Comment on EER interview with Fritz Vahrenholt

Also published in European Energy Review (EER).

Greenhouse gases are responsible for warming, not the sun

Scientists working on climate on a daily basis must have been rather astonished by the interview with Professor Fritz Vahrenholt (European Energy Review, May 2, free registration required). Vahrenholt, chief of RWE Innogy, self-proclaimed climate expert and author of the book Die Kalte Sonne (The Cold Sun), claims that “the contribution of CO2 to global warming is being exaggerated”. These claims, however, do not stand up to scientific scrutiny. We assess his ideas in the light of the scientific literature on the role of the sun versus other climate forcing factors. The dominant influence of greenhouse gases follows not only from their basic physical properties, but also from their “fingerprint” in the observed warming. The sun, in contrast, has not exhibited any warming trend over the past 50 years. The sun is thus not responsible for the warming seen during this period. Greenhouse gases in all likelihood are.

Confusing the net cloud effect with a cloud feedback: Very different beasts

I stumbled upon a new post at WUWT today:

New peer reviewed paper: clouds have large negative-feedback cooling effect on Earth’s radiation budget

Note that Anthony has since changed the title to leave out the word “feedback”, which was the source of his confusion. It starts out as follows:

Oh dear, now we have three peer reviewed papers (Lindzen and Choi, Spencer and Braswell, and now Richard P. Allan) based on observations that show a net negative feedback for clouds, and a strong one at that. (…) The key paragraph from the new paper:

…the cloud radiative cooling effect through reflection of short wave radiation is found to dominate over the long wave heating effect, resulting in a net cooling of the climate system of −21 Wm−2.

The attentive reader will immediately spot the problem here. Watts is confusing two issues:

- the net radiative effect of clouds on climate (i.e. in comparison with having no clouds at all)

- the net feedback of clouds in response to a change in climate

The paper addresses the first, whereas Anthony interpreted it as if it addresses the second.

These are two distinctly different issues. The latter (clouds as feedback) is about how cloud cover and properties might change in response to a warming or cooling of the climate: Will the net cloud radiative effect (i.e. the former) become more or less negative.

The net radiative effect of clouds on Earth’ climate has long been known to be negative (i.e. cooling). See e.g this quote from the paper:

The overall global net cloud radiative effect is one of cooling as documented previously (Ramanathan et al., 1989).

That can be verified in any textbook on the subject and most introductions of papers on this topic. Or in my introductory post on aerosols, clouds and climate.

I pointed this error out in the thread, as did more than a few others after me (including Roy Spencer). Only after the author of the paper, Richard Allan, came in to say that this post mis-interpreted the paper, did Anthony change the title and added an update. The mistaken interpretations are still in the body of the text though.

Richard Allan wrote to me in email (reproduced with permission):

I was surprised that this paper was linked to cloud feedback since, as you mention, it attempts to quantify the well known influence of cloud on Earth’s radiation budget (at the top of the atmosphere, at the surface and within the atmosphere and also during day and night) and does not attempt to diagnose cloud feedback.

Watts goes on to say (bold in original):

The cooling effect is found to be -21 Watts per meter squared, more than 17 times the posited warming effect from a doubling of CO2 concentrations which is calculated to be ~ 1.2 Watts per meter squared.

He’s comparing apples and oranges. The 21 W/m2 is the top of the atmosphere (TOA) cloud forcing in reference to having no clouds at all (see table 1 in the paper); the 1.2 W/m2 is the surface forcing due to a doubling in CO2 concentrations. The TOA forcing of a doubling in CO2 is closer to 4 W/m2. But that’s not the “zero” point. The total greenhouse effect (due to water vapor, clouds, CO2 and other GHG) is about 150 W/m2.                                                                                                                   

In other words, this paper falls squarely within the mainstream; it further quantifies a (previously known) net cooling effect of clouds on the Earth’ climate; it does not quantify how clouds may change in response to warmer climate (cloud feedback), though it does provide a carrot stick in saying that these types of analyses are important “in assessing cloud climate feedbacks which contribute substantially to uncertainty in climate prediction.”. That may very well be, but it hasn’t been done in this paper (as confirmed by its author). 

