One would think that James Hansen—once lionized as the father of modern climate alarmism—might bask in the limelight after a fresh round of histrionics about Earth hurtling toward a “point of no return.” Instead, we find him on the pages of his latest blog-style polemic, “Large Cloud Feedback Confirms High Climate Sensitivity”, complaining that he’s being ostracized by the very media and institutions he helped train to bark on command every time the CO2 concentration ticks up another ppm.
“A strange phenomenon occurred… almost uniformly, these reports dismissed our conclusions as a fringe opinion… Are there important repercussions for the public… indeed, for the future of all people? The answer… is ‘yes.’”
https://www.columbia.edu/~jeh1/mailings/2025/CloudFeedback.13May2025.pdf
One might suggest that after decades of theatrics, people have simply stopped buying tickets to the same show.
But let’s not be hasty. His newest round of publications deserves scrutiny, not for its recycled gloom, but for the increasingly acrobatic logic and interpretive liberties embedded within.
The ‘Big FXcking Deal’ and the Cloud Feedback Feedback
At the heart of Hansen’s thesis is the observed decrease in Earth’s albedo—the fraction of sunlight reflected back into space. Hansen pegs this decline at 0.5% over the last two decades, translating to a 1.7 W/m² increase in absorbed solar radiation. This, he insists, proves that cloud feedback must be large and positive, confirming an equilibrium climate sensitivity of 4.5°C ± 0.5°C for doubled CO2.
“Earth’s albedo… has decreased about 0.5%… we described this change as a BFD… because it has staggering implications.”
https://www.columbia.edu/~jeh1/mailings/2025/CloudFeedback.13May2025.pdf
Hansen claims that the albedo change cannot be explained by greenhouse gases alone, nor by the “direct” effects of aerosols. Instead, the culprit must be changes in clouds, which in turn, must be a climate feedback.
“The only substantial climate forcing affecting Earth’s albedo is the ‘indirect’ aerosol forcing… most of the 1.7 W/m² increase of energy… must be due to climate feedbacks.”
https://www.columbia.edu/~jeh1/mailings/2025/CloudFeedback.13May2025.pdf
This is an assertion in search of a mechanism. He observes warming and cloud changes, assumes causation from CO2 induced warming, and calculates a feedback strength that—surprise—matches his hypothesis. That’s the very definition of motivated reasoning.
Aerosol Forcing as Narrative Spackle
In his longer “Acceleration” paper, Hansen admits the models are not calibrated against measured aerosol data but against presumed outputs. This gap is pivotal—he uses it to boost both climate sensitivity and his own sense of clairvoyance:
“Aerosol forcing and climate sensitivity were wedded in an inappropriate shotgun marriage… we now seek to disentangle and expose their relationship with simple computations.”
https://www.tandfonline.com/doi/full/10.1080/00139157.2025.2434494#abstract
He attributes most of the albedo decline to changes in cloud behavior, calling it “proof” of a strong, positive cloud feedback. But what’s lacking is a mechanistic, independently validated causal chain linking CO2 increases to these cloud dynamics. The leap from observation to attribution is made with equations and assumptions, not with direct evidence.
The models can fit any historical curve if aerosol parameters are set freely. And that’s precisely what Hansen does—he adjusts the inputs to make the models scream “catastrophe,” then declares the match to observed warming a triumph of insight.
The self-pity is especially ripe in the Cloud Feedback piece:
“Criticisms… did not address the physics in our three assessments… Instead, criticisms were largely ad hoc opinions, even ad hominem attacks… How can science reporting have descended to this level?”
https://www.columbia.edu/~jeh1/mailings/2025/CloudFeedback.13May2025.pdf
Hansen’s argument structure is fundamentally circular: he assumes a high-sensitivity system, interprets ambiguous data to reinforce that view, and then treats the match as confirmation. That’s not how robust hypothesis testing works.
Here we have the scientist as prophet, rejected not because his models are unconvincing, but because the masses and the media are insufficiently enlightened. It’s not that his arguments are speculative—it’s that the world is failing him.
