An Interview with Top Climate Scientist Bjorn Stevens

From Dr. Judith Curry’s Climate Etc.

by Nic Lewis

This week Die Zeit published an interview with Bjorn Stevens. Die Zeit is the largest German weekly newspaper (circulation well over one million), and has a highly educated readership.  

Bjorn Stevens is Director at the Max Planck Institute for Meteorology, the principal German climate science research and modeling centre. He is very well known for his work on climate sensitivity, aerosols and, particularly, clouds. Professor Stevens is an excellent scientist and a key figure in the climate science establishment. He is joint lead co-ordinator of the World Climate Research Programme’s Grand Challenge on Clouds, Circulation and Climate Sensitivity, and led the 2015 Ringberg Castle workshop that kicked off its climate sensitivity arm.

The interviewer, Max Rauner, an experienced science journalist with a PhD in physics, focused mainly on clouds, however Stevens also had interesting things to say about pronouncements by alarmist climate scientists. An English translation of the interview appears below.Read more


Climate research: “Too many children’s book clouds”

How much fear are scientists allowed to spread in the climate debate? Cloud researcher Bjorn Stevens accuses his colleagues of being alarmist. He finds: We still know far too little.

What do the clouds do when the climate warms up? This is what Bjorn Stevens, director at the Max Planck Institute for Meteorology in Hamburg, is researching. His research group simulates clouds in climate models. When it comes to cloud issues, the World Climate Report relies heavily on his expertise. At the moment, however, Stevens would like to rewrite the world climate report.

DIE ZEIT: Professor Stevens, the world climate report describes clouds as the greatest uncertainty factor for climate forecasts. Why is that?

Bjorn Stevens: See that cloud out there? In my field, most people think of a cloud as these compact white objects in the blue sky.

ZEIT: Just like in the children’s book.

Stevens: Yes, a pretty fluffy cloud. As if you could draw a line around the edge of the cloud. But that’s an optical illusion, as anyone who’s climbed into a cloud in the mountains knows.

ZEIT: Because it’s getting foggy?

Stevens: Exactly. Clouds are tricksters. Even if the contours are sharp, the cloud structure is more like that of puff pastry. Nevertheless, many scientists use the children’s book clouds as a guide because they are easier to simulate. This makes the climate models less accurate.

ZEIT: How much water does this cloud contain?

Stevens: A cloud the size of an old building can only hold a liter of water.

ZEIT: That would fit in a pint of beer!

Stevens: If you distributed all the condensed water in the atmosphere evenly around the globe, you would get a water film that is only two tenths of a millimeter thick.

ZEIT: Why then do clouds affect the climate so much and flood entire countries?

Stevens: Flooding occurs because clouds can be huge and air circulation during storms constantly replenishes the water. And they affect the climate because they are made up of a huge number of droplets that interact with sunlight and thermal radiation. A very large cloud has almost as many droplets as there are stars in the universe. And there are many clouds.

ZEIT: Are they warming or cooling the planet?

Stevens: Both. The energy balance of the earth has two parts: firstly, the incident sunlight and secondly, the heat given off by the earth, i.e. infrared radiation. All clouds have a cooling effect by reducing the amount of sunlight that reaches the earth’s surface. And all clouds have a warming effect by absorbing the earth’s infrared radiation so it doesn’t escape into space – the greenhouse effect. The balance sheet shows: Water-rich low clouds over the tropical ocean have the greatest cooling effect and low-water ice clouds at high altitudes have the strongest warming effect. Overall, the cooling effect is greater.

ZEIT: And how does this balance change with global warming? Scientists from the Potsdam Institute for Climate Impact Research (PIK) recently published a worst-case scenario . It also mentions that by the end of the century our planet could get so warm that all the clouds are practically evaporating and we are doomed.

Stevens: That’s nonsense. Put simply, the atmosphere wants to be cloudy because air rises. It’s hard to get rid of clouds.

ZEIT: Why do the Potsdam climate researchers claim otherwise?

Stevens: You’ll have to ask them that. I can only admire how the colleagues there comb through the specialist literature for the most alarming stories. I find it a pity that these are then presented uncritically.

ZEIT: So the scenario is wrong?

Stevens: Yes. It is based on a work by our institute taken out of context and on a second paper that has numerous shortcomings.

ZEIT: What shortcomings?

Stevens: The dramatic behavior of the climate in this simulation was based on an oversimplification of the clouds, which has nothing to do with reality. If you look closely, the most alarming stories often don’t stand up to scientific scrutiny.

ZEIT: Do you also mean tipping point forecasts such as the melting of the Antarctic ice sheet, the collapse of the Gulf Stream and the desertification of the Amazon rainforest?

Stevens: Yes, and most others. Of course, the world will change as a result of global warming, even more dramatically in some regions. But how, where and when is far from certain.

ZEIT: In the German climate discourse, the PIK usually warns of tipping points , while your institute tends to downplay the danger of tipping points. Why is that?

Stevens: Tipping points are fascinating, and there’s a good chance they exist. But they are also a matter of definition. What do you think of when you hear the word tipping point?

ZEIT: Of a self-reinforcing feedback that is irreversible.

Stevens: An accelerating change that cannot be reversed, right. Like a pencil falling down. He cannot fall back up by himself. But the tipping points highlighted by my colleague Hans Joachim Schellnhuber and others at PIK are based on their private, much weaker definition . Tipping points are reinterpreted to include less abrupt or even reversible climate changes. With this redefinition, they find tipping points everywhere. Then the alarm goes off. My institute does not play down tipping points, we just place more value on clarity.

ZEIT: Do you envy the Potsdam Institute for its media presence ?

Stevens: Who doesn’t want to be interesting? Unfortunately, people prefer stories about the end of the world. I don’t understand much about that.

ZEIT: Are you saying that global warming is not a problem?

Stevens: It’s a huge problem, partly because we know so little about its actual impact. According to the IPCC , whether and where biblical droughts and floods will occur is uncertain for almost all regions .

ZEIT: Stefan Rahmstorf from PIK compares himself to a doctor who found out that smoking is dangerous and now has to call on people to stop.

Stevens: As a scientist, I like to explain to people how things I understand work. But what qualifies me to tell them how to behave? That must result from the social discourse, which should be shaped more by good journalism than by charismatic scientists. If people don’t learn to think for themselves, we’re lost anyway.

