Ik was enigszins verrast toen ik enkele maanden geleden benaderd werd door de journalisten Ruben Koerhuis en Petra Pronk van de website Weg met MVO. Zij wilden mij interviewen. Een blik op hun site laat zien dat tot nu toe vooral bekende namen uit de Trouw Duurzame 100 zijn geïnterviewd, zoals Marjan Minnesma, Jan Rotmans, Jan Peter Balkenende, Sylvia Borren (van Greenpeace). Maar ook Niek Jan van Kesteren (directeur VNO-NCW) en Wiebe Draijer van de SER.
De titel van hun site is verwarrend. Zij bedoelen ermee dat Maatschappelijk Verantwoord Ondernemen zo vanzelfsprekend wordt dat de term overbodig wordt. Vandaar het “weg met”. MVO gaat om meer dan alleen CO2 uiteraard maar uit de andere interviews blijkt dat CO2 wel een belangrijke rol speelt op dit moment. Zij gaven aan dat ze ook andere visies wilden laten horen en ik stemde derhalve in met het interview. De opnames waren tamelijk imponerend, met vier, vijf camera’s om me heen in een geblindeerde ruimte.
Hopelijk kan het interview bijdragen aan het maatschappelijk debat over klimaat, energie en MVO. Ik dank Petra en Ruben voor de tijd en moeite die ze erin gestoken hebben.
In Elsevier van deze week een uitgebreid interview met Richard Tol. De kop boven het artikel is dezelfde als die boven dit bericht. Het hele interview is de moeite waard. Ik pik er een paar citaten uit:
Volgens de samenvatting voor beleidsmakers van het IPCC is klimaatopwarming een catastrofe. Volgens u niet? Richard Tol: ‘Nee, het is zeker geen catastrofe. De aarde warmt wel op door stijgende uitstoot van broeikasgas CO2, maar het wetenschappelijk onderzoek naar de gevolgen ervan laat zien dat ze over het algemeen beheersbaar zijn. Al moeten we natuurlijk wel blijven opletten. (…)”
Over de stagnatie van de wereldwijde opwarming zegt Tol:
ELSEVIER Is het zo dat de temperatuur al achttien jaar niet stijgt? Tol: ‘Ja, in september kan ik tegen eerstejaarsstudenten zeggen dat de aarde sinds hun geboorte niets warmer is geworden. Vraag is hoe dat kan: niemand heeft het zien aankomen. Vaststaat wel dat de aarde opwarmt door uitstoot van CO2 en andere gassen, en dat de mens hieraan een bijdrage heeft geleverd.
‘Misschien is de invloed van de mens kleiner dan tot nu werd aangenomen, of die van de zon groter. Of de natuurlijke variatie in het klimaat is groter dan gedacht. Misschien warmt de aarde straks dubbel zo snel op. We hebben geen idee. Het is wel ongelukkig: het wordt zo heel moeilijk mensen te overtuigen dat klimaatverandering echt bestaat.’
Over klimaatbeleid in Nederland en het VK:
ELSEVIER Ziet u zichzelf als een pleitbezorger van klimaatbeleid? Tol: ‘Ik zie mezelf niet als activist in welke richting dan ook. Hooguit kan ik me weleens opwinden over de gebrekkige kwaliteit van het klimaatbeleid dat in Nederland of hier in het Verenigd Koninkrijk wordt gevoerd. Het kan veel efficiënter.’ ELSEVIER Hoe? Tol: ‘Het klimaatbeleid dat hier wordt gevoerd, kost heel veel geld, maar levert weinig op. Het heeft eigenlijk niets te maken met klimaat en alles met windmolens. Die windmolens creëren nauwelijks lagere CO2-uitstoot, maar wel veel oppositie tegen klimaatbeleid. Ze zijn lelijk. ’ ELSEVIER Nederland wil in 2050 klimaatneutraal zijn. Is dat haalbaar, denkt u? Tol: ‘Nee. Er zijn simpelweg geen goede oplossingen om de uitstoot in verkeer en landbouw terug te brengen. Je kunt automobilisten wel meer biodiesel en ethanol laten tanken, maar het is onderhand duidelijk dat die niet echt broeikasemissies reduceren.
Lees het hele interview in Elsevier of via Blendle. Het interview is overigens niet geschreven door Simon Rozendaal maar door economieredacteur Michiel Dijkstra.