Hansen’s paper is not so much a scientific analysis as it is a sermon. Every ambiguous result is resolved in favor of catastrophe. Every observational artifact is “proof” of more warming to come. Meanwhile, dissent is brushed off as ignorance, and uncertainty is never allowed to cut both ways.
His “proof” of a large cloud feedback rests on little more than a curve fit, a CO2 narrative, and a theological certainty in the apocalypse. As a rhetorical performance, it has its good points. As a scientific argument, it’s hollow.
And that, to borrow from his own words, is the real “BFD.”
Steve Milloy of Junk Science notes:
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Is it warmer than it was in the ’70s? Yes it is. Does that constitute a looming crisis? No it doesn’t.
Severe weather is not on the increase, food production increases every year. Sea level continues to go up ever since it was first recorded in 1807, and acceleration is is almost nil. The polar bears are enjoying a population increase. Coral reef bleaching isn’t caused by warmer water, any map of coral distribution around the world tells you that. Forest fires are natural, and in urban areas the destruction is from poor forest management. Glaciers have been receding since the end of the last ice age.
There is no “it”. Some places have warmed, some have cooled, some have remained relatively static. Averaging all of those together is scientific fraud.
Warmer winters here in Milwaukee. Everywhere else,
I have to rely on the published records..
I hear you, but many of the published records are tainted by urban growth, and do not properly represent non-urban temperatures. Thus, I must admit that a large city like Milwaukee will be seeing higher temperatures.
I have much more faith in the satellite data. I think I see even there that temperatures are creeping up – but that is quite normal in a post glacial period such as we live in. Nothing unusual.
Urban warming indeed. More concrete, asphalt and people has to have some impact.
Absolutely.
Plus more energy generated and consumed. All of that enters the atmosphere as thermal energy.
Everyone now has a heat pump that evacuates higher temperatures outside 24 hours a day when necessary.
“Everyone”? Some of us have avoided being politically correct.
Is it every winter? just some?
On a positive note, he likes nuclear energy.
Nothing about a scam artist is positive. The man has made a career out of scamming the public. In a sane world, he would be behind bars.
How much less sunlight does all the recent greening from increased CO2 reflect? If it had been desert, I’d guess a fair amount.
I still want someone more talented than me to cook up a Grim Fairy Tale about Hansen and Greta.
If greening has increased by 15-20% then the mass of Earth’s chlorophyll is absorbing 15-20% more sunlight than it used to.
And that solar energy is not reaching the ground to be stored and later released when there is no sun. Greening cools the surface of the planet.
Forests are darker than most deserts.
Yes, absorbing more sunlight, reflecting less. But I am no climatologist. If that doesn’t matter, someone will say so in pretty clear language that even I can understand.
Fortunately, albedo is just a bit player in the complex world of climate. Climate Liar Hansen loves to use it, because it suits his purposes.
Technically it is averaged bond albedo. 25 km grids are not homogenous or even close to uniform.
What proof? Take off your shoes and socks. Go out and put one foot on the blacktop and the other on the grass.
“Hansen and Greta.”
I wish I had come up with that.
Terrific!
I was once told if you can’t dazzle them with your brilliance baffle them with your bullshit. I fear that is what is going on here. Hansen is a crackpot.
Talking about Death Trains, Climate Tipping Points and making predictions that do not happen lead people to believe the crackpot definition.
Perhaps Dr. Hansen should read the climate4you website of Ole Humlum under the climate +clouds button. There he will learn 1) Total cloud cover has been declining for several decades, 2) When cloud cover increases they have an overall cooling effect and 3) When they decline the earth’s albedo declines causing the Earth to warm.
Just like taking your hat off in the Sun, results in local head warming. The LSH (local skull heating) effect. If you are alarmed by this sudden increase in temperature, put your hat back on.
+10
But then again, there are the effects of evaporation of sweat and its associated skin cooling that have to be considered if one wants the full story.
Tell us all about it, then.
What? . . . you on a mental disability list or something?
What. . . . you trying to be disparaging or something?