Judging by the comments, many at WUWT took this, in combination with the whopping -21 W/m2, to mean that they discovered a gigantic negative feedback. Nope.

Tallbloke (from Lisbon fame) still insists that

if [cloud forcing] becomes slightly less negative, it’s still very negative, and overwhelms the effect of changes in co2.

… being very confused. Comments vary over a very wide range though. Many are confused (e.g. stating that as specific humidity goes up in a warmer world, so should cloud cover, whereas cloud formation depends on relative humidity rather than on specific humidity), there’s lots of laughing-at-the-scientists going on, but there are also sensible comments that either offer insight or good questions.

Mosher makes the following observation:

it is also fascinating because of what we dont see. usually you will see a whole crew of commeters pounce on the word “model”. This time they didnt.

They didnt because they thought the paper supported spencer. But it was on an entirely different topic. That misunderstanding kinda silenced the usual “models are bad” crew.

Spencer and Braswell fundamentally flawed, journal editor resigns

Wolfgang Wagner, editor-in-chief of the journal Remote Sensing, resigns over the publication of a fundamentally flawed paper:

[peer review is] supposed to be able to identify fundamental methodological errors or false claims. (…) the paper by Spencer and Braswell that was recently published in Remote Sensing is most likely problematic in both aspects and should therefore not have been published.

Peter Gleick has a good rundown of the story.

Wagner points out that minority views are and should be welcomed in the scientific literature. But he adds that that does not mean that long refuted arguments should be able to keep being published:

The problem is that comparable studies published by other authors have already been refuted in open discussions and to some extend also in the literature, a fact which was ignored by Spencer and Braswell in their paper and, unfortunately, not picked up by the reviewers. In other words, the problem I see with the paper by Spencer and Braswell is not that it declared a minority view (which was later unfortunately much exaggerated by the public media) but that it essentially ignored the scientific arguments of its opponents. This latter point was missed in the review process, explaining why I perceive this paper to be fundamentally flawed and therefore wrongly accepted by the journal.

What Stoat reads this to mean is that

Yes, novel and interesting challenges to the established view should be published – perhaps even get given a slightly easier ride, if they are novel. But No: just saying the same old thing again isn’t any good.

Quite predictably, Roy “Conspiracy” Spencer is complaining about the IPCC gatekeepers trying to silence dissenting geniuses like him.

Update: Dan Satterfield observes that

They ["skeptical" papers such as Spencer's] are not published to further the science, but as a piece of meat to those who find the science very incompatible with their world view.

Dutch translation of this post on my NL klimaatblog.

Update 2: Robert Grumbine reminds us of how Spencer sees his own role:

“I view my job a little like a legislator, supported by the taxpayer, to protect the interests of the taxpayer and to minimize the role of government.”

In the comments, Bob Brand makes several astute observations on the course of events and on Wagner’s apology to Trenberth (and the role of cultural differences therein). Re the apology, I see Wagner’s resignation as an apology to the scientific community and don’t find personal apologies to Trenberth necessary, though BB provides some rationale for this.

William Connolley provides some insights:

people are using short-cuts to try to evaluate who is correct. This is inevitable; if we restricted discussion to those who understood the issues, there would be far less debate.

(…) the obvious explanation for Wagner’s explanation, the one he actually gave: personal morality. He doesn’t want to be associated with this paper, and has used the only means available to free himself.

I would sum up Wagner’s reasons for resigning as follows:

• the lack of considering (previously published) contradictory evidence.
• the (in Wagner’s words) problematic issues w.r.t. “fundamental methodological errors or false claims.”
• Spencer’s exaggerations and over-interpretations of his results (which made Wagner feel that he had been taken for a ride).