“The contribution of the clouds is still overrated”

ZEIT: Let’s talk about the danger of clouds again. Will Clouds Accelerate Global Warming?

Stevens: The interesting number here is climate sensitivity. It quantifies how much the earth will warm up if the CO₂ concentration in the atmosphere doubles…

ZEIT: …compared to the CO₂ concentration before industrialization. That would still be in this century?

Stevens: If we continue as before, yes. In the last IPCC report , it was agreed that the global average temperature would then probably rise by 2.5 to 4.0 degrees Celsius. According to the simulations, the higher temperatures are mainly caused by a change in the clouds. We consider this effect to be overestimated today.

ZEIT: Were the models faulty?

Stevens: Yes. Too many children’s book clouds, not enough real clouds. In the world climate research program we have tackled the climate models. The models with the most extreme predictions have failed, and confidence in the less catastrophic values of climate sensitivity has increased . In my opinion, however, the contribution of the clouds is still overstated.

ZEIT: How great is it?

Stevens: Based on our latest measurements and advances in theory, I would say today: zero.

ZEIT: Zero?

Stevens: Right, at least that’s my working hypothesis. The climate sensitivity is then at the lower end of the IPCC estimate, around 2.8 degrees. We should keep looking, but so far there’s no evidence that clouds play a major role.


The original German version of the above interview, updated October 19, 2022 at 4:50 pm, is available here.

As a matter of interest, if, in the light of Bjorn Stevens’ comments, one were to replace the cloud feedback estimate given in the recent IPCC Sixth Assessment Report (AR6) with a zero estimate, the AR6 feedback-based estimate of climate sensitivity would reduce by 27%. Applied to the AR6 3.0°C central estimate of climate sensitivity, that reduction would change it to 2.2°C, identical to the feedback-based estimate in my recent paper that estimated climate sensitivity using multiple lines of evidence.


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October 23, 2022 6:15 pm

I’m a bit unclear on this. Does Stevens mean to say clouds don’t have a role in CO2 ECS feedback concepts? or that clouds do not have any role in the climate system energy balance whatsoever? I’m guessing he means the former, since ECS is what climatology has been reduced to. Is there not a hypothesis that CO2 leads to less cloud albedo, resulting in a net SW forcing in response to rising GHGs? It’s all getting a bit confusing to be honest.

Reply to  JCM
October 23, 2022 6:36 pm

Bjorn Stevens is not talking about the total contribution of clouds, he is indeed talking about cloud feedback. See my October 23, 2022 6:34 pm comment here, or my comment in Judith Curry’s blog.

Reply to  Mike Jonas
October 23, 2022 6:46 pm


Reply to  JCM
October 23, 2022 6:59 pm

pardon my lingo, i mean to say a net positive SW ‘effect’ in response to rising GHGs. Personally I think the whole thing is getting tied in knots. Might be best to start from a blank slate. Soon there won’t be much room to incorporate CO2 as the basis of all change.

October 23, 2022 6:34 pm

WUWT Home Page says of this article: “We should keep looking, but so far there’s no evidence that clouds play a major role.“. That’s very misleading. Bjorn Stevens is not talking about the total contribution of clouds, he is talking about cloud feedback. (See my comment in Judith Curry’s blog).

Reply to  Mike Jonas
October 24, 2022 3:33 am

Indeed. The alarmists need a simple story they can use to alarm the public. Even they should be aware that such a strategy pretty much guarantees that they will be wrong.

As far as I can tell, the quote you quote is actually a quote. What makes it misleading is that it is, like any other such quote, lacking in context. I’m also guessing that it’s a translation.

The article itself is highly interesting. It is published in a major publication. Given the current energy problems, I think there’s huge interest in finding a way to back away from the green madness. IMHO, the compromise position is that of Bjorn Lomborg. ie. adaptation to any warming that may actually happen.

October 23, 2022 6:34 pm

Unfortunately, people prefer stories about the end of the world. I don’t understand much about that.

New Yorkers can’t escape the dooming by moving to Florida or Texas as the stories will follow you-
NYU’s ‘Dr. Doom’ says New Yorkers who moved to Florida, Texas, says states won’t ‘survive’ climate change (
That’s the bit you need to understand.

Steve Case
October 23, 2022 7:18 pm

 All clouds have a cooling effect by reducing the amount of sunlight that reaches the earth’s surface.

At night?

Reply to  Steve Case
October 23, 2022 8:00 pm

Sure. Ever heard of the moon? Reflected sunlight.

Reply to  Myron
October 23, 2022 8:26 pm

So why are clear sky nights generally colder than cloudy nights? 🙂

Reply to  StuM
October 24, 2022 9:44 am

The SB radiative transfer formula for 2 flat parallel surfaces with emissivity of .95 is
Q per M^2 = .95 x 5.67e-08 x (Tground ^4 – T sky^4)
Now you can calculate that at Tground of 15C=288K there will be a lot more heat leaving the ground if Tsky is clear outer space at 3K versus cloud bases at OC = 273 K. That’s why clear nights cool quicker than cloudy nights….
Ok, have at me convective pedants ;-)…

Jim Gorman
Reply to  DMacKenzie
October 24, 2022 10:27 am

Ok. Clear sky basically does not reflect energy, therefore the cooling gradient is at it’s maximum.

Clouds “reflect” some amount of the surface radiation energy. This slows the cooling, but doesn’t reverse it. So, let’s say after 1 hour under clear sky the temp would have dropped 10 degrees. With clouds the drop may only be 5 degrees. Is that warmer or cooler?

You must also separate out CO2 vs water, and water separated into liquid/vapor. Can an ice crystal be moved to vapor by a collision with N2/O2? Is heat “lost” when that vapor precipitates again and radiates IR.

It all gets real mixed up.

Eamon Butler
Reply to  Jim Gorman
October 24, 2022 4:32 pm

Yes. Cooling slower may be ”warmer” but it is not ”warming”

Pat from kerbob
Reply to  Myron
October 24, 2022 10:54 am


Reply to  Steve Case
October 23, 2022 8:40 pm

Clouds generally cool by day (shading the surface from sunlight) and warm by night (acting like a blanket holding in outgoing radiation). The overall global effect is a net cooling. The cooling is greatest at the tropics, while clouds in the polar regions (which get much less sunlight) are net warming.