Watch out for skin cancer.
Thanks. Strangely enough, I just had a melanoma chopped out from a part of a limb that sees little sun. My “Celtic” skin apparently makes me more susceptible.
How racist is that!
/humor off
Hansen seems to be saying that increased CO2 causes less cloud cover, which then results in warming..
According to climate alarmists like Hanesn, CO2 climate warming is supposed to be caused by CO2 initially, which supposedly causes an increase in water vapor, that increases warmth even more. An increase in water vapor would lead to an increase in cloud cover, not a decrease.
An increase in cloud cover would lead to cooling.
There is no evidence that CO2 has any measurable effect on water vapor or cloud cover.
Hansen used to say the year 1934, was the hottest year in the United States being 0.5C warmer than the 1998, temperature high point.
But after 1998, cooling set in and Hansen, in an effort to defend climate alarmism, started saying 1934, was not as hot as 1998. Hansen is very flexible with the facts when it comes to climate alarmism. If he has to lie to sell the climate crisis narrative, then he will lie.
Hansen is the “Flim-Flam” man. The Snakeoil salesman. The Carnival Barker.
He can’t prove a thing he says about CO2 and the Earth’s climate.
The earth is a thermal energy system.
Oceans are the heat sink (store and release thermal energy)
The clouds are the governors.
Yes, it is much more sophisticated and complex.
The Earth has cooled over the last four and a half billion years, continuous sunlight, atmosphere, CO2, clouds, water, notwithstanding.
Am I disparaging Hansen if I refer to him as delusional, or a complete nutter? Do I care? Maybe he thinks the same about me!
Experiments are often wrong.
I’m sure Hansen doesn’t even know you exist.
In that case, no harm. Why do you bother mentioning it?
I am banking on Earth’s relationship with the Sun being the primary cause of lower cloud.
The coldest year in Earth’s recorded history would have been around 1700. On May 14th in 1700 Earth was 179.000km further from the Sun than 14th May 2025. Daily solar intensity at 60N on May 14 1700 was 411.7W/m^2. This year it is 413.6W/m^2.
I suspect the increasing March to June solar intensity in the NH is reducing cloud. Because there is a lot of land in the NH and it is not as wet as oceans.
Then of course there is much of Europe and China working hard to reduce the spread of airborne water from oceans to land by building row after row of wind stillers from the continental shelf to coastal ridges; knocking over forests to install the stillers. The resulting desertification is a sure way to reduce moisture on land. More desert is a sure way to ensure less cloud.
Rick Will:
I believe that the correct explanation for the reduction in cloud cover is the reduction in the amount of industrial SO2 aerosols in the troposphere due to “Clean Air” and “Net Zero” activities.
SO2 aerosols (micron sized droplets of Sulfuric Acid, H2SO4) have a VERY strong affinity moisture, and it is used as a drying Agent.
With fewer SO2 aerosols present, there are fewer moisture nucleation sites, and fewer clouds are formed, causing temperatures to rise. However, this causes increased evaporation (and droughts), and areas of the atmosphere become saturated with moisture, causing the formation of Atmospheric Rivers, which randomly (?) release their water in torrents of rain.
It all ties together!
Regarding Hansen’s observation of reduced albedo, that is being caused by the greening of the Earth by higher CO2 levels, which have no other climatic effect.
Clouds have increased just north of the Equator. That is function of the NH heating and more ocean reaching the regulated limit of 30C
?ssl=1
So any theory you might come up with regarding cloud has to explain the increased cloud between 1S and 7N.
Burl’s theory also has to account for the cyclical nature of the Earth’s climate, where it warms for a few decades, and then it cools for a few decades, and then the process repeats, and his theory does not account for this cyclical movement.
ANY theory of the Earth’s climate has to account for the cyclical nature of the Earth’s climate.
The “Clean Air Act” and Netzero” did not apply in the past, since they didn’t exist then, yet the climate of the past behaves just the way the climate of the present behaves. Therefore, the “Clean Ari Act” and “NetZero” and SO2 are not relevant when trying to describe the cyclical nature of the Earth’s climate.
