderzoeker Nic Lewis, waren expert reviewers van het vijfde IPCC-rapport. Lewis publiceerde in de afgelopen jaren enkele wetenschappelijke artikelen over klimaatgevoeligheid. Lewis en Crok werkten in het afgelopen halfjaar aan een uitgebreide reactie op het IPCC-rapport.

Zij constateerden dat het IPCC-rapport alle ingrediënten bevat om te kunnen concluderen dat de klimaatgevoeligheid aanzienlijk lager is dan de klimaatwetenschap al decennia denkt. Het IPCC trok die conclusie echter niet.

In een rapport dat in Engeland op 6 maart a.s. verschijnt bij de Global Warming Policy Foundation en in Nederland bij De Groene Rekenkamer, concluderen Lewis en Crok dat de beste schatting voor klimaatgevoeligheid dicht tegen de ondergrens van de IPCC-range van 1,5 tot 4,5 graden Celsius ligt.

Lewis en Crok laten ook zien dat ons waarschijnlijk aanzienlijk minder opwarming te wachten staat dan het IPCC verwacht op basis van klimaatmodellen. Bij de twee middelste scenario’s van het IPCC blijft de opwarming in 2100 op of zelfs onder de internationale tweegradendoelstelling. Het rapport is dus zeer relevant voor beleidsmakers en politici.

Het Nederlandse rapport is een vertaling van het rapport “A Sensitive Matter – How the IPCC Buried Evidence Showing Good News About Global Warming“, dat is uitgegeven door de Global Warming Policy Foundation. Er bestaat ook een kortere Engelse versie van het rapport getiteld “Oversensitive – How The IPCC Hid The Good News On Global Warming“. Beide rapporten zijn vanaf donderdag 6 maart a.s. gratis te downloaden op de website van de Global Warming Policy Foundation, http://www.thegwpf.org/category/gwpf-reports/ en op de website van de Groene Rekenkamer, http://www.groenerekenkamer.nl/rapporten/

De vertaling voor de Nederlandse editie is gemaakt door Marcel Crok en is eveneens vanaf 6 maart a.s. via bovenstaande link van DGRK te downloaden.

Belangstellenden die interesse hebben in het bijwonen van de persconferentie met aansluitend de presentatie worden verzocht zich per email aan te melden bij kantoor@groenerekenkamer.nl

Om de hoge kosten van deze bijeenkomst enigszins te dekken vragen we van bezoekers een toegangsprijs van € 10,- per persoon. U kunt bij de ingang van de zaal contant afrekenen. Donateurs van de Groene Rekenkamer en vertegenwoordigers van de media hebben vrij toegang.


Nieuwsuur over voetnoot 16

[Update na de uitzending]
Ok, het item zat redelijk in elkaar. Het voornaamste probleem voor de kijker was dat het leek of ik reageerde op Pachauri en hij op mij terwijl we het over verschillende zaken hebben. Pachauri had het over de claim in het IPCC-rapport die zegt dat de IPCC-auteurs er nu 95% zeker van zijn (expert judgement) dat meer dan de helft van de opwarming sinds 1950 door de mens komt.
Mijn reactie daarop – die niet werd uitgezonden – is dat die 95% zekerheid op zichzelf niet zoveel zegt. Je kunt er bv 95% zeker van zijn dat de mens een klein beetje opwarming veroorzaakt en dan hoeft er überhaupt geen sprake te zijn van een probleem. Dus, zeg ik, is de belangrijkere vraag of de mens veel opwarming veroorzaakt met de uitstoot van broeikasgassen of weinig of iets ertussen in. En daar gaat die voetnoot over. Die voetnoot zegt dat het IPCC er nog niet over uit is of het veel is of weinig of iets ertussen in. Dat daar geen overeenstemming over is. Nic Lewis en ik zullen vervolgens in ons rapport laten zien dat de “beste” methodes erop wijzen dat het relatief weinig is en aan de onderkant van de range van waarden zit die het IPCC hanteert. [Einde update]

Nieuwsuur besteedt zo meteen tussen 22 en 23 uur zowaar weer eens aandacht aan klimaat. Aanleiding is het bezoek Rajendra Pachauri en andere hooggeplaatste IPCC-functionarissen deze week aan Nederland in verband met het zogenaamde Synthesis-report, het rapport dat een synthese maakt tussen de vuistdikke rapporten van achtereenvolgens Werkgroep I, II en III.