Reply to  Mike Jonas
October 25, 2022 8:56 am

Here in Montana, I regularly see chemtrails that last many hours. Are they trying to cool or warm the atmosphere?

Reply to  Steve Case
October 24, 2022 6:45 am

There are 8 combinations when considering 1) change 2) elevation and 3) timing. The microphysical composition of the clouds effects the magnitude of the radiative forcing as well, but that is a topic for another time.

decrease-high-night = cooling
decrease-high-day = cooling
decrease-low-night = cooling
decrease-low-day = warming
increase-high-night = warming
increase-high-day = warming
increase-low-night = warming
increase-low-day = cooling

Reply to  Steve Case
October 24, 2022 8:56 am

So let’s do some lunchbag calcs…”a kg. of water can make a cloud as big as a house”….so lets say 100 m^2 of ground area….that can easily reflect 400 watts per M^2 so 400×100/1000=40 Kw-hrs of incoming sunlight in an hour…..Meanwhile in a sunny spot between clouds it only takes 0.685 KW of energy to evaporate a Kg of water. So in .685/40 of an hour, about 1 minute, sunlight can generate enough water vapor to generate another 100M^2 of cloud….so it might take a while for that water vapor to waft upwards a thousand meters or so to form a cloud…..but nevertheless the proclivity of any water wet surface to cause clouds which then block the incoming sunlight is very strong. Anyone who believes clouds are overall a positive feedback is fantasizing.

As Lewis Carroll wrote:
“Alice laughed. ‘There’s no use trying,’ she said. ‘One can’t believe impossible things.’I daresay you haven’t had much practice,’ said the Queen. ‘When I was your age, I always did it for half-an-hour a day. Why, sometimes I’ve believed as many as six impossible things before breakfast.”

Reply to  DMacKenzie
October 24, 2022 9:17 am

3rd line, I meant .685 Kw-hrs to evaporate a kg. of water. Forgive me, Dr Walker, my long departed heat transfer prof, for my units transgression….

Last edited 3 months ago by DMacKenzie
Reply to  DMacKenzie
October 24, 2022 9:49 am

Increasing low clouds by day cause cooling. The other 3 combinations of increasing clouds cause warming. The question is what is the net effect of all of the changes.

Last edited 3 months ago by bdgwx
Reply to  bdgwx
October 24, 2022 10:51 am

Very approximately, clouds have a local albedo of .3 to.9 depending on optical depth. let’s call it 0.4….therefore they reflect about 400 watts/M^2 of sunlight back into space (obviously when the sun is shining on them). At night, with say cloud bottom temp of freezing and ground temp of 15 C, there is only about 74 watts/M^2 of net heat radiatively being sent from the ground upwards.
About 65% cloud cover over the planet is generated by the excess daytime heat generating water vapor on the planet’s wetted surfaces, with clouds moved about relatively randomly by “weather”. And the warmer a local surface gets, the more water vapor is generated, in turn generating higher-optical-depth-low-altitude-cumulus clouds…

Geoff Sherrington
October 23, 2022 8:24 pm

“What do the clouds do when the climate warms up?”
They can cause more rain.
Here is a sad outcome from more rain. A newish solar farm, cost $50 million, turned off because it rained. Sunshine Coast holiday region, north of Brisbane, Queensland.
Question, who is accountable for this elementary dersign error?
Who is getting pay docked for being incompetent?
Geoff S

Reply to  Geoff Sherrington
October 23, 2022 10:21 pm

I wonder if it was insured for flood damage? And I wonder how it will recover after the panels dry out.

I did not see anything in the Finkel report on loss of solar output due to panels being underwater. Just one of the many things omitted in that blue sky report.

Reply to  Geoff Sherrington
October 24, 2022 4:39 am

Whoopsie, someone believed in permanent drought.

Reply to  Geoff Sherrington
October 24, 2022 5:48 am

Yes, besides the docked pay for incompetence what about firing the career bureaucrats who authorized it or dock their retirement accounts… There doesn’t seem to be any recourse for these types of incredibly stupid errors which become apparent years in the future.
And it looks like it will become more commonplace as the money is piled on top of the ignorance.

Chris Hanley
October 23, 2022 8:38 pm

Stefan Rahmstorf from PIK compares himself to a doctor who found out that smoking is dangerous and now has to call on people to stop.

From the link:
Prof Rahmstorf: “We are obliged to explain them to the public as well. Just like doctors: if they have recognized that smoking is harmful, they naturally have a duty to communicate this to the general public”.
That often used analogy is totally fraudulent, before cigarette smoking became common lung cancer was a very rare disease, the correlation is stark:
There is no corresponding obvious and direct relationship between atmospheric CO2 concentration changes and changes in the global average temperature at many time scales from millions of years to centuries.
That is not to say changes in CO2 have no effect.

Last edited 3 months ago by Chris Hanley
Robert B
Reply to  Chris Hanley
October 24, 2022 1:04 am

In 1853, J. Adams, a surgeon at The London Hospital, described the first case of prostate cancer, which he discovered by histological examination1. Adams noted in his report that this condition was “a very rare disease”. Remarkably, 150 years later, prostate cancer has become a significant health problem. In the United States, it is the most commonly diagnosed cancer in men, with 180,000 new cases and about 31,000 deaths occurring annually2. This dramatic increase in the number of prostate cancer cases can be attributed to several causes. First, prostate cancer was not differentiated from other types of urinary obstruction until the early 1900s. Second, the incidence of prostate cancer increases more rapidly with age than any other cancer type”

Most lung cancers show up about 70. I don’t know what is meant by age adjusted but your plot looks like data for the US. “In 1930, the lung cancer death rate for men was 4.9 per 100,000; in 1990, the rate had increased to 75.6 per 100,000.” So it appears that there seems little age adjustment to account for doubling of people over 65 since 1950. There is also a diagnosis issue early in the 20th C. Consumption was mostly TB and it would have been unlikely that a doctor would have identified lung cancer as the cause.