Tom Abbott:
Earth’s climate is NOT cyclical in nature.
EACH warming or cooling episode can be associated with changing levels of SO2 aerosols in the atmosphere, ,primarily due to to the presence or absence of volcanic eruptions prior to the Industrial Revolution, and a mixture of volcanic eruptions and changing levels of industrial SO2 aerosol pollution afterwards
It is cyclical in nature due to orbital mechanics and precession.
Yes, levels of S02 have an effect, but not the driver.
There no one magical answer to the complexity of the earth thermal engine.
So my question is: given the number of large volcanic eruptions of late, why has the planet not cooled if it is simply SO2.
Sparta Nova 4:
As noted in my reply to Tom Abbott, our climate is NOT cyclic. ALL changes are due to changing levels of SO2 aerosol pollution in the atmosphere.
Temperatures ALWAYS rise when there are 2 1/2-3 years between VEI4 or larger volcanic eruptions, since all of their volcanic SO2 aerosols have settled out.
The last such eruption was Hunga-Tonga in Jan 2022, which is now more than 3 years ago.
Burl, explain the cooling that took place from the 1940’s to the 1980’s using your SO2 theory. That’s about 40 years of cooling, so your theory would have to show very large volcanic eruptions about every two years during that whole period of time. Do you have such evidence?
Please explain the movement of the U.S. regional temperature chart using your SO2 theory. Show how volcanic eruptions managed to lower the temperatures by 2.0C during this time period.
The U.S. regional chart (Hansen 1999) is below. When you can explain the U.S. chart to me using your SO2 theory then I’ll be onboard. Not until.
Tom Abbott:
“Explain the cooling that took place from the 1940’s to the 1980’s”
Actually, the 1950’s. Much of the 1940’s were warmer, because of the lack of VEI4 volcanic eruptions between 1937 and 1943
Industrial SO2 aerosol levels are are tracked by the Community Emissions Data System of the Pacific Northwest National Laboratories, an arm of the Dept. of Energy.
For the period 1950 to 1980, levels of industrial SO2 aerosol pollution rose from 56 million tons to 141 million tons, an increase of 65 million tons, and this increase raised concerns of the return to another Ice Age.
The above is shown on the annual mean of your graph.
“Actually, the 1950’s. Much of the 1940’s were warmer, because of the lack of VEI4 volcanic eruptions between 1937 and 1943.”
You’re not looking at the same chart I’m looking at. Hansen 1999 shows cooling during the 1940’s, not warming.
“For the period 1950 to 1980, levels of industrial SO2 aerosol pollution rose from 56 million tons to 141 million tons, an increase of 65 million tons,”
You need to put this in the context of volcanic eruption equivalents.
And you also need to explain the similar cooling that took place from the 1880’s to the 1910’s, when there was no industrial increase in SO2. The 1910’s were just as cool or cooler than the late 1979’s. The 1880’s were just as warm as the 1930’s.
Let continue this in the Open Thread tomorrow. This article is getting too old.
“Earth’s climate is NOT cyclical in nature.
EACH warming or cooling episode can be associated with changing levels of SO2 aerosols in the atmosphere”
The Earth’s climate IS cyclical in nature. The only real data we have on the Earth’s climate shows it is cyclical.
Here is the only real data we have about the Earth’s climate, the Regional, Written, Original temperature records. They all show the cyclical nature of the Earth’s climate. If you want to reject the facts, that’s your problem. The facts are in the 600 graphs in the link.
https://notrickszone.com/600-non-warming-graphs-1/
You are comparing your SO2 levels to the movement of the bogus, bastardized Hockey Stick chart. If your theory fits the bogus Hockey Stick chart, then your theory does not represent reality, because the bogus Hockey Stick chart does not represent reality. It’s as simple as that.
Your theory does not match the REAL movement of the Earth’s climate, as depicted in the regional temperature charts.
Rick Will:
You have to be kidding!
Comparing 2001 to 2023 HAS to be cherry-picking.