Scott Denning’s smashing presentation at Heartland climate conference ICCC6

Listen to Scott Denning’s sharp and to-the-point presentation, which he gave at Heartland’s climate conference, here. It’s worth the full 16 minutes of it. He rocks. Alternatively, read this little recap:

Denning attended the Heartland conference for the second year in a row and it seems like he’s outdone himself by giving an even better and sharper presentation than last years (which was excellent as well).

He emphasized some very important things:

- The big picture is what matters; details do not (at least in terms of policy relevance; for science nerds of course it’s different)

- Part of that big picture is that, whatever the sensitivity, a 400% increase in CO2 is going to make a big difference to the climate, because of the simple fact that adding heat warms things up.

- He offered a big challenge to the (strongly contrarian and libertarian) audience: Propose and advocate for effective solutions, otherwise others will. Policy will be enacted anyway. His challenge got particularly strong when he said “do you want Greenpeace to dictate the policy? (…) Are you cowards?”

How science does and does not work (and how skeptics mostly fall in the latter category)

Another kick-ass article on The Conversation, providing some insights into the scientific process and the place that pseudo-skepticism takes in (or rather outside of) that process.

In science, to actually contribute at the forefront of a field one has to earn credibility, not demand it. Being taken seriously is a privilege, not a right.

In science, this privilege is earned by not only following conventional norms of honesty and transparency but by supporting one’s opinions with evidence and reasoned argument in the peer-reviewed literature.

This is what makes science self-correcting. If arguments turn out to be wrong, in time they are caught and corrected by other scientists. It is virtually impossible to publish long-refuted nonsense in good peer-reviewed journals.

(…)

an overwhelming scientific consensus does not imply the absence of contrarian voices even within the scientific community.

Over time, those contrarian voices simply fade away because no one takes them seriously, despite their shouts of “censorship” and accusations of bias.

This is not to say that a scientific consensus is never overturned.

There are well-known examples such as the Helicobacter pylori discovery in medicine, and continental drift in geology. But in both cases the arguments were won and lost in the peer-reviewed literature, not by contrarians sitting on the side-lines writing opinion pieces about how they were being oppressed.

A ‘change in paradigm’ occurs when the evidence for the prevailing theory is shown to be weak, and the evidence for a competing theory is getting stronger. That is the opposite of what has been happening in climate science over the past 150 years: The evidence of human influence on climate has been steadily accumulating from the time that it was first postulated as a prediction. Arguments against it have been shown to be either wrong or irrelevant for the big picture.

Even more so, the prevailing paradigm (that us tiny humans can’t possibly compete with the great forces of nature in affecting the earth’ climate) has been gradually overturned by the evidence which pointed out that yes, we can.

Oreskes gives a good overview of how climate science stacks up against the scientific methods (Highly recommended: “How do we know we’re not wrong?” slides and book chapter).

Back to The Conversation. Read and shudder:

One self-proclaimed “rocket scientist” who has published junk science in the opinion pages of The Australian has been quoted on aNew Zealandwebsite as saying:

“To win the political aspect of the climate debate, we have to lower the western climate establishment’s credibility with the lay person. And this paper [an accompanying picture book of thermometers] shows how you do it. It simply assembles the most easily understood points that show they are not to be entirely trusted, with lots of pictures and a minimum of text and details. It omits lots of relevant facts and is excruciatingly economical with words simply because the lay person has a very short attention span for climate arguments. The strategy of the paper is to undermine the credibility of the establishment climate scientists. That’s all. There is nothing special science-wise.”

Undermine credibility.

That’s all.

Nothing science-wise.

Are these the people one should entrust with the welfare of future generations?

The tried and tested strategy of sowing doubt in the minds of the public seems to be supplemented by a strategy of lowering the scientists’ credibility. The latter strategy seems to be at least as successful as the former, if recent events are any guide.