Guest post by David Henderson, GWPF
Prologue: a resignation under duress
On 24 April 2014 I sent an email to an eminent meteorologist, Professor Lennart Bengtsson, inviting him to become a member of the Academic Advisory Council of the Global Warming Policy Foundation (GWPF), and three days later I was happy to receive a letter of acceptance; I duly added Bengtsson’s name to our list of Council members, and his acceptance was announced on the GWPF website.
On 1 May the Dutch journalist Marcel Crok published on his blog an interview with Bengtsson. He began by posing the question:Why did you join the GWPF Academic Council? Bengtsson’s response was as follows:
I know some of the scientists in GWPF and they have made fine contributions to science. I also respect individuals that speak their mind as they consider scientific truth (to that extent we can determine it) more important than to be politically correct. I believe it is important to express different views in an area that is potentially so important and complex and still insufficiently known as climate change.
Crok’s final question was:
Are you satisfied with the role that the GWPF has played so far? What could or should they do differently in order to play a more successful and/or constructive role in the discussions about climate and energy?
To which Bengtsson responded:
My impression is that this is a very respectable and honest organisation but I will be happy to reply to your question more in depth when I have got experience of it.
Much to the regret of me and my GWPF colleagues, Bengtsson decided, only two weeks later, to withdraw his acceptance of my invitation. In the letter of resignation that he sent to me, he referred to ‘enormous world-wide pressure put at me from a community that I have been close to all my active life’; and in a letter to colleagues, announcing his decision, he likewise alluded to ‘massive objections from colleagues around the world’.
Though only a few of these ‘massive objections’ have come my way, they presumably have a common theme. The critics typically hold that the GWPF is not a reputable organisation; that the favourable impressions of it which Bengtsson had formed, as voiced in his interview with Crok, were badly mistaken; and that for any professional person to accept to have links with it would be evidence, at best of serious misjudgement, and at worst of a lack of integrity. Hence the Bengtsson affair, and the resulting publicity, have focused attention on the role and work of the Foundation.
As one who has been closely associated with the GWPF from the outset, as chairman of the Council that Bengtsson was invited to join, I offer here a brief personal perspective on the issues thus raised, chiefly with a view to providing information. In doing so, I point to what I see as misconceptions by various commentators, both friendly and hostile. I focus first and chiefly on the work of the Council, but afterwards touch on the work and role of the Foundation as a whole. Lees verder…
Het FD heeft een nieuw online product opgezet, FD Energie Pro. De site is net online gegaan en vooralsnog is de content gratis te lezen. Karel Beckman van de Energy Post heeft als interim hoofdredacteur de eerste verhalen uitgezet. Hij vroeg mij of ik er als freelancer voor wilde schrijven en het toeval wilde dat ik een dag later Matt Ridley zou opzoeken op diens landgoed ten noorden van Newcastle. Beckman wilde graag een interview met hem en zodoende staat dit interview nu als een van de eerste verhalen online. Het verhaal is nu nog gratis integraal te lezen. Hier de intro:
Viscount Matt Ridley is politicus, auteur, journalist, klimaatcriticus, bioloog, natuurliefhebber, ex-bankier, en eigenaar van een steenkolenmijn. Maar hij is bovenal: rationeel optimist. Hij gelooft dat de mensheid dankzij steeds verdere specialisatie en handel een welvarende toekomst tegemoet kan zien. Daarbij is een efficënte energievoorziening onmisbaar – en die kan volgens Ridley niet komen van bronnen als windenergie en biomassa. Journalist Marcel Crok bezocht Matt Ridley op zijn landgoed in Noord-Engeland.
Lennart Bengtsson blijft de gemoederen bezig houden. Ik stuurde hem na zijn besluit uit de GWPF te stappen een lijst met tien vragen. Lastige vragen vermoedelijk want ik vind dat hij met meer details naar buiten zou moeten treden over de e-mails die hij ontving. Hoe dan ook, geen antwoord meer van Bengtsson, die eerder steeds heel snel antwoordde op e-mails. Op twitter gisteren werd gesuggereerd dat hij tijd nodig heeft. Ik vraag me af of dat de reden is van het niet reageren want dit weekend verscheen wel een uitgebreide reactie van zijn hand op een Zweedse website. Hans Labohm woonde een tijdlang in Stockholm en spreekt goed Zweeds en heeft het artikel vertaald. Dank Hans.
Paul Matthews heeft ook een helder overzicht gemaakt van de gebeurtenissen. De reactie van Judith Curry mag je zeker niet missen. Die wijst terecht op de hypocrisie in de klimaatgemeenschap. Van Greenpeace en WWF-medewerkers wordt het geaccepteerd dat ze lead author worden bij het IPCC, maar als een door de wol geverfde wetenschapper een onbetaalde adviesrol gaat vervullen bij de GWPF dan is de wereld te klein.