Nieuwsuur interviewde Pachauri en aansluitend Wilco Hazeleger en ondergetekende. Ik heb geprobeerd uit te leggen dat achter een voetnoot in de Summary for Policy Makers van het vijfde IPCC-rapport een heel verhaal schuil gaat. Sterker nog, onder andere die voetnoot is aanleiding geweest voor mij en de Brit Nic Lewis om een eveneens behoorlijk lijvige reactie op het IPCC-rapport te schrijven. Dat rapport komt binnenkort uit in zowel het Engels (bij de Global Warming Policy Foundation) als in het Nederlands (bij de Groene Rekenkamer). De submissies van Nic Lewis en mij aan de Britse Energy and Climate Change Committee geven trouwens al een aardig beeld van onze bevindingen.

Zoals de aankondiging op de website van Nieuwsuur laat zien roept Pachauri tot meer urgentie. Lewis en ik laten in ons rapport juist zien dat het vijfde IPCC-rapport alle ingrediënten bevat om tot de conclusie te komen dat het klimaatprobleem juist aanzienlijk minder urgent is. Het IPCC zelf heeft die conclusie echter niet getrokken (en daarom doen wij het in ons rapport) en deze netelige kwestie afgedaan met die nu al beruchte voetnoot 16 in de SPM.



Nic Lewis’ submission to the AR5 inquiry

All the written submissions to the UK Energy and Climate Change Committee are now online. Many interesting things to read. Lots of critical submissions. Judith Curry calls Nic Lewis’ contribution a “tour de force” which it really is. Some readers here might know that Nic and I have been working for the past few months on a report for the Global Warming Policy Foundation about how AR5 dealt with climate sensitivity. His submission is a nice introduction/summary of our report which hopefully will be published in January. Below is Nic’s submission. I strongly encourage readers to read it in full.


Written evidence submitted by Nicholas Lewis

Credentials and statement of interests

I am an independent, self-funded climate science researcher. In recent years I have specialised in the key area of climate sensitivity. My work has been published in the peer reviewed literature and is cited and discussed in the IPCC’s Fifth Assessment Report (AR5). I was an expert reviewer of AR5.

Introduction and summary

  1. The terms of reference for this inquiry ask various questions. I address the following questions; my related conclusions are italicised.
  • How robust are the conclusions in the AR5 Physical Science Basis report (AR5-WG1)?
    In the central area of climate sensitivity, they are misleading. The substantial divergence between sensitivity estimates from, on the one hand, satisfactory studies based on instrumental observations over an extended period and, on the other hand, from flawed studies and from computer models was not brought out.
  • Does the AR5 address the reliability of climate models?
    Not adequately. Shorter-term warming projections by climate models have been scaled down by 40% in AR5, recognising that they are unrealistically high. But, inconsistently, no reduction has been made in longer term projections.
  • Do the AR5 Physical Science Basis report’s conclusions strengthen or weaken the economic case for action to prevent dangerous climate change?
    Although the conclusions fail to say so, the evidence in AR5-WG1 weakens the case since it indicates the climate system is less sensitive to greenhouse gases than previously thought. Lees verder…

Submission to AR5 inquiry

The UK Energy and Climate Change Committee invited anyone with interest in the AR5 report to submit answers on a long list of questions. The deadline has now passed and several people have already made their contribution public (Richard Tol, Paul Matthews, Mike Haseler). As sooner or later all the submissions will be public anyway I have decided to do the same. My submission follows below and can also be downloaded as a pdf here.