PS: I’m well aware that the bulk of public skepticism is not based on a well orchestrated campaign, but stems more from individual reasons (which I’ve discussed in a previous post). That does however not negate the fact that certain lines of reasoning are repeatedly used in the public debate.

Another necessary element of denial is conspiratorial thinking. Any denier sooner or later, whether an academic or not, must resort to a global conspiracy theory to negate the overwhelming evidence arrayed against them.

(…)

Just imagine the devastating rebuttal of climate change that Bob Carter could submit for peer-review if he wasn’t being oppressed by the Archbishop of Canterbury and Prince Charles.

(…)

Time to close the phony debate on climate science

At a time when the oceans are accumulating heat at the rate of five Hiroshima bombs per second, are conspiracy theorists the people whom a nation should entrust with the future of our children?

The so-called “debate” on climate change has been over for decades in the peer-reviewed literature. It is time to accept the scientific consensus and move on, and to stop giving air-time to the cranks.

It is time for accountability.

Other articles on The Conversation that I enjoyed reading:

Part Two: The greenhouse effect is real: here’s why.

Part Three: Speaking science to climate policy.

Part Seven: When scientists take to the streets it’s time to listen up.

PS: Even though I chose not to use the word “denier” to describe those who don’t accept mainstream science, I did not change it from the original text as quoted. However, I do not intend to host a discussion here on the arguments pro and con of using this or the other label.

New definition of lukewarmer

This self-description of a lukewarmer (at Bishop Hill) gave me a good laugh:

Now I’m probably some sort of a lukewarmer – I don’t e.g. agree with Turning Tide that the fact that CO2 concentrations are low means ipso facto that it is irrelevant.

Like luketoxers who acknowledge the fact that arsenic in low concentrations doesn’t ipso facto mean that it’s irrelevant. It’s like saying I’m not a total doorknob.

Curious, I went back to read what Turning Tide had written and came across this gem:

What I found most telling is how certain facts about the atmosphere are very hard to track down for the layperson. For example, I’m pretty sure the average joe has no idea how little CO2 there is in the atmosphere, and how small a proportion of that little amount is contributed by human activities. It’s almost as though there’s a conspiracy of silence to keep such information out of easily accessible sources.

Can everyone who has a CO2 concentration widget on their blog please remove it now? We’ve got to keep it a secret that its concentration is a meagre 395 parts per million.

Eric Wolff on areas of agreement and on the public debate about climate science

Dr. Eric Wolff is spot on (see also further below): 

as an outsider to the blogosphere, it surprises me that so many people, presumably mostly with even less knowledge and training than me, seem absolutely convinced they have mastered every area of climate science.

A peculiar line-up of speakers assembled recently at the Conference on the Science and Economics of Climate Change in Cambridge: Phil Jones, Andrew Watson, John Mitchell, Michael Lockwood, Henrik Svensmark, Nils-Axel Morner, Ian Plimer, Vaclav Klaus and Nigel Lawson. Bishop Hill reports that

Dr Eric Wolff of the British Antarctic Survey tried valiantly to find a measure of agreement between the two sides.

This proved an interesting exercise and resulted in a useful list (also reproduced by Judith Curry) on what we can all agree on (perhaps excluding those too far out on the fringes; links added by me):

