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:
Related
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.