RealClimate: Unforced Variations: Oct 2026

Reply to JCM says 6 Oct 2026 at 10:31 AM
https://www.realclimate.org/index.php/archives/2026/10/unforced-variations-oct-2026/#comment-851408

Thanks for engaging sensibly with the material posted JCM. I read your comments carefully.

re “Hansen argues that the 0.5% decline in planetary albedo since early 2000s represents a 1.7 W/m2 increase in solar absorption, and that most of this MUST be climate feedback.”

and

“The point is whether or not the observation necessarily requires the larger feedback gain (Hansen) infers, or it it could equally be attributed to processes that have been misclassified as being entirely feedback.”

Yes, well that is one question. If you know what those processes could be I’d encourage you to reach to Hansen et al directly via Columbia-as such things cannot be settled nor investigated on a blog.

I’d like to add relevant points are made throughout the linked documents I included. I cannot address all of them in posts to RC or even attempt to correct all the general misunderstandings that have arisen from Hansen’s papers and articles. I only address a few leaving it to interested people to go look for themselves what’s there, and has always been there despite the public distortions.

eg found in To Understand and Protect the Home Planet 27 October 2023

1) “Our paper may be read as being critical of IPCC. But we have no criticism of individual scientists, who include world-leading researchers volunteering their time to produce IPCC reports. Rather we are questioning whether the IPCC procedure and product yield the advice that the public …. need to understand and protect their home planet.”

[ a shame that approach is not replicated in kind ]

2) Note the >Three-pronged analysis. …. vs IPCC relies solely on GCMs

3) ” Aerosol climate forcing results in part from the effect of aerosols themselves on incoming solar radiation, but mainly from the effect of aerosols as condensation nuclei for cloud drops. Increased aerosols result in smaller cloud drops (because the supply of water vapor is limited), which in turn causes clouds to be brighter (higher reflectivity) and longer lived (thus increasing global cloud cover).:,
https://www.columbia.edu/~jeh1/mailings/2023/HomePlanet.2023.10.27.pdf

KM Note: So there is negative aerosol forcing; negative cloud feedbacks from aerosol reductions; plus negative cloud feedbacks from the global temperatures now rising to a level where they are having an impact on negative cloud feedbacks as well. None of this is accurately being Modelled- but the albedo ceres ohc and eei are all implying it’s far greater than the models imply.

Note — already mentioned by let’s repeat it because it is critical to understand the issues at hand:
4) “Thus, in addition to higher climate sensitivity, the Faustian payments that come due as we clean up air pollution are greater. In the absence of measurements of aerosol climate forcing, the magnitude of the observed change of Earth’s radiation budget in the regions of heavy ship traffic indicates that aerosol models are likely underestimating the effect of aerosols on clouds.”
https://www.columbia.edu/~jeh1/mailings/2023/HomePlanet.2023.10.27.pdf

KM Note: This a point that pretty well everyone, including the distinguished professors such as Michael Mann either overlooked, or misunderstood, or simply got very wrong, in 2023 and ever since – instead assuming what he and Leon meant was that the IMO 2020 cuts in SO2 emissions was a primary driver for aerosol reductions and therefore equally a major cause of the “shocking Bananas warming spike”in 2023-2024 GMST

NO! They were never suggesting that. They were raising the bigger issue based on the limited but available and credible evidence from the Data the combined effects of aerosol, cloud and CERES Albedo changes shows “that CMIP/IPCC aerosol models are likely underestimating the effect of aerosols on clouds”

And that that was a BFD! And now we have the Satellite Data that as first glance appears to be CONFIRMING Hansen et al claims in Ice Melt and Pipeline and all their articles since 2023 are in fact correct-or at least far more accurate than the assumptions included in the Black Box CMIP/IPCC GCMs modelling parameters–and they are not the only ones asserting this rational conclusion. Sooner or later something is going to break!

5) “Measurement of aerosol climate forcing thus requires precise global monitoring of cloud and aerosol microphysics. Whether NASA would measure the aerosol climate forcing was a contentious issue beginning in the late 1980s, primarily because the observations required sampling of the seasonal and diurnal cycles of cloud cover that could best be achieved from a pair of relatively inexpensive small satellites, which we dubbed Climsat. … As a result, the aerosol climate forcing has not been monitored and aerosol forcing is, in effect, a free parameter in climate models.”