Disclosure: I don’t have any interest in promoting smoking. I’m happy to accept that smoking so much burnt material would increase your chances of getting lung cancer. It’s just that is the sort of graph Michael Mann would come up with.

October 23, 2022 8:41 pm

,,,interviewer, Max Rauner, an experienced science journalist with a PhD in physics…

Stevens: A cloud the size of an old building can only hold a liter of water.

ZEIT: That would fit in a pint of beer!

According to a science journalist with a PhD in physics, a liter of water would fit into a pint of beer. Should we be worried about this?

Remind me, just why did we give up on the Imperial measurement system again?

Reply to  dk_
October 23, 2022 9:07 pm

Beat me to it, dk_. That one just jumps out at you.

These are our Intellectual Superiors™?

Reply to  dk_
October 23, 2022 9:57 pm

It could all be in the translation. One of the larger German Steins (mugs) of beer can hold over a litre (liter). Maybe that got translated to “pint”?

Mr David Guy-Johnson
Reply to  dk_
October 23, 2022 11:24 pm

Get real. It’s likely a translation error and not proof of your doubtful intellectual superiority In Germany, Austria , France and much of mainland Europe they have larger measures of beer that aren’t far short of litre

Last edited 3 months ago by Mr David Guy-Johnson
Reply to  dk_
October 23, 2022 11:39 pm

Congratulations for this fundamental conclusion about the content af the interview! In real in the Geman original text they talk about “1 Maß” Beer, this is in Bavaria 1l. Lost in translation…

October 23, 2022 8:47 pm

Stevens claims to be a scientist but comes across in this interview as a simpleton speaking to an audience of teenagers.

Stevens appears to say cloudiness does not change as the troposphere warms and holds more water vapor. If that was true, the water vapor positive feedback from a warming troposphere would eventually cause runaway global warming. That has never happened. One good explanation why runaway global warming has never happened would be that increased water vapor in the troposphere leads to increased cloudiness. There may be anothr explanation, but Stevens does not provide one.

Steven appears to claim the primary reason for high ECS numbers in many climate models is: “According to the simulations, the higher temperatures are mainly caused by a change in the clouds.”
Is that correct? I believe the high computer game ECS numbers are mainly from a HUGE imagined water vapor positive feedback, NOT from changes in cloudiness.

This interview is close to being data-free but science requires lots of data. The only data presented are the IPCC ECS range, and the authors claim of his own ECS, which is within the IPCC range, so the author is confirming the IPCC range. THIS INTERVIEW IS MUCH ADO ABOUT NOTHING

Reply to  Richard Greene
October 23, 2022 9:59 pm

Again, I think there is confusion over what Stevens was actually talking about – cloud feedback not the total effect of clouds.

Reply to  Richard Greene
October 24, 2022 3:43 am

Try reading what you are commenting on next time.

Reply to  lgl
October 24, 2022 6:18 am

I read it two times and find out has the same value as your nasty comment: None

Jimmy h
Reply to  Richard Greene
October 25, 2022 11:51 pm

I am confused also. He claims a total negative but they says zero. For clouds and water vapor in models it is a positive value but evidence suggests it should be negative.

A simple change in values to negative makes climate models align with or at least be close to empirical data.

I know this guy was talking about just clouds, but he seems to contradict himself.

October 23, 2022 10:11 pm

So, clouds have no effect on Equilibrium Climate Sensitivity which means no change in the greenhouse effect but he also says that they contribute to the greenhouse effect.
Then he says that overall, clouds have a net cooling effect which means more clouds gives more cooling.
No mention of more clouds reducing the total amount of incoming solar energy that enters the climate system in the first place by increasing global albedo.
Is this the general standard of science these days?

Reply to  Stephen Wilde
October 24, 2022 5:24 am

I think that a lot has been lost in translation, and also that the statements were made for a very non-scientific general public. The assertion that clouds have no effect on Equilibrium Climate Sensitivity is simply stating that the IPCC and modellers are wrong with their positive cloud feedback – Bjorn Stevens is saying there is zero feedback (NB I think the data shows negative feedback, see my other comments). When he says clouds have a net cooling effect, he is talking about global cloud cover and not about cloud feedback, and the statement is valid. Reflection of sunlight is a large part of the mechanisms for that, and the statement is valid even if he doesn’t mention the mechanisms.

Like I said, a lot is lost in translation, and things could be much clearer in the original German to a German speaker (my German is definitely not up to reading the original German).

Reply to  Mike Jonas
October 24, 2022 6:19 am

Suggested new WUWT policy:
No translated articles here.

Richard Page
Reply to  Richard Greene
October 24, 2022 10:13 am

“Traduttore, traditore”.

Reply to  Mike Jonas
October 24, 2022 8:17 am

“Are they warming or cooling the planet?

All clouds have a cooling effect… Overall, the cooling effect is greater”

“Will Clouds Accelerate Global Warming?”

and after a few follow up questions:
“…the contribution of the clouds is still overstated… Based on our latest measurements and advances in theory, I would say today: zero.”

Nothing unclear and nothing lost in translation.

Reply to  Stephen Wilde
October 24, 2022 8:34 am

All of your writing here is wrong.

CERES measurements show SW to the surface has increased but LW (the GHE of clouds) has decreased by roughly the same amount, so net zero change, just like Stevens says.

No, more high clouds gives warming. More low clouds gives cooling. And position and time of year also matters.

The more than 20 years of CERES data show decreasing albedo.

But yes, sadly this is the general standard of your knowledge of science.

Reply to  lgl
October 24, 2022 11:25 am

Loeb showed planetary albedo and cloud cover change in lockstep. Also its a matter of semantics whether 20 thousandths of a percent peak to peak variation is a “decreasing albedo” or “unchanging albedo”

Last edited 3 months ago by DMacKenzie
Reply to  DMacKenzie
October 25, 2022 12:01 am

Ask them what it looks like with the full CERES period.

October 23, 2022 10:14 pm

Stevens: If you distributed all the condensed water in the atmosphere evenly around the globe, you would get a water film that is only two tenths of a millimeter thick.

The more important component of the water in the atmosphere is the solidified portion. That is the highly reflective component for short wave as well as high absorption of OLR.