1. CO2 does absorb infrared radiation
2. The greenhouse effect (however badly named) does occur in practice: our planet and the others with an atmosphere are warmer than they would be because of the presence of water vapour and CO2.
3. The greenhouse effect does not saturate with increasing CO2
4. The CO2 concentration in the atmosphere has risen significantly over the last 200 years
5. This is because of anthropogenic emissions (fossil fuels, cement production, forest clearance). [Ian Plimer disagreed, but as Curry stated: "the anthropogenic contribution is (should be) undisputed"]
6. If we agree all these statements above, we must expect at least some warming. [Bishop Hill noted “broad agreement” with this point]
7. The climate has warmed over the last 50 years, [as is evident from] land atmospheric temperature, marine atmospheric temperature, sea surface temperature, and (from Prof Svensmark) ocean heat content, all with a rising trend.
8. We probably don’t agree on what has caused the warming up to now, but it seemed that Prof Lockwood and Svensmark actually agreed it was not due to solar changes, because although they disagreed on how much of the variability in the climate records is solar, they both showed solar records without a rising trend in the late 20th century. [Excellent point and ironically hitting Svensmark with a stick of his own making. Note the distinction between variability and trend.]
9. On sea level, I said that I had a problem in the context of the day, because this was the first time I had ever been in a room where someone had claimed (as Prof Morner did) that sea level has not been rising in recent decades at all.  I therefore can’t claim we agreed, only that this was a very unusual room.  However, I suggested that we can agree that, IF it warms, sea level will rise, since ice definitely melts on warming, and the density of seawater definitely drops as you warm it.
10. Finally we come to where the real uncertainties between scientists lie, about the strength of the feedbacks on warming induced by CO2 [i.e. climate sensitivity]

Eric Wolff also chimed in with a substantial comment over at Bishop Hill’s, rebutting some commonly heard arguments and making some very spot-on remarks:

(…)

I should first state the rationale for the summary I made at the Downing event. The meeting was about the science and economics of climate change, and I was asked to lead a discussion that came between the science talks and the two economics talks. I therefore felt the most useful thing I could do was to try to summarise what we had heard, as a basis for the discussion of whether society should do anything in response to that, and if so what. In particular I did hear a surprising number of things on which almost everyone in the room could agree, and it seemed worth emphasising that, rather than rehearsing old arguments.

I notice in the thread here several comments about who sets the “terms of the debate”, and about the “context of the debate”. While such phrasings may make sense in discussing energy policy, it is a strange way to discuss the science. Our context is the laws of physics and our observations of the Earth in action; our aim as scientists is to find out how the Earth works: this is not a matter of debate but of evidence. I think some of the comments on this blog come dangerously close to suggesting that we should first decide our energy policy, and then tell the Earth how to behave in response to it.

Regarding Plimer’s proposal that volcanic emissions were more important than we thought, (…) if volcanoes were “causing” the recent increase, then around 1800 their emissions would have had to rise above their stable long-term rate, and then stayed high. This is however a rather hypothetical discussion because the change in the isotopic composition of CO2 in the atmosphere over the industrial period is not consistent with an increased volcanic source anyway.

Regarding the idea that the “temperature increase stopped in 2000”: my point is that we know there are natural variations (due eg to El Nino) that cause runs of a few years of temperature colder than the average or a few years warmer. Look on the record at the decade around 1910 for example when there was a long run of cold years on a flat background.

Such a period superimposed on a trend would look like the last decade (but more so). The point of my analogy is that you can’t determine the trend over several months by measuring the gradient in a run of a few days. Similarly, you simply can’t determine a multidecadal trend by measuring the gradient over a few years because all you get is the “noise” of natural variability.

Professor Morner claims that globally sea level has not risen at all; he dismisses the evidence, from both satellites and the global tide gauge network, that it has. (…) There are numerous reasons why a single site can show a sea level signal, either real or apparent, that departs from the global mean.

I am not the best person to discuss models and feedbacks in detail (see comment on expertise below). However, I could not let two issues pass. Firstly, when models are run out for a century into the future, they do indeed show runs of years with flat temperatures amidst a trend (…) (because of El Nino and other natural factors). I am therefore not clear why this is evidence that something is missing. Regarding positive feedbacks: a positive feedback implies amplification, but not a system out of control; this is only the case if the sum of the gain factors is greater than 1.

Finally, a few specific issues that interested or worried me.

(…) CO2 emits infrared as well as absorbing it. (…) indeed, this property is precisely why its effects do not saturate (but fall logarithmically), because it allows the height from which the emitted radiation finally escapes to rise into regions with less and less air.