Energy and Climate Change Committee inquiry into AR5
Written submission by Marcel Crok

Credentials and statement of interests

I am a Dutch freelance science writer based in Amsterdam. Since 2005 I specialised in the global warming debate. In 2005 as an editor of the Dutch monthly popular science magazine Natuurwetenschap & Techniek (recently this has become the Dutch edition of New Scientist) I published a long and critical article about the infamous hockey stick graph featuring the criticism of Stephen McIntyre and Ross McKitrick. Many of the issues described in that article came back in the Climategate emails.
I published a critical book in 2010 that focused on the third and fourth assessment reports of the IPCC (TAR and AR4). The Dutch Ministry of Infrastructure and the Environment then gave me funding to critically review AR5 as an expert reviewer.
Since Climategate I am in favour of a more constructive interaction between climate scientists with opposing views. Late 2012 the Ministry of Infrastructure and the Environment funded an international discussion platform, ClimateDialogue.org, that organises constructive dialogues between climate scientists with opposing views. This has been set up by the leading Dutch climate related institutes KNMI and PBL and myself. [1] We cover controversial topics and invite scientists with a range of views.
In 2013 I was co-author of my first peer reviewed paper (describing a European temperature shift in 1988).

How robust are the conclusions in the AR5 Physical Science Basis report?
To answer this question is beyond the scope of this inquiry I would say. However your own introduction provides a good start to deal with it. You wrote: “The report concluded that, ‘it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.’ But it reduced the lower bound for likely climate sensitivity and for the first time did not publish a best estimate of it because of lack of agreement.”
It’s good that you picked up this apparent paradox. AR5 itself focused on the 95% certainty that humans are the cause of most (>50%) of the warming since 1950. Most media outlets brought this as the major news of AR5 writing things like ‘how much more certainty do you want (before you act)?’.
However this interpretation of the 95% claim is misleading. In a sense the 95% claim of AR5 (itself a result of expert judgment and not some sort of mathematical calculation) is a no-brainer.
To understand this we focus on this other important parameter, climate sensitivity (the rise in global temperature after a doubling of the CO2 concentration). Recently several papers have been published estimating climate sensitivity from observational data since 1850. These studies assume that almost all of the warming since 1850 is due to greenhouse gases. These papers then come up with best estimates for climate sensitivity in the range of 1.5 to 2.0°C, considerably lower than the best estimate of 3.0°C that IPCC has presented in all their assessment reports so far.
So claiming that at least 50% of the warming since 1950 is due to humans is meaningless. The much more important question is whether the contribution of greenhouse gases to warming is big or small. AR5 has all the ingredients to conclude that the contribution is much smaller than we have thought for the last three decades. But by not giving a best estimate for climate sensitivity it failed to communicate this important message. So IPCC failed to give policy makers its most important conclusion. And IPCC only dealt with this important decision in a footnote in the Summary for Policymakers (SPM).
The 95% claim also tells you nothing about the seriousness of the climate issue. The 95% can be completely in accordance with there being no climate problem at all. IPCC failed to explain this clearly and journalists didn’t pick it up.
To conclude: the 95% claim of AR5 has been misinterpreted by most people, including policy makers and the media as the final proof that we have a huge anthropogenic climate problem. The claim itself proves no such thing and is in fact pretty meaningless.
Although it seems contradictory, there is in itself no conflict between the increasing certainty (the 95% attribution claim) and not giving a best estimate for climate sensitivity (less certainty). The 95% claim is just very conservative and tells you little about the seriousness of the climate issue. Lees verder…


Met Office fails to acknowledge their model is overly sensitive

Met Office responded to David Rose’s latest contribution to the debate. In Rose’s article there is a box about Nic Lewis’ rather technical critique of the Met Office report on the pause, about which I blogged the other day. In their reply the Met Office notes that it “will require time to provide as helpful a response [to Nic lewis] as possible, so further comment will be released in due course. But right after that they claim:

The article states that the Met Office’s ‘flagship’ model (referring to our Earth System Model known as HadGEM2-ES) is too sensitive to greenhouse gases and therefore overestimates the possible temperature changes we may see by 2100.