You might be right, but that graph needs more supporting evidence.
Seems a bit like a “Wet roads cause rain” analysis….
Hansen is a copycat selling climate snake oil. When NASA lost funding as the Apollo (moon landing) program ended in 1972, the planetary atmospheres group was told to switch to earth studies. In 1976 they copied the fraudulent one dimensional radiative convective (1-D RC) model published by Manabe and Wetherald (M&W) in 1967 and created global warming artifacts for 10 minor species including methane, CH4 and nitrous oxide, N2O [Wang et al, 1976]. Later, in 1981 Hansen et al copied the slab ocean construct described by Manabe and Stouffer in 1979. They used their 1981 1-D RC model to create a time series of warming artifacts that were ‘tuned’ to match a global mean temperature record. This provided the foundation for the pseudoscience of radiative forcings, feedbacks and climate sensitivity still used by the climate models today.
The equilibrium climate sensitivity (ECS) for the 1967 M&W model was 2.9 °C. The ECS for the 1981 Hansen et al model was 2.8 °C. Any climate model that has an ECS larger than ‘too small to measure’ is fraudulent. There is no need to look any deeper into the model configuration or model code. This needs to be established as a legal criterion for the identification of fraudulent climate models,
https://www.americanthinker.com/articles/2025/05/damage_claims_and_clawback_are_needed_to_stop_the_climate_modeling_fraud.html.
The climate modeling fraud is discussed in detail in the paper A Nobel Prize for Climate Modeling Errors.
Impressive!
The effort to attain positive feedbacks goes much further. This is one amazing piece I just realized. In theory the lapse rate should shrink by over 2% per Kelvin of warming. That is the theory represented in emagrams, but also serves as a base for climate models, like Santer et al 2005 shows.
That brought up a serious question. The GHE depends on the lapse rate. If the atmosphere was isothermic and the lapse rate zero, there would be no GHE. It is the tropospheric lapse rate that defines the difference in temperature between surface and (average) emission altitude, and thus Ts – Te = 33K. This GHE should accordingly shrink by over 2%. I arranged this graph to illustrate the issue.
That will make a huge negative feedback, exceeding all other positive feedbacks, turning all feedbacks combined equally negative. How would climate models not do that and have total positive feedbacks instead?
Feedback parameters in climate models are calculated assuming that they are independent of each other, except for a well-known co-dependency between the water vapour (WV) and lapse rate (LR) feedbacks
(AR6 p.978)
Physically LRF has to be determined by the change of the lapse rate, there is no other way. But this would inevitably result in a dominant negative feedback. So instead of following the physical necessities, they apply a “trick”. They just bundle it with WV feedback and hard code that the sum must be a postive feedback..
Positive feedback, as used by the climate idiots, is merely repackaged “runaway greenhouse effect.”
Good article.
Making assumptions about feedbacks, then assume it to be true, just to reinforce a narrative is suspect.
It is always dangerous to take the word of a zealot at face value, especially if scrutiny is not allowed.
A paper from Hansen is one of just TWO where the abstract states that human carbon dioxide is the dominant (over 50%) factor of dangerous global warming. This was out of 12,464 abstracts reviewed over a 21 year period (Cook et al, 2013-Quantifying the Consensus.) I noted that 7 of the 43 references were his own work, which is regarded as suspect. The second paper basically parroted the IPCC. It was basically an essay without actual hands-on work. 2 papers out of 12,454 over a 21 year period can hardly be regarded as an overwhelming 97.1% consensus. To make things even more interesting, if you go through Cook et al Quantifying the Consensus, keying in the search term “catastrophic” in to the level 1 endorsement (human CO2 is the dominant driver of global warming) for the entire data base has ZERO papers!!!!
To justify radical “climate action” it is essential that HUMAN CARBON DIOXIDE is the DOMINANT cause of catastrophic or dangerous global warming/ “climate change.”
If it is not the human component, then “climate action” is unjustified.
If it is not carbon dioxide, all the “curbing carbon emissions” is a waste of time and effort.