6). “In Pipeline, we obtain an indirect inference on aerosol climate forcing via well defined knowledge of climate sensitivity (from paleoclimate) and accurate satellite measurements of Earth’s energy balance. Especially because of the absence of monitoring of the aerosol climate forcing, it is crucial that the precise measuring of Earth’s radiation budget
continue. If NASA is not going to make such plans, it is crucial that ESA (the European
Space Agency) take up the challenge.”
from https://www.columbia.edu/~jeh1/mailings/2023/HomePlanet.2023.10.27.pdf

KM Note: And they did; with an EU and US satellites launched in 2024- the results are ONLY NOW starting to come in-as referenced above. Hansen mentions this issue repeatedly for over 40 years; plus the 2 X monitoring satellite launches which failed eg in Faustian Bargain of 2013:

7) “The tragedy of this science story is that the great uncertainty in interpretations of the climate forcings did not have to be. Global aerosol properties should be monitored to high precision, similar to the way CO2 is monitored. The capability of measuring detailed aerosol properties has long existed, as demonstrated by observations of Venus

The requirement is measurement of the polarization of reflected sunlight to an accuracy of 0.1%, with measurements covering the spectral range from near ultraviolet to the near-infrared at a range of scattering angles, as is possible from an orbiting satellite. Unfortunately, the satellite mission designed for that purpose failed to achieve orbit, suffering precisely the same launch failure as the Orbiting Carbon Observatory (OCO). Although a replacement OCO mission is in preparation, no replacement aerosol mission is scheduled. “

and

7) Aerosol growth slowed in the 1970s with pollution controls in the U.S. and Europe, but accelerated again after ~2000.”
https://www.columbia.edu/~jeh1/mailings/2013/20130329_FaustianBargain.pdf

KM:
Whatever the real data is (or was) China Asia drove higher aerosols post 2000; then in 2013 China began to cut back rapidly; but India then increased it massive coal fired power expansion still ongoing; IMO reduced shipping emissions in 2015, and again more severely in 2020. And none of the existing emissions data is accurate; it is all inferred instead.

Meanwhile all this time the CGMs CMIP modelling has been guessing the amount an effects of aerosol forcing and more importantly the Cloud dynamics globally and specifically to do with aerosol changes on cloud feedbacks. As well as ECS in a manner contrary to the 3-pronged approach Hansen suggests is more accurate and valid; given the available evidence BEFORE the hard aerosol/cloud Data finally comes from the two satellites referenced.

Theoretically they know there must be an impact but they do not know with any real certainty in models nor the IPCC exactly what those might be. The modeling is a black box — Hansen’s inferences and modelling is an open book based on Physics and acknowledging the extent of uncertainty.

NOTE in 2023>
“In Ice Melt, we used the three-prong analysis to show that continued high emissions would cause shutdown of the North Atlantic Overturning Circulation (AMOC) and the Southern Ocean Overturning Circulation (SMOC) this century, possibly by mid-century, and sea level rise of several meters on the 50-150 year time scale. In Pipeline we reveal how the reticent community, with full reliance on models (that tend to be unrealistically insensitive to
freshwater injection) alone, could manage to dismiss this result, and, instead, conclude that
there was less than 1 percent chance of shutting down AMOC, even with high GHG emissions.”
https://www.columbia.edu/~jeh1/mailings/2023/HomePlanet.2023.10.27.pdf

KM: Soon after this was said, multiple papers and public commentary was arriving pointing out exactly the SPEED and RISK Hansen pointed to over a decade before. It appears history is repeating itself.

The real issue/s is not if Hansen’s “numbers” are spot on or not. The Issue is finally acknowledging that the UNCERTAINTY embedded within the CMIP/IPCC Models and all their outputs is off the charts and unreliable for forming rational policy responses.

That’s is what he has always been saying. That’s the POINT.

Because 2c of warming is coming at us faster than anyone expects — like an out of control train.

And QUOTE
Scientific Reticence.
” The concluding words of the title of the Ice Melt paper were “…2°C global warming is highly dangerous.”

The paper had been heavily peer-reviewed by four referees and by the wider community via the open review process. One of the four referees – an IPCC lead author – had strong objections to the paper, but he was overruled by the other three referees and the editor.

However, the editorial board intervened, insisting that the paper could not be published unless we changed the last words of the title from “…2°C global warming is highly dangerous” to “…2°C global warming could be dangerous,” an almost meaningless conclusion.

The editor – an exceptional scientist – agreed with our position, but was unable to prevail.

Finally, so what does Zeke Hausfather now have to say about this subject matter?

The Coolest Year for the Rest of Our Lives? with Zeke Hausfather | TGS 236

1:07:30 Nate: https://www.youtube.com/watch?v=_QtEETGsCw0&t=4078s
“You’re all completely in agreement that the world is warming and headed to north of two degrees Celsius. What do we really not know yet? What is the remaining uncertainty in the whole climate ecological, planetary boundary space? And what is your midpoint currently, and what do we not know, do you think? ”

Zeke: There’s really three big uncertainties that future warming comes down to.

1) The first is what we do as humans, right? How do we increase emissions? Do we decrease emissions? That’s maybe half the uncertainty in future warming at this point.

2) (Second) there’s how does the Earth’s biogeochemistry respond to our warming. How does that affect greenhouse gas concentrations, and the carbon cycle feedbacks.

3) And (thirdly) the final piece is this question of climate sensitivity. How do all the feedbacks in the climate system around water vapor, clouds and albedo, et cetera, respond to that warming?

And if we put all of them together, um, you know, we get a pretty wide range of future warming possibilities.
[end quote]

KM: Summarized concisely as: Climate Science does not know-but James Hansen has been alerting the world to this lack of scientific knowledge for over 20 years now.

It appears to me that maybe Zeke “could be” about to wake up. What do you think?