There is no scientific evidence to support this claim. It is indeed the case that HadGEM2-ES is among the most sensitive models used by the IPCC (something the Met Office itself has discussed in a science paper published early this year), but it lies within the accepted range of climate sensitivity highlighted by the IPCC.

Equally when HadGEM2-ES is evaluated against many aspects of the observed climate, including those that are critical for determining the climate sensitivity, it has proved to be amongst the most skilful models in the world.

The information that the HadGEM2 model is too sensitive came from Nic lewis’ article. The red bar in the figure below is the ECS of HadGEM2. It’s clearly obvious that it’s higher than the ECS of all other models and even higher than the 95% upper range of the CMIP5 models.

Nic Lewis replied to the Met Office as follows:

I would like to comment on the statements:

“The article states that the Met Office’s ‘flagship’ model (referring to our Earth System Model known as HadGEM2-ES) is too sensitive to greenhouse gases…”

and (referring to the sensitivity of HadGEM2-ES):

“it lies within the accepted range of climate sensitivity highlighted by the IPCC.”

Table 1 in Forster et al, 2013 ( Evaluating adjusted forcing and model spread for historical and future scenarios in the CMIP5 generation of climate models. J. Geophys. Res., doi:10.1002/jgrd.50174) gives the equilibrium climate sensitivity (ECS) of HadGEM2-ES as 4.59°C.

The IPCC stated in its 4th Assessment Report (WG1: Box 10.2): “we conclude that the global mean equilibrium warming for doubling CO2, or ‘equilibrium climate sensitivity’, is likely to lie in the range 2°C to 4.5°C.” It gave no other range for ECS in that report, nor has it as yet changed that range.

I therefore fail to understand how the Met Office can claim that HadGEM2-ES lies within the accepted range of climate sensitivity highlighted by the IPCC.

Nic Lewis

The Met Office would have done itself a favour if they had done their homework first before sending out another unjustified claim.




Nic Lewis’ response will hit the Met Office like a boomerang

Nic Lewis has published a lengthy and quite technical response on a recent Met Office report, see the posts at Bishop Hill and Judith Curry. His response will hit the Met Office like a boomerang.

Why like a boomerang? In July the Met Office published three reports about the ‘pause’. In the third and I would say most important one they looked at the implications of the pause for estimates of climate sensitivity and projections of future warming. Their key conclusions were (see their concluding remarks):

Despite the fact that the first decade of the 21st century has been a period during which there was very little global mean surface temperature rise, the range of TCR [Transient Climate Response, MC] estimates from the CMIP5 models lies within the TCR derived from observations, including this period.

When projections from the newer CMIP5 models are combined with observations, and specifically including the surface temperatures from the last 10 years, the upper bound of projections of warming are slightly reduced, but the lower bound is largely unchanged. More importantly, the most likely warming is reduced by only 10%, indicating that the warming that we might previously have expected by 2050 would be delayed by only a few years.

In simpler words, Met Office claims the recent pause in global warming has had little impact on estimates of climate sensitivity and future warming and models and observations largely agree with eachother. Met Office backed this up with several figures. Below I show their figure 5, showing estimates for Equilibrium Climate Sensitivity (ECS), which is the warming due to a doubling of the CO2 concentration, after the system has reached a new equilibrium.

Met Office figure 5

Otto et al is a recently published study that estimated climate sensitivity from observations. Visually the message is clear: there is a huge overlap between Otto et al (observations), CMIP3 and CMIP5 (the models) and palaeo estimates. Models therefore are ‘consistent with’ the observations, which is important to have faith in their projections of future climate. Nic Lewis was a coauthor of the Otto et al paper together with a large group of lead authors of the upcoming AR5 report. Lewis wrote the response in a personal capacity.