Hier het integrale stuk van Bengtsson:
Enige overpeinzingen over het klimaat en onze mogelijke toekomst
Op het blog van ‘Stockholms Initiativet’ schreef Lennart Bengtsson een ‘posting’ getiteld: ‘Några tankar om klimatet och vår möjliga framtid’. De vertaling daarvan volgt hier.
Zo, en geloof je nu in opwarming?
Zoals de meeste vaste bezoekers van dit blog zullen weten – maar nauwelijks degenen die zijn aangewezen op de reguliere Zweedse media – is er rond mij onlangs grote commotie ontstaan. Ik zal hier geen overzicht geven van de media–aandacht die dat heeft gekregen, maar in plaats daarvan proberen om mijn gedachten en handelingen in een breder perspectief te beschrijven.
Ik kan alleen maar zeggen dat ik enorme steun van collega’s, academici en het grote publiek in het Verenigd Koninkrijk, de VS en Duitsland heb gekregen. Ik voel me bijna een vrijheidsstrijder. Ik heb echter geen overdreven illusies want ik ken de macht van het establishment. Het is in ieder geval verheugend om kennis te maken met de liberale en open traditie van de Engels media. De Zweedse media lijken nog te verkeren in de tweede helft van de 19e eeuw, een situatie die we die kennen uit Strindberg’s ‘Röda rummet’ (De rode kamer). Lees verder…
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”.
Mijn eerste reactie op het boek en vooral de boekpresentatie van De Twijfelbrigade is in verkorte versie overgenomen door de website Groene Kwesties. Met de oprichter van deze site, Marco Ploeger, heb ik onlangs geluncht. We kwamen erachter dat we elkaar al kenden van een interdisciplinair vak bij milieukunde van de UvA.
Ik ben overigens nog niet erg opgeschoten in De Twijfelbrigade. Alle energie en aandacht gaat momenteel naar de actualiteit, de Bengtsson-affaire en Climate Dialogue.
Lennart Bengtsson this morning sent an email to Benny Peiser and David Henderson of the GWPF and cc to Hans von Storch and myself amongst others in which he announces his resignation from the GWPF. Bengtsson gave Von Storch permission to post the email on Klimazwiebel so apparently the content is no longer confidential. I think it would have been much more professional if there was first an official announcement from the GWPF, but this is as it is now. So here is the email:
Dear Professor Henderson,
I have been put under such an enormous group pressure in recent days from all over the world that has become virtually unbearable to me. If this is going to continue I will be unable to conduct my normal work and will even start to worry about my health and safety.
I see therefore no other way out therefore than resigning from GWPF. I had not expecting such an enormous world-wide pressure put at me from a community that I have been close to all my active life. Colleagues are withdrawing their support, other colleagues are withdrawing from joint authorship etc. I see no limit and end to what will happen. It is a situation that reminds me about the time of McCarthy.
I would never have expecting anything similar in such an original peaceful community as meteorology. Apparently it has been transformed in recent years.
Under these situation I will be unable to contribute positively to the work of GWPF and consequently therefore I believe it is the best for me to reverse my decision to join its Board at the earliest possible time.With my
This is a very unfortunate development. Bengtsson joined the Academic Advisory Council of the GWPF only two weeks ago. Now one wonders what the crimes of the GWPF are? What makes the GWPF so “bad” that Bengtsson is now regarded as so contaminated that co-authoring a paper with him is not acceptable anymore?
I hope Bengtsson will give much more details in the coming days to weeks about what happened exactly. What does he mean for example when he writes “Colleagues are withdrawing their support”?
This is very bad for the trustworthiness of climate science. Over and over again we as a society are told there is a consensus about CO2 and climate, that there is a large majority in the field etc. However what does that all mean if eminent scientists like Bengtsson are punished severely, only for the fact that he joined an advisory board? Why would one trust climate science if such enormous social pressure is going on?
GWPF statement here
Steve McIntyre responds here
Anthony Watts was about to cross post the 1990 interview I posted yesterday. He now did so together with the news about the resignation.
Support letter from David Gee.
Ben Webster in The Times with a reaction from Bengtsson.