Geckko accidentally made an important point. S/he did not like the statement: “We can agree that if it warms the sea level will rise”, because it was too simplistic. Well, as a scientist I always like to boil things down to a statement that my brain can grasp, but that contains the essential explanation of an observation or process. And this one does, for example being demonstrably what was observed in going from a cold ice age world, with sea level 120 metres below the present level, to the present. However, you are right: there are factors that could make this statement false, such as increased snowfall when it warms, adding more ice into ice sheets. As soon as several such competing processes have to be taken into account, our brains cannot predict the outcome, and so we have to resort to putting all the “millions of assumptions” into a numerical model and seeing which of them “win”. An argument for models?

Coldish made a good point about expertise, and this is where I am going to go into a slightly more challenging area. I freely admit that I am not an expert on all, or even most, aspects of climate. When I reach a topic that I have not previously studied, I go to those who are experts, either in person or by reading their work. I maintain scepticism about some of their conclusions, but my working assumption is that they are intelligent and that they have probably thought of most of the issues that I will come up with. Can I observe as an outsider to the blogosphere, that it surprises me that so many people, presumably mostly with even less knowledge and training than me, seem absolutely convinced they have mastered every area of climate science.

and more so, convinced that they are right and almost all of the experts are wrong. That must be the height of hubris.

However, Coldish specifically mentioned IPCC, and I think there is also an interesting point to make about that. At the Downing event, there seemed to be two IPCCs in the room. To some it was a huge plot, masterminded by some mysterious power that manipulates troublesome scientists. To me and the scientists in the room, it is (at least in WG1) simply a set of well-researched review papers, describing the present state of the peer-reviewed literature. I mention this only because I think the former view is a type of groupthink where, because people form an extreme opinion in their private space, they think it is widely held, or even true.

Alas, Wolff’s forray into the blogosphere was short, as is evident from a short comment a while later:

Just in case anyone thinks they are addressing me with their remarks:

I thought this might indeed be a chance for a civilised discussion, and some of the respondents seem happy to have that. However there are also a lot of remarks on here that are frankly rude and aggressive, and I won’t be returning. Now I remember why I hate the blogosphere.

Different approaches to the climate problem

The approach people take to climate change varies widely. They can be distinguished e.g. by the importance they place on climate change (or trust placed in the science), and by the conditions they put on potential solutions or response strategies. This gives rise to four different response strategies to the problem, along two axes:

Some archetypical responses for each quadrant are laid out in this cartoon:

⁽*⁾: To which the German Coastguard in need of English language training replies: “What are you sinking about?” Cartoon adapted from Jip Lenstra.

There are of course loads of varieties possible here. Some contrarians may say: The water looks pretty nice. Some scientists (and so called “merchants of doubt”) are in fact saying: We’re thinking (and are not sure what’s happening. Let’s wait and see). Libertarians may say that life boats commissioned by the government are not to be trusted. And some greens may dream up a world of mermaids.

There are some interesting dynamics between the different archetypes: Most arguments happen in the horizontal direction (belief vs disbelief in an impending climate catastrophe; trust vs distrust of climate science; liking vs disliking certain lifeboats), whereas most liaisons occur in the vertical (between people who share the same (dis-)belief in climate change, but differ in the restrictions they place on response strategies).

Arguments on the science occur between the two upper panels: Is the boat sinking? Arguments on the response strategy often occur in the realm of the lower two panels: What restrictions (if any) do we place on the lifeboats? Are other agenda’s playing a role (besides wanting to save our souls)? Sometimes, the lower two panels actually partner up, like in those cases where they share a dislike for a certain lifeboat (CCS for example). Naturally, if you’re on a sinking boat most people will let go of any restrictions. Perhaps we can turn that around: The more restrictions people place on the lifeboat, the less severe they apparently think the problem is (in comparison with other issues).