Now to make a long introduction short, here is Lewis’ adjusted version of the Met Office figure 5:

Lewis added other recent estimates of ECS based on observations (Aldrin, Lewis, Masters), he removed the palaeo estimates (as these are far too uncertain and contain “little information”) and he used flasks to show the 5-95% range of the distribution. The black bars are Lewis’ best estimates (medians). The white bars are the Met Office best estimates, for CMIP3 and 5 Met Office used the means instead of the medians.

The “boomerang” is the red bar on top of the CMIP5 distribution. This is the ECS of Met Office’s own flagship HadGEM2-ES model. As one can clearly see Met Office’s own model is not only far more sensitive than the observations suggest but even more sensitive than all other models. As Lewis put it:

And HadGEM2-ES has an ECS that exceeds not only the 95% bound from Otto et al but also that from two other recent observationally-based studies. Moreover, both the TCR and the ECS of HadGEM2-ES exceed the 95% bounds derived not only from CMIP3 models but also from CMIP5 models other than HadGEM2-ES.

So the Met Office model’s best estimate lies outside the range of both the observations and all the other models. It is a clear outlier. Met Office failed to disclose this in their own report, only showing the range of all the models in their figure 5 (and in other figures).

Relevance for the upcoming AR5 report
Although Lewis’ response is directed at the Met Office report, his piece is also highly relevant for the upcoming AR5 report. In an article today in the Wall Street Journal Matt Ridley quotes from the leaked SPM of AR5 (my bold):

Specifically, the draft report says that “equilibrium climate sensitivity” (ECS)—eventual warming induced by a doubling of carbon dioxide in the atmosphere, which takes hundreds of years to occur—is “extremely likely” to be above 1 degree Celsius (1.8 degrees Fahrenheit), “likely” to be above 1.5 degrees Celsius (2.4 degrees Fahrenheit) and “very likely” to be below 6 degrees Celsius (10.8 Fahrenheit). In 2007, the IPPC said it was “likely” to be above 2 degrees Celsius and “very likely” to be above 1.5 degrees, with no upper limit. Since “extremely” and “very” have specific and different statistical meanings here, comparison is difficult.

Still, the downward movement since 2007 is clear, especially at the bottom of the “likely” range. The most probable value (3 degrees Celsius last time) is for some reason not stated this time.

Apparently IPCC is planning (countries will negotiate about the final text in Stockholm later this month) to lower its likely lower bound for ECS from 2.0 in AR4 to 1.5 in AR5. By doing this the median estimates based on observations shown in the Lewis’ figure above fall into the likely range. So this rightly reflects the recent literature.

However, less assuring is that Ridley reports that in the draft SPM “The most probable value (3 degrees Celsius last time) is for some reason not stated this time”. As can be seen clearly in the Lewis’ figure, all the recent most probable values based on observations lie between 1.5 and 2. The central estimate of the models is 3. Or as Lewis put it into his conclusions:

Observationally-based median estimates for TCR and ECS are often comparable to the bottom of model-based uncertainty ranges.

This means that only the least sensitive models come close to the observations. Now this generates a big dilemma for the IPCC authors which could explain why so far – in their draft SPM – they failed to mention a best estimate for ECS. Recently there has been is a growing discrepancy between observationally based estimates and model based estimates for ECS. Should IPCC give equal weight to both methods? Should IPCC average the central estimates of both methods (leading to a reduced new estimate of let’s say 2.5)? Or should they put most weight onto the observations? In the last case they should lower their best estimate to at least 2. That would be a spectacular result as the best estimates for ECS hardly changed at all since the 1979 Charney report.

I hope many countries (including my own) will urge the IPCC to publish a best estimate for ECS (like they did in AR4) or – in case not – to clearly explain why they decided not to mention it this time. I see this as one of the most if not the most important decision for the four day meeting in Stockholm. On 27 September we will know the answer.