If it is not the dominant cause of the claimed climate issues-if nature has more effect than humans, radical “climate action” will be fruitless.
If the climate effects are not catastrophic or dangerous, then there is no point making radical changes in human behaviour. Danger is something humans and animals can cope with. Realistically, ONLY the catastrophic subset is truly significant.
It takes just 1 minute, 39 keystrokes and 9 clicks of the mouse to ascertain this. If you could not be bothered to spend that one minute to ascertain the validity of radical climate action, you don’t have much credibility.
Go to skeptical science (Cook’s page-you will see his cranky uncle logo)
Top row, drop down from consensus project to search abstracts. Click.
If you don’t select the years, it automatically searches through the entire data base. Click level 1 endorsement.
Search terms- dangerous, catastrophic. Out of the 12,464 abstracts reviewed over a 21 year period, there should be 12,102 papers with human carbon dioxide as the dominant cause of dangerous or catastrophic global warming. Do these simple steps for yourself. This is from the very database that Obama referenced for his famous tweet on May 17, 2013-“97% of scientists agree #climatechange is real, manmade and dangerous.”
Many people catastrophise this to believe human carbon dioxide is the overwhelming cause of catastrophic global warming. However, going through the actual definitive database has ZERO evidence. ZERO evidence in the entirety of climate science for 21 years-the time when climate policy was being formulated.
Even by Cook et al’s own admission, two thirds of the papers they reviewed the “abstracts” of TOOK NO POSITION on their “question” that was so mealy-mouthed that even many skeptical scientists might “agree.”
But somehow, by the “New Eco-Fascist Math,” 97% can “agree” even when 67% are “neutral.”
That so-called “study” was a farce from the beginning, and even the “97% of 33% was overstated as indicated by scientists whose papers were part of the study who said that their papers were misclassified as being “in agreement” when they were, in fact, neutral or even skeptical.
Making assumptions that CO2 is the “control knob,” then assume it is true, just to reinforce a narrative is suspect.
Agent Smith
CO2 is the input to the models and temperature is the output.
Seems a very obvious assumption built in.
One has to wonder if it is possible to model molecular interactions on a 25 km grid.
Are albedo meters available for purchase?
Per the above article, Hansen argues that a decline of 0.5% in Earth’s albedo over the last two decades due to reduced cloud coverage translates to a 1.7 W/m² increase in absorbed solar radiation.
Well, why doesn’t he put that claim “where the sun don’t shine”?
That is, he apparently ignores the effect of decreased cloud coverage in terms of increasing LWIR heat radiation to space during nighttime (and it applies during daylight as well).
Albedo effect on incoming solar radiation is only a small part of the science necessary to calculate/estimate if Earth’s net energy (actually power flux, in units of W/m^2) balance is positive or negative, and by how much.
Why am I not surprised that James Hansen overlooked this?
Hansen has been an alarmist tool of Al Gore and the Greens since at least 1988. He also sometimes behaves as if he’s an operative of the State Department and/or an HVAC repairman for Congress. He should have been charged with violations of the Logan Act long ago, as well as misapplication of the Laws of Thermodynamics.
I thought Hansen was disbarred or whatever it is they do to “climate scientists” (a self designated term). Hansen should be disbarred, thrown out, black balled etc. from publishing in accredited journals. Self promotion only goes so far, time to pull the plug.
Even if accurate, a change of one half of one percent in one variable out of many in a complex system is a deviation so slight as to be negligible.
Mr. Hansen, an excitable man with a histrionic personality, is a follower of the Fragile Earth school of thought, which holds that our planet is perpetually on the knife edge of perfect balance. Nudge it even a little and it slides into a doom spiral. It’s a common viewpoint among climate fanatics.
But this is nonsense If our planet were really so tender that it could be disrupted by a trifling change, it would have died of natural causes a long, long time ago, or never have come into existence at all. Clearly, the Earth is the opposite of fragile. It takes a licking but keeps on ticking.
It boggles me that a thing so obviously untrue could be the basis of the climate change movement, the longest-running mass psychosis in modern history.