Hari Seldon
October 23, 2022 10:22 pm

In the light of the special circumstances in Germany the interview and its publication would be very interesting: The publication in the journal “Die Zeit” signalise very clearly a sharp change in the official German public policy on climate issues. In Germany journals like “Die Zeit” should align with the official policy and earlier was “Die Zeit” an active supporter of the climate and CO2-hysteria. So the U-turn is very clearly detectable. Additionally is Mr. Bjorn Stevens a leading person at the largest German research institution (Max Planck Institute) financed practically 100% by the government/state. Let me allow the conjecture, that it is definitely not by coincidence that such an interview with Mr. Stevens could be published in Germany. Especially his statements regarding the “results” from PIK (Potsdamer Insititute for Climate Impact Research) are “interesting”: To date the position of PIK was the official line of the German public policy on climate issues. The bottom line from the interview published in the journal “Die Zeit”: Some changes in the German public policy regarding climate and CO2 issues have been ongoing.

Reply to  Hari Seldon
October 24, 2022 12:32 am

Indeed, this is not less than a revolution of the minds in Germany… Maybe they have seen the results of their “green” policy, now that the whole German industry is suffering from the extreme energy prices?

Julian Flood
Reply to  Hari Seldon
October 24, 2022 12:45 am

Well, if you are increasing your consumption of open-cast lignite then you need a new excuse. Here it is – AGW is not as big a problem after all. As Germany leads the EU will follow. Perhaps.

Any step away from the hysteria is to be welcomed.


Dave Andrews
Reply to  Julian Flood
October 24, 2022 8:41 am

Germany has the 6th largest coal reserves in the world. Why not burn some of it rather than relying on Russian gas?

They also have a lot of unreliable wind farms that are coming to the end of their normal life in 2025.Meanwhile, the ruinables industry in Germany has lost 50,000 jobs in the last 6 years.

Reality bites back!

Pat Frank
October 23, 2022 10:27 pm

estimated climate sensitivity using multiple lines of evidence.

Statistics is no substitute for physics. I’m so sick of people using statistics to purport physical meaning.

Proxy air temperature reconstructions: Statistics. Unless it’s the scream of a tortured principal component.

Climate models: parameterized engineering narratives extrapolated off into fantasy land, where the statistics of physically meaningless expectation values are represented as accuracy statements.

Global air temperature record, where instrumental resolution is ignored and statistics is abused to zoom all the measurement error into zero.

Climate sensitivity is a fiction unless a valid physical theory of climate allows one to deduce a physically observable impact on sensible heat from CO2 emissions.

There is no such theory. Just to say: radiation physics is not a theory of climate.

Science could not be more betrayed. Nor ethics. It’s sickening.

Reply to  Pat Frank
October 24, 2022 12:23 am

”There is no such theory. Just to say: radiation physics is not a theory of climate.

Science could not be more betrayed. Nor ethics. It’s sickening.”

Why are not more scientists speaking up about this????????????

Reply to  Mike
October 24, 2022 3:40 am

They need to get paid. Mortgage’s don’t pay themselves.

Pat Frank
Reply to  Derg
October 24, 2022 8:27 am

Salary preservation is not the answer, Derg. Academic scientists have tenure. Few of them speak out.

My experience is most of them believe the foolishness because they trust other scientists to be ethical and competent.

Virtually all climate scientists are not competent — they’re untrained to evaluate data integrity — and some of them are unethical.

The real question is why the APS and ACS are willing collaborators in pseudoscience. I’ve emailed them. They remain silent.

If the APS spoke out, it would be over. But instead they tout the AGW crock, with equations that look impressive but offer no theory of climate.

I’d love to see them testify under oath.

Reply to  Pat Frank
October 24, 2022 6:07 am

It gets even worse. I’ve started to notice MSM articles which refer to things like “84%” as a very large number, but don’t enumerate 84% of what.

Jim Gorman
Reply to  Pat Frank
October 24, 2022 8:11 am

Thank you for a succinct statement concerning the present state of so-called climate SCIENCE.

These so-called scientists won’t even mention a Standard Deviation calculation for the distributions they are using let alone show a calculation of how one is obtained! An average or mean without an SD is a worthless number.

I’ve never seen a paper that deals with a temperature series even discuss the statistical difference between samples and a population. I’ve never seen one explain the difference in statistical inferences derived from a population and distribution statistics obtained from samples.

So-called climate scientists can’t even be bothered to make their series coincide with equinoxes and solstices. Heck let’s just split winter/summer between years so we can use simple year based time series!

None have ever heard of significant digits rules. Just make believe that we can create measurement resolution out of thin air by the mathematical process of calculating an arithmetic average.

As you say, the measurement uncertainty is usually waived away by the use of the Law of Large Numbers. They ignore the possibility that each and every measurement device can have a different “true value” which is never dealt with in the computation of an average. Just average, say 100 numbers from different devices at different locations and voila, you get Zero Uncertainty.

Pat Frank
Reply to  Jim Gorman
October 24, 2022 11:39 am

I’m guessing all that grinds on you even more than it does me, Jim. In your field, climate science sort of incompetence would kill people.

Now that I think about it, the incompetence of climate scientists is killing people, The manufactured excss of Winter fuel poverty deaths, for example.

Imagine a criminal referral of Michael Mann, Gavin Schmidt and Jim Hansen for criminal malfeasance and intentional homicide. Not to say grand theft.

Given the material fact of their demonstrable betrayal of science in the cause of AGW, I’d surmise such an indictment might succeed.

Reply to  Pat Frank
October 24, 2022 1:59 pm

I’d surmise such an indictment might succeed.

I doubt they will live long enough to face the music.

Suki Manabe will die as the recipient of the 2021 Nobel prize in physics for his contribution to climate modelling. He accepted the award with a graceful smile. The incompetence can be sheeted back to his contribution.

Hoyt Clagwell
October 23, 2022 10:47 pm

ZEIT: Are you saying that global warming is not a problem?
Stevens: “It’s a huge problem, partly because we know so little about its actual impact.”

Reminds me a bit of the Mueller investigation of Russian Collusion with Donald Trump.
‘We have no evidence that collusion happened which is why the investigation is so necessary.’

Reply to  Hoyt Clagwell
October 24, 2022 12:24 am

Stevens: “It’s a huge problem, partly because we know so little about its actual impact.

Comedy gold!