If you think the boat can’t sink (upper left), then it doesn’t make sense to invest in a life-boat (lower left). Unless you like the lifeboat for another reason, e.g. for energy independence or to avoid peak oil. That would be a typical lower left panel response: You want a specific boat, but you don’t care much about climate change. Burning coal is perfectly fine according to this mindset. If OTOH you think the boat is sinking (upper right), then it makes sense to get a life boat (lower right).

The reverse is also happening (much to the detriment of the discussion): Some people have such a strong dislike for the lifeboat (lower left), that they therefore deny that the boat is sinking (upper left). Others like green lifeboats so much (lower right), that they shout out loud that the boat is sinking (upper right) without actually understanding how or why or when. They are prone to exaggerating the problem.

These styles of argument (from bottom to top) basically argue the science as a proxy for what the disagreement is really about: Liking or disliking certain boats.

Gotta love analogies…

Radiative forcing by aerosol used as a wild card: NIPCC vs Lindzen

(This is also featured as a guest post on Skeptical Science)

The greatest source of uncertainty in understanding climate change is arguably due to the role of aerosols and clouds. This uncertainty offers fertile ground for contrarians to imply that future global warming will be much less than commonly thought. However, some (e.g. Lindzen) do so by claiming that aerosol forcing is overestimated, while others (e.g. the NIPCC) by claiming that aerosol forcing is underestimated. Even so, they still arrive at the same conclusion…

Let’s have a look at their respective arguments. Below is a figure showing the radiative forcing from greenhouse gases and from aerosols, as compared to pre-industrial times. The solid red curve gives the net forcing from these two factors. The wide range of possible values is primarily due to the uncertainty in aerosol forcing (blue dotted line).

The greenhouse gas forcing (dashed red curve) is relatively well known, but the aerosol forcing (dashed blue curve) is not. The resulting net anthropogenic forcing (red solid curve) is not well constrained. The height of the curve gives the relative probability of the associated value, i.e. the net climate forcing is probably between 1 and 2 W/m², but could be anywhere between 0 and 3 W/m². (From IPCC, 2007, Fig 2.20)

NIPCC’s argument

The NIPCC report (a skeptical document, edited by Craig Idso and Fred Singer, made to resemble the IPCC report) says:

“The IPCC dramatically underestimates the total cooling effect of aerosols.”

They hypothesize that natural emissions of aerosol precursors will increase in a warming climate, causing a negative feedback so as to dampen the warming. Examples of such gaseous aerosol precursors are dimethyl sulfide (DMS) emitted by plankton or iodocompounds created by marine algae. They use these putative negative feedbacks to claim that

“model-derived sensitivity is too large and feedbacks in the climate system reduce it to values that are an order of magnitude smaller.”

Rebuttal

These are intriguing processes (the “CLAW hypothesis” first got me interested in aerosols, when I assisted with DMS measurements on some remote Scottish islands), but their significance on a global scale is ambiguous and highly uncertain. As a review article about the DMS-climate link says:

“Determining the strength and even the direction, positive or negative, of the feedbacks in the CLAW hypothesis has proved one of the most challenging aspects of research into the role of the sulfur cycle on climate modification.”

The NIPCC report exaggerates the uncertainty in climate science, but seems to put a lot of faith in elusive and hardly quantified processes such as natural aerosol feedbacks coming to our rescue.

Lindzen’s argument

On to Lindzen:

“The greenhouse forcing from man made greenhouse gases is already about 86% of what one expects from a doubling of CO2 (…) which implies that we should already have seen much more warming than we have seen thus far (…).”

Lindzen again (E&E 2007):

“How then, can it be claimed that models are replicating the observed warming? Two matters are invoked.”

The “two matters” he refers to are aerosol cooling and thermal inertia from the oceans (a.k.a. “warming in the pipeline”). He then proceeds to argue that both of these factors are much smaller than generally thought, perhaps even zero. E.g. on aerosols, Lindzen writes:

“a recent paper by Ramanathan et al (2007) suggests that the warming effect of aerosols may dominate – implying that the sign of the aerosol effect is in question.”