Judith Curry’s reaction. Her first comments:
I will have much more to write about this in a few days. For now, I will say that I deeply regret that any scientist, particularly such a distinguished scientist as Bengtsson, has had to put up with these attacks. This past week, we have seen numerous important and enlightening statements made by Bengtsson about the state of climate science and policy, and science and society is richer for this. We have also seen a disgraceful display of Climate McCarthyism by climate scientists, which has the potential to do as much harm to climate science as did the Climategate emails. And we have seen the GWPF handle this situation with maturity and dignity.
Lennart Bengtsson recently joined the Academic Council of the GWPF. This generated quite some attention on blogs and in the media. I interviewed him, but also Hans von Storch on Klimazwiebel, Axel Bojanowski had a story in Der Spiegel (English version), and there was an article in the Basler Zeitung.
Bengtsson emphasized that he has always been a “sceptic”. In the interview with me he said:
I have always been sort of a climate sceptic. I do not consider this in any way as negative but in fact as a natural attitude for a scientist. I have never been overly worried to express my opinion and have not really changed my opinion or attitude to science.
We all know that in climate discussions climate scientists are quick to say “we are all sceptics” so such a remark says little about Bengtsson’s exact viewpoints. The renowned Dutch science writer Simon Rozendaal then sent me a copy of his interview with Bengtsson published on 27 October 1990 (!) in the Dutch weekly Elsevier (for which Rozendaal still works as a science writer).
We can now confirm that Bengtsson was pretty “sceptic” in 1990. Here is the full translated Elsevier article:
A cool blanket of clouds
Climate expert Bengtsson puts the threat of the greenhouse effect in perspective
Next week, a large conference on the global climate will be held in Geneva. The most important topic of discussion: the greenhouse effect. Many hold the opinion that our planet is warming by the increase in carbon dioxide and that a climate disaster is looming. Maybe so, says Lennart Bengtsson, Europe’s most important climate scientist. Or maybe not. Bengtsson doesn’t actually know for sure. It could go either way.
Lennart Bengtsson is so far not daunted by the looming climate disaster. He frowns when looking at the tierische Ernst with which the rest of the world embraces the prediction that the planet warms due to the increase in gases like carbon dioxide (CO2). ‘It would become serious if the atmospheric CO2 concentration would decrease. Thanks to the greenhouse effect Earth is a habitable place. Were its concentration to decrease, then mean temperatures would plummet far below freezing. That really would be a catastrophe.’
The Sweed, who appears and talks like Max von Sydow, is director of the European Center for Medium Range Weather Forecast in Reading (United Kingdom), which supports eighteen European national weather centers like Dutch KNMI with computer models and simulations. Soon he will become director of the Max Planck institute in Hamburg and thereby will be in charge of Europe’s most important greenhouse effect computer model. ‘Until now the greenhouse effect research has concentrated in the United States, but Europe is advancing.’
There is something strange about the greenhouse effect. Many scientists babble and publish about it, but few really understand its ins and outs. Most of them treat assumptions as were they facts. Suppose that it would become two degrees warmer, how much higher would the Dutch dikes have to become? Or: suppose that we want to reduce CO2 emissions and still maintain economic growth for not so strong economies of Poland, Greece, and China, how much would the emissions of the wealthy Netherlands have to decrease? For the question whether the underlying assumptions are actually correct, one has to ask climate experts like Bengtsson.
He emphasizes that the greenhouse excitement is founded in computer simulations. And that computer generated models are not complete nonsense. ‘If for example such a model starts with a globally uniform temperature, then within a few months of simulation one would start to see the tropics warming and polar regions cooling. Remove the Amazon and after some time it reappears due to the torrential tropical rains. Such general characteristics of the global climate are part of the models.’
However, the models provide insufficient insight. ‘They are too coarse. While weather predictions nowadays have grid sizes of 100 by 100 kilometer, climate models work on a 500 by 500 km grid. In addition, models have problems with clouds. They are not able to predict what effect clouds have and they cannot distinguish between high and low clouds, yet we know that this differentiation has important consequences.’ Many other important aspects are lacking. Some of those cannot be incorporated simply because they are not well understood. ‘For a large part of the emitted carbon dioxide we do not know where it stays.’
Would there be no clouds, everything would be simple. ‘With a clear sky, increasing carbon dioxide or methane would lead to a reduction of heat radiation from the earth to the atmosphere. In addition, water vapor would amplify the so-called greenhouse effect. If temperatures increase, more water evaporates and water vapor is a powerful greenhouse gas.’
However, clouds do exist. It is these fluffy tufts that diminish much of the commotion surrounding the climate disaster. Clouds cool because they reflect sunlight. On the ground we notice this when we’re in a shadow. At the same time clouds warm because they prevent heat radiation from directly escaping to space: ground frost nearly always occurs under cloud free conditions. The simple question as to whether clouds cool or warm the Earth was until recently unanswered, and this says a lot about the current state of meteorology.