AGW is Not Science
Reply to  Mike
October 25, 2022 3:28 am

And from what black hole of profound stupidity does the notion that a WARMER climate is BAD come from?!

Only in the up is down fantasy world of “climate science” is something so utterly idiotic accepted as being ‘correct.’

Chris Wright
Reply to  Hoyt Clagwell
October 24, 2022 4:02 am

The more I think about that statement the more nonsensical it seems to be.
Actually, we know a huge amount about global warming’s impact – because it’s been proceeding for well over a century.
Since 1900, when the planet warmed about one degree, these things have happened:

The planet has become significantly greener. A major NASA study showed that the main reason was increased atmospheric CO2. The second reason was – oh, the irony! – global warming.
Human wellbeing has dramatically increased e.g. the OECD human wellbeing index.
Deaths from extreme weather have fallen dramatically.
When properly adjusted for GDP growth, no increase in the costs caused by extreme weather.
Food production (e.g. food per head of population, agricultural productivity) have increased dramatically.
In many cases (give or take a pandemic) the most dramatic rate of improvements have occurred in this century.
These are the impacts of global warming. In contrast the Little Ice Age (about one degree of global cooling) was a terrible time for humanity. If it had not been for the modern global warming we would still be in the depths of the LIA.
Stevens has it the wrong way around. No global warming would have been a huge problem.
All the signs are that the global warming we have enjoyed since 1900 has been a huge, huge benefit for humanity and the planet.

Reply to  Chris Wright
October 24, 2022 6:21 am

You describe the past when global warming was good news
The future is going toi be different
Global warming will only bring bad news
How do I know that?
Because scientists say so !

AGW is Not Science
Reply to  Chris Wright
October 25, 2022 3:29 am


We have a winner!

Peta of Newark
October 24, 2022 12:42 am

Time for a flurry of decimal point errors, check this pls

Quote:”Stevens: If you distributed all the condensed water in the atmosphere evenly around the globe, you would get a water film that is only two tenths of a millimeter thick.

Lets ignore the misspelling of metre, what does he mean there?

Lets take atmospheric weight as 5e18kg
Take average water content as 2% by volume and say that a water molecule is half the weight of an Oxygen molecule – so water contributes 1% by weight.
Thus there will be 5e16kg of water aloft, in the Troposphere mostly, on average.

Take Earth surface as 5e14 square metres gives 100kg per square metre or = 100mm thickness – not 0.2mm

How much ‘gravity’ do we attach to this error?
It’s a factor of 500

I’d assert, because I also want to rule the world, that Fifty Thousand Trillion tonnes one fug of a lot of gravity
Where does it put his temperature calculations, his education, his thought processes? Is he even awake?

We’ll also try but it’s difficult, to ignore his Cause & Effect error,
Clouds are manifestations of Climate and Weather – They Do Not Cause It

Last edited 3 months ago by Peta of Newark
Reply to  Peta of Newark
October 24, 2022 1:58 am


The 2% water vapor is only in the first hundred meters of the atmosphere. The higher in the atmosphere, the lower the water vapor content.

They also have an estimate of the water level if all available water would condense at the surface:

“If all the water vapor in the air at a particular time were to condense and fall as rain, it would amount to a depth of only about 2.5 cm. This is called precipitable water. Because water vapor is not evenly distributed globally, there would be about 5 cm near the equator and less than one tenth as much at the poles. The average precipitation over the globe is about 1 m annually, so there must be a rapid turnover of water in the air; the average water molecule spends about 9 days in the air before precipitating back to the surface.”

Anyway, your calculation is much nearer to reality (factor 4) than Stevens one (factor 125)…

Reply to  Peta of Newark
October 24, 2022 2:05 pm

You have misread what was written. He was referring solely to the cloud component.

The average water column is 24mm or 24kg/m^2 averaged over the Earth’s surface.

It only takes 1mm of water as ice to reflect 50% of the sunlight and absorb 95% of all OLR for re-emission at whatever altitude it sits.

October 24, 2022 4:35 am

Sorry, I have a hard time believing that a liter of water can fit into a pint of beer. What a mess.

Reply to  Scissor
October 24, 2022 6:23 am

You have never been at the München beer festival (“Oktoberfest”), I suppose… A “pint” (a can of beer is a better translation…) is 1 liter there…

Last edited 3 months ago by Ferdinand Engelbeen
Pat Frank
Reply to  Ferdinand Engelbeen
October 24, 2022 8:37 am

Old saying: A pint’s a pound the world around.

Apparently a pint is 454 mL except in Manchster. And as the mistake concerns excess beer, I’d suppose no one is complaining.

Reply to  Scissor
October 24, 2022 6:31 am

See above, it should say “mug or stein” not “pint”.

Reply to  Yooper
October 24, 2022 7:36 am

It should say “1 liter” which is correct. But we should be mild: Only a few Brittains will know the meaning of “1 Maß”, a word which is mostly used only in Bavaria, South Germany.

michael hart
Reply to  Scissor
October 24, 2022 8:12 am

You beat me to it.
“But I’ve only drunk three pints, officer”.

October 24, 2022 6:16 am

An honest scientist. Well he and koonin make two anyway . Nice to hear some truth about the much quoted crackpots at the Potsdam institute , led by Germany’s Mikey Mann , Stefan rahmsdorf

Julian Flood
October 24, 2022 6:56 am

“it’s hard to get rid of clouds…”

Ten years ago enroute to Madeira I saw a huge area – literally tens of thousands of square miles – where some sort of pollution had smoothed the ocean surface and suppressed wave formation. Both of these effects will have got rid of clouds.

Ocean pollution by oil and surfactant is reality (see the SeaWifs satellite data) and further smoothing by oleaginous phytoplankton fed by sewage and farming run-off (see the current state of the Sea of Marmora) is occurring. Cloud cover will almost certainly be reduced. Surface albedo will fall.

Since we began using oil products on a large scale (1910) we have been reducing cloud cover with the obvious result of surface warming. Remember Wigley’s blip? Oil spills from the Battle of the Atlantic.

If you dump pollution onto the nearly three quarters of the Earth’s surface that’s what you’ll get.


Pat Frank
Reply to  Julian Flood
October 24, 2022 9:02 am

we have been reducing cloud cover

You don’t know that, and neither does anyone else.