By downplaying the importance of these two factors, Lindzen argues that the observed warming implies a small climate sensitivity. The same line of argument is also used by Dutch journalist Marcel Crok, who writes in his recent book (in Dutch, my translation):

aerosols probably cool much less than commonly thought

Rebuttal

While it is true that aerosols can warm and cool the climate (by absorption and reflection of solar radiation, respectively, besides influencing cloud properties), most evidence suggests that globally, cooling is dominant. Whereas Ramanthan et al (2007) don’t quantify the net aerosol effect (in contrast to Lindzen’s implicit claim), Ramanathan and Carmichael (2008) (quoted by Crok) do. They estimate both the warming ánd cooling effects to be stronger than most other estimates, but the net forcing (-1.4 W/m²) is right in line with (even a little stronger than) the IPCC estimate (see the above figure). Taking into account realistic estimates of aerosol forcing and ocean thermal inertia, the earth has warmed as much as expected, within the admittedly rather large uncertainties. Ironically, it is exactly because aerosol forcing is so uncertain and because the climate hasn’t equilibrated yet that the observed warming since pre-industrial times is only a very weak constraint on climate sensitivity. Lindzen seems very certain of something that most scientists would readily admit is very uncertain.

Conclusion

So we have the peculiar situation that both of these approaches try to claim that climate sensitivity is small, but the NIPCC approach is to claim that aerosol forcing is very large (thus providing a negative feedback to warming), whereas the Lindzen approach is to claim that aerosol forcing is very small (thus necessitating a small sensitivity to explain the observed warming so far). Of course they can’t both be right, and probably neither of them are. Looking back at the figure above, both approaches are based on assuming that aerosol forcing is at the edge of the probability spectrum (as if it were some fudge factor), whereas the most likely value is somewhere in the mid range. Both approaches also ignore the other lines of evidence that point to climate sensitivity likely being in the range of 2 to 4.5 degrees. E.g. a value as small as suggested by the NIPCC (0.3 degrees) is entirely inconsistent with the paleo-climate record of substantial climate changes in the earth’ history. And finally, both approaches implicitly assign high confidence to some of the most uncertain aspects of climate science, even though they routinely mock climate science as if nothing is known at all.

Of course it is not mandatory for all those who dismiss mainstream climate science to agree, but to see two important “spokespeople” for climate contrarians take such mutually inconsistent approaches is peculiar. Even more so when you realize that Lindzen signed the recent “prudent path” letter to US Congress, in which the NIPCC report was approvingly cited… Most people can’t have it both ways, but apparently climate contrarians can.

See also a more detailed critique of the NIPCC and of Lindzen’s argument.

Arctic sea ice was higher in 1989 cherrypicking by Harrison Schmitt and Heartland Institute

How could someone possibly claim that

Arctic sea ice has returned to 1989 levels of coverage

Easy. The proof is in the data, of course:

See: The red line is clearly higher than the blue one in april. 

Is this a joke? I wish. This was said by ex-astronaut and New Mexico’s energy secretary Harrison Schmitt. The Heartland Institute had carefully picked april of 1989 and 2009 as the basis for comparison.

As regular readers here know, I’m very open to different opinions and to reconciliation efforts. But this has of course nothing to do with true skepticism. Look at those two lines! This is definitely not the kind of “skepticism” that we should be taking more seriously. I hope everybody (including Judith Curry) can at least agree to that. I’m all for bridge building, but let’s at least make sure that reality remains somewhat in view while standing on the bridge.

See also Scott Mandia, Chris Mooney, Charlie Petit, Lou Grinzo, Richard Littlemore, Tim Lambert (suitable title: “Now THAT’s cherrypicking”), Peter Sinclair and Peter Gleick at the HuffPo.

Graph via Tim Lambert and Peter Gleick. Pictur here.