Among climate experts the opinion that clouds cool Earth is gaining ground, Bengtsson observes. ‘There are recent satellite observations, as reported in the scientific magazine Nature, showing that clouds reduce the greenhouse effect. In particular low level clouds are efficient cooling agents.’
Theoretically, the greenhouse effect could even cause a cooling rather than a warming of Earth. ‘The cooling effect of clouds is five times as strong as the temperature increase due to a doubling of atmospheric CO2.’ There is even an amplification of this feedback. Bengtsson: ‘If it gets warmer, clouds become whiter and thereby reflect more solar radiation.’
Such feedbacks are hardly part of the computer models that predict the warming, according to Bengtsson. ‘Almost no model is capable of dealing with the behavior of clouds. The models builders claim they do, but when we redo the calculations that turns out not to be true.’
There are other problematic issues. Were climate to really warm, snow and ice would have to melt. That would result in additional warming because white surfaces reflect more sunlight. ‘This additional warming is not present.’ Maybe the largest omission in knowledge about climate are the oceans.’ In most models it is assumed that the ocean is fifty meters deep, which is an average. But there are parts of the oceans that are several kilometers deep. Those would slow any potential warming. You could hide thousand years of warming in the ocean.’
The one small meteorological detail from the enormous amount of uncertainties, ambiguities and question marks that has become better understood is that an increase of CO2 and some other gases potentially has a warming effect. And that is what politics is focusing on right now. Bengtsson: ‘What happens in the Atlantic Ocean could have bigger consequences, but nevertheless all attention is focusing on the greenhouse effect.’
Bengtsson believes that climate experts should not pretend to be more knowledgeable than they really are. ‘In case of the greenhouse effect there is an interaction between media, politics and science. Every group pushes the other groups. Science is under pressure because everyone wants our advice. However, we cannot give the impression that a catastrophe is imminent. The greenhouse effect is a problem that is here to stay for hundreds of years. Climate experts should have the courage to state that we are not yet sure. What is wrong with making that statement clear and loudly?’
The excitement of the last weeks has moved everything into high gear. A United Nations committee (the IPCC) has released a report at the end of August which suggests that there is a broad scientific consensus about the existence of the greenhouse effect. This already has had political ramifications in many countries. For example, halfway October hundreds of Dutch politicians, experts, civil servants and industrialists have been discussing in Rotterdam themes from the 1960s like whether and how the Netherlands could lead the way (again). And early November there will be a global conference in Geneva about the global climate.
Bengtsson thinks that the IPCC has been particularly actuated for political reasons. ‘The IPCC prediction that with a doubling of CO2 in the atmosphere the temperature on Earth would rise by two degrees should be taken with a grain of salt.’
Due to the lack of understanding a thermometer remains crucial. And it is not pointing in the direction of a doomsday. ‘The temperature over the Northern Hemisphere has decreased since about 1950. In some countries the eighties were very warm, but there are countries where this is not the case. On Greenland there is little to be seen of the greenhouse effect. It has been very cold during the last couple of years.’
‘If you talk to the greenhouse mafia about these observations, they provide some answers, but those are not real. There is no proper support for the claim that the greenhouse effect should already be visible. It is sometimes stated that the Southern Hemisphere is warming. But there are so few observational sites over there that it is very difficult to draw any definitive conclusions about the temperature in the Southern Hemisphere.’
Bengtsson is not the only climate expert who thinks that much of the excitement about the greenhouse effect is undue. Many of his colleagues have been rather uneasy about what happened after they opened Pandora’s box. They have become afraid, now that politicians, camera crews, pressure groups and environmental departments worldwide have thrown themselves at the climate disaster, to openly state that what they have declared may have been a bit premature.
Bengtsson: ‘Many of us feel rather uncomfortable with much of what has been claimed about the greenhouse effect. No one had been talking about it because temperatures had been slightly on the decline during the last 30 years. Only after Jim Hansen of NASA had put the issue back on the agenda after the warm summer of 1988 has it become part of the political agenda. In itself there is no problem with that. Looking hundreds of years ahead the greenhouse effect could become a serious problem. Some policies are obviously a clever thing to do: save energy, become less dependent on oil, those are good ideas. But one cannot oversell the greenhouse effect. There are many environmental problems that are much more urgent like that of the sulphur dioxide in Eastern Europe.’
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…