Julian Flood
Reply to  Pat Frank
October 24, 2022 9:27 am

Write me a cheque for a couple of hundred million and we could do the experiment. Incidentally there are suggestions that low level cloud is reducing. Like everything in clisci there will be disagreements about that fact.


Pat Frank
Reply to  Julian Flood
October 24, 2022 11:17 am

So, you don’t know.

Cloud fraction can’t be measured to better than about ±10%. The incidentalists don’t seem to recognize resolution.

Julian Flood
Reply to  Pat Frank
October 25, 2022 5:24 am

Experiment. But first think about the situation from first principles.

1. What happens to the albedo of a water surface when it is polluted with light oil?*
2. What happens to the evaporation from a water surface when it is polluted with light oil?*
3. When a large water surface is smoothed by pollution, what happens to the generation of cloud condensation nuclei by breaking waves?

Come now, it’s not difficult.

*And what implications does this have for Professor Wigley’s blip?

Pat Frank
Reply to  Julian Flood
October 25, 2022 10:15 am

Physical speculation without the test of observed behavior is just philosophy, Julian.

Julian Flood
Reply to  Pat Frank
October 25, 2022 11:36 am

Assertion without thought is worthless. Let me try again.

Israeli fish farmers have used oil on their ponds to speed up spring warming.

Q1. Is this the practical application of empirical science or arrogant assertion?

Q2. If the former then does the SeaWifs data suggest that oil spills may contribute some warming.

Q3. Have you looked at the SeaWifs data and the controversy around Professor Wigley’s blip?


Pat Frank
Reply to  Julian Flood
October 25, 2022 1:26 pm

All just inference and assigned meaning, Julian.

Get the spill data — estimated areas, spill rates, and film duration — express the ocean surface in some physically adequate way including wind mixing and wave action on surface stratification and and their effect on an oil film.

Do the calculation. Include changes in surface albedo and EM thermal penetration.

Then make your case.

Science is theory and result, Julian. It’s not arrogance to point that out.

You don’t even have theory. It’s not arrogance to point that out, either.

Julian Flood
Reply to  Pat Frank
October 25, 2022 2:57 pm

First you guess. That’s Feynman’s recipe for doing science. Then you check your guess against data. If the data doesn’t match the guess then the guess is wrong.

All we’re getting from you is flat denial and a demand that the data collection be done. Yes, having made the guess the data does need to be done, but your denial also demands data. Maybe you have access to research funds (just a joke) but I don’t. However, spill data has been done which is why I suggested you look at SeaWifs – it’s old and no doubt things are worse now but it should give you something to think about. .

Let me give you one last chance before I dump you as a troll. There are 7 questions for you in my posts. Try to answer them – this will entail actually doing some research and thinking about some of the data. For example you will, if you are conscientious, find that the Sea of Marmora is warming at more than twice the average of ‘global warming’. You will read Ruf and Evans paper where they thought they were measuring microplastic pollution but found they were looking at smooths. Reduction of albedo when water is smoothed has been measured – I’m on my mobile so I can’t point you to it but it will come up if you search. They used tanks and introduced oil IIRC.

Finally, let me define the term ‘answer them’. This does not mean producing more bafflegab, just respond in plain English. And do try to concentrate – if you were serious you would have looked at SeaWifs if nothing else.


Pat Frank
Reply to  Julian Flood
October 25, 2022 9:06 pm

Your questions are just a diversion, Julian. You claimed to have knowledge. You have none.

On having that established, you’ve become abusive.

October 24, 2022 11:00 am

The dissipative structure of the atmosphere is defined by the amount of sensible and latent heat transfer from surface to TOA. This is the bulk of upward flux in the atmosphere. The remainder is by IR radiation via the windows.

The bulk of net heat transport, or conversion, is by evapotranspiration to latent heat, followed by condensation to sensible heat aloft. The conversion efficiency is defined by surface moisture availability and the availability and quality of Cloud Condensation Nuclei CCN.

In total this defines convective efficiency K. Convective efficiency is driven by the phase changes of water. A slower water cycle reduces convective efficiency. A rapid water cycle increases convective efficiency.

This proposes there is in fact no net transport of IR within the atmosphere itself. Net IR transport can only occur to space. Any IR broadband radiation emitted from the liquid and solid drops in cloud are sourced in latent flux from the surface, and may be more free from there to transport heat to space.

Any perturbation of surface moisture availability, or to the quality and abundance of CCN, impacts this conversion efficiency. Conversion of net radiation at the surface, to latent heat, into sensible heat aloft, has an efficiency ranging from 5-95% depending on these factors.

When there are more CCN and suitable surface moisture, the atmosphere becomes more opaque and the heat transfer mode in the lower atmosphere shifts into more convective mode. Heat transport efficiency from the surface is improved, and albedo is increased. e.g. moist tropics. This represents highly efficient heat dissipation process.

With fewer CCN, or less surface moisture, the atmosphere becomes more transparent and the heat transfer mode shifts into more radiative mode. e.g. hot and cold deserts. Any desertification of the earth system, natural or human caused, shifts the flux characteristics and efficiency.

Cloud blocking IR windows is an instantaneous process and should not be considered to be net warming. Clouds do not cause net warming by inhibiting radiation, as their very existence has been sourced by cooling the surface. Furthermore, with increased convective efficiency, greater condensation of vapor, the atmosphere is dehydrated above the cloud top, allowing greater flux of heat from cloud top to OLR.

The western edge of most continents is typically more desert than the east. This, due to prevailing winds and the eastern sourcing of biological CCN from the continents. The western coasts do not have the luxury of these highly effective biological CCN, and exhibit more desert characteristics.

An experiment to run with satellite is to observe the change in cloud top temperature for a change in surface temperature, a la methods of Eschenbach. My suspicion is that the change in cloud top temperature i.e. ~ OLR in a moist place place, will far exceed that of the change in surface temperature. For example, I suspect an increase in the order of at least 2 or 3 in cloud top compared to surface temperature. This, due to the increased net convective transport. A 0.5K increase in surface temperature may result in a 1-2K increase in cloud top temperature. This represents increased transport efficiency to OLR.