Sessie met Kamp opgepikt door Trouw

Trouw komt vandaag met maar liefst twee stukken (een zelfs op de voorpagina! en een op pag 12/13) over de klimaatsessie die Economische Zaken vorige week organiseerde voor minister Kamp. De stukken putten met name uit de notitie die PBL/KNMI schreef ter voorbereiding op de sessie. Die stukken plus de presentaties van Bart Strengers en Wilco Hazeleger staan nu ook online.

Mijn naam is weliswaar genoemd in Trouw maar uit mijn stuk is niet of nauwelijks geciteerd. Trouw zet stukken tegenwoordig niet meer gratis online en ik zal daarom de stukken zeker vandaag nog niet integraal online zetten. Het stuk op de voorpagina begint als volgt:

Kamp wil feiten over het klimaat

Nieuwe minister hoopt zin en onzin te scheiden zodat hij weet waarop hij beleid moet baseren

Minister Henk Kamp (economische zaken) wil af van de controverse tussen klimaatsceptici en wetenschappers over de opwarming van de aarde. In een vertrouwelijke sessie met deskundigen heeft hij getracht de zin en de onzin in het klimaatdebat te scheiden, als basis voor nieuw beleid.

Kamp is sinds kort verantwoordelijk voor het klimaatbeleid. Wetenschappers zijn het over het algemeen eens over de ernst van de opwarming van de aarde, maar in het maatschappelijk debat worden de uitkomsten van onderzoek betwist. Kamp wil weten welke argumenten in de discussie op feiten zijn gebaseerd, en welke op fictie. Hij vroeg vertegenwoordigers van het KNMI en het Planbureau voor de Leefomgeving (PBL) om presentaties te houden. Ook klimaatjournalist Marcel Crok, die vraagtekens zet bij de rol van CO2 bij de opwarming van de aarde, mocht zijn visie geven. Alle deelnemers hebben geheimhouding moeten beloven over het gesprek, maar publiceerden wel de door hen geleverde stukken.

De rest van het stuk op de voorpagina put uitsluitend uit de Notitie van het PBL/KNMI. In het tweede langere stuk wordt wel heel summier iets over sceptische argumenten gezegd. Bijvoorbeeld: Lees verder…


Afkoeling aerosolen echt kleiner

In mijn boek De staat van het klimaat schreef ik dat research sinds het vierde IPCC-rapport erop wees dat het afkoelende effect van aerosolen (aanzienlijk) kleiner is dan tot nu toe gedacht. Op pagina 118 staat:

Terwijl het opwarmende effect van roet dus op het lijstje opwarmende factoren moet, lijkt het afkoelende effect van aerosolen almaar kleiner te worden. Dat wil zeggen, kleiner dan de balken in afbeelding 8 suggereren. In 2009 publiceerde de Noor Gunnar Myhre een artikel in Science, waarin hij de koeling door het directe aerosoleffect naar beneden bijstelde.

Het indirecte aerosoleffect lijkt ondertussen helemaal op de helling te staan. De Amerikaanse klimaatonderzoeker Graeme Stephens van Colorado State University is nauw betrokken bij twee belangrijke satellietmissies van NASA: CloudSat en Calipso. Deze twee satellieten vliegen vlak achter elkaar aan en geven een ongekend scherp driedimensionaal beeld van wolken en aerosolen. Uit de metingen blijkt volgens Stephens dat het indirecte aerosoleffect vrijwel nul is.

Vooral de zeer lage schatting voor het indirecte aerosol effect (het effect van aerosolen op wolken) van Stephens baarde opzien. Stephens vertelde mij dat tijdens een interview dat ik met hem had in de zomer van 2009 in Fort Collins. Hij vertelde het bovendien in een Gewex-lezing in 2009, zie deze blog van Pielke. De onderzoekers van PBL en KNMI die mijn boek doorlichtten vroegen zelfs bij Stephens na of hij dat inderdaad gezegd had. Lees verder…




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