For these reasons it is perfectly conceivable that cloud do not have any positive feedback effect to a radiative forcing alone. For they simply modify the flux mechanisms, from more or less radiative to more or less convective within the lower atmosphere.

However, any perturbation to surface moisture availability or to the abundance and quality of CCN will have massive impacts on heat flux regimes.

October 24, 2022 12:47 pm

From the Blog at Rules of the Lebensraum game with no CO2 Climate Crisis.

1.The earth has now reached a population level which has generated a battle for Lebensraum, i.e. energy and food resources, in Ukraine. The associated covid pandemic, and global poverty and income disparity increases, threaten the UN’s Sustainable Development Goals. During the last major influenza epidemic in 1919 world population was 1.9 billion. It is now 7.8 billion+/ – an approximate four fold increase.

The IPCC and UNFCCC post modern science establishment’s “consensus” is that a modelled future increase in CO2 levels is the main threat to human civilization. This is an egregious error of scientific judgement.  A Millennial Solar ” Activity” Peak at 1991  correlates with the Millennial Temperature Peak at 2003/4 with a 12/13 year delay because of the thermal inertia of the oceans. Earth has now entered a general cooling trend which will last for the next 700+/- years.
Because of the areal distribution and variability in the energy density of energy resources and the varying per capita use of energy in different countries, international power relationships have been transformed. The global free trade system and global supply chains have been disrupted.

Additionally, the worlds richest and most easily accessible key mineral deposits were mined first and the lower quality resources which remain in the 21st century are distributed without regard to national boundaries and demand. As population grows inflation inevitably skyrockets. War between states and violent conflicts between tribes and religious groups within states are multiplying.

2 The Millennial Temperature Cycle Peak.
Latest Data (1)
Global   Temp Data 2003/12 Anomaly 0.26 : 2022/9 Anomaly 0.24 Net cooling for 19 years
Tropics   Temp Data 2004/01 Anomaly 0.22 : 2022/9 Anomaly 0.03 Net cooling for 19 years.
USA 48   Temp Data 2004/03 Anomaly 1.32 : 2022/9 Anomaly 0.59 Net cooling for 19 years.
There is obviously NO CO2 Caused Climate Crisis.
Earth’s climate is the result of resonances and beats between the phases of natural cyclic processes of varying wavelengths and amplitudes. At all scales, including the scale of the solar planetary system, sub-sets of oscillating systems develop synchronous behaviors which then produce changing patterns of periodicities in time and space in the emergent temperature data. The periodicities pertinent to current estimates of future global temperature change fall into two main categories:
a) The orbital long wave Milankovitch eccentricity, obliquity and precession cycles. These control the glacial and interglacial periodicities and the amplitudes of the corresponding global temperature cycles. 
b)  Solar activity cycles with multi-millennial, millennial, centennial and decadal time scales. 
The most prominent solar activity and temperature cycles  are : Schwab-11+/-years ; Hale-22 +/-years ; 3 x the Jupiter/Saturn lap cycle 60 years +/- :; Gleissberg 88+/- ; de Vries – 210 years+/-; Millennial- 960-1020 +/-. (2)
 The Oulu Galactic Ray Count is used in this paper as the “solar activity ” proxy which integrates changes in Solar Magnetic field strength, Total Solar Insolation , Extreme Ultra Violet radiation, Interplanetary Magnetic Field strength, Solar Wind density and velocity, Coronal Mass Ejections, proton events, ozone levels and the geomagnetic Bz sign. Changes in the GCR neutron count proxy source causes concomitant modulations in cloud cover and thus albedo. (Iris effect)
Eschenbach 2010 (3) introduced “The Thunderstorm Thermostat Hypothesis – how Clouds and Thunderstorms Control the Earth’s Temperature”. 
Eschenbach 2020(4) in  uses empirical data from the inter- tropical buoy system to provide a description of this system of self-organized criticality. Energy flow from the sun into and then out of the ocean- water interface in the Intertropical Convergence Zone  results in a convective water vapor buoyancy effect and a large increase in OLR This begins when ocean temperatures surpass the locally critical sea surface temperature to produce Rayleigh – Bernard convective heat transfer.

 Short term deviations from the solar activity and temperature cycles are driven by ENSO events and volcanic activity.
comment image
Fig 1 Correlation of the last 5 Oulu neutron cycles and trends with the Hadsst3 temperature     trends and the 300 mb Specific Humidity. ( 5,6 )     The Oulu Cosmic Ray count in Fig.1C shows the decrease in solar activity since the 1991/92 Millennial Solar Activity Turning Point and peak There is a significant secular drop to a lower solar activity base level post 2007+/- and a new solar activity minimum late in 2009. In Figure 1 short term temperature spikes are colored orange and are closely correlated to El Ninos. The hadsst3gl temperature anomaly at 2037 is forecast to be + 0.0
………………………….. See more at link above

October 24, 2022 2:17 pm

It is not just the static effects of clouds already in existence (albedo effect reflecting away incoming sunlight or greenhouse effect of absorbing infrared from the Earth’s surface and re-emitting some back toward the surface, but also the dynamic process creating clouds.

As per Willis E’s several discussions of the transport of heat not by IR radiation, but evaporation at sea surface followed by upwelling of water vapor to high altitude above much CO2, where the heat energy is released by condensation, and much heat then radiated to space.
Current climate models focus too much on radiation and ignore the massive convection of heat away from the surface, especially via thunderstorms in the tropics.

October 24, 2022 4:22 pm

Climate sensitivity of 2.8C is poppycock. Physicists who have done the line by line calculations all show that CO2 doesn’t have a strong enough forcing to produce the strong positive feedbacks assumed in climate models. .5-.6C is what they get although it could be negligible compared to natural variability.

Adrian Mann
October 25, 2022 12:47 am

Stevens:  In my opinion, however, the contribution of the clouds is still overstated.
ZEIT: How great is it?
Stevens: Based on our latest measurements and advances in theory, I would say today: zero.”

Who is this idiot? Clouds have zero contribution to climate? He needs to get outside more. I suspect the real problem mis that clouds are too complex to model accurately so the best thing is to ignore them completely and concoct a reason for doing that.
I wonder what explanation he has for what has happened on Venus – obviously clouds have had precisely zero contribution to the climate there.

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