Hello Dean,
You will be happy with CIMP7 end dates because if go to 2500.
About CDR, I agree with you. It’s a big problem on the communication side : by design scenarios HL, ML and L leads to the same goal : 1.5°C. The layman will conclude that whatever we do before 2070 we have the same result : 1.5°C.
Authors say “ML and HL scenario assumptions risk exceeding limits of prudent use of sequestration capacity” and “challenge current estimates of geophysical feasibility”.
“However, they are included […] to ultimately serve as narratives for interactive CDR deployment experiments in Earth System Models (for example, in CDRMIP), and scenarios in which the limits of CDR are challenged are useful for identifying where Earth System Models are unable to deliver the scenario negative emissions rates (for example if bioenergy yields in the ESM are lower than the IAM estimates).”

Great question – The ScenarioMIP paper refers to the “return to coal” theory in this sentence, with appropriate references: “Clearly, the cumulative amount of fossil fuel use in the High emission scenario is considerably larger than the estimated total reserves (known deposits that are extractable at current prices and technologies) (Bauer et al., 2016; Rogner, 1997).”
To learn more about the theory, and why it is flawed, and certainly should not have been the single basis for RCPs and SSPs, see this: https://www.rff.org/publications/working-papers/evaluating-the-learning-by-doing-theory-of-long-run-oil-gas-and-coal-economics/

RC: Concentrations [CO2] lag temperature in ice cores, and variations in MLO measurements lag global and SST temperatures.

MS: You refer to 2 separate issues:

1. Ice cores. You are correct that at the beginning of each deglaciation period, temperature increase precedes natural CO2 increase. This is because temperature increase at the beginning of the deglaciation period is entirely caused by long-term cyclical changes in Earth’s orbit and tilt.

But as the oceans warm, they begin to release CO2, and as the albedo of ice covered land changes, the oceans warm faster and the exposed deat vegetation on land rots, and more CO2 is added to the atmosphere.

At that point, and from then on, temperature lags CO2. Only about 5% of the subsequent temperature increase is still caused by the orbital and tilt changes of the planet. The other 95% lags the natural CO2 increase.

And recall that we know CO2 absorbs and re-emits infrared light. We know it because we measure it in the lab; we have been measuring it in the labe since the late 1800s, and the atmosphere in our lab experiments is composed of the same gases as the atmosphere outside.

2. MLO CO2 measurements vs seasonal temperature changes in the northern hemisphere.

No. You cannot compare these directly; there are too many other factors involved. But the long term CO2 increase measured at MLO is leading the long term global average temperature increase.
—–

Those are your 2 issues with CO2 being the forcing of most of our current warming. But your attempt to refute the greenhouse effect using Greenland ice cores is wholly irrelevant, because it is about geological time and natural CO2 increase due to natural warming — over geological time. We are not discussing geological time here. We are discussing the last 150 years, during which atmospheric CO2 has increased by more than 50%, almost all from buring fossil fuels, but also some from deforestation.

Changes in orbital and tilt parameters continue at their glacial pace (pun intended), but those changes are actually be causing Earth to cool slightly right now, But the planet is not cooling; it is warming, and it is warming well within the range predicted by greenhouse theory, given the measured increase in anthropogenic CO2 in the atmosphere.

There is no competing explanation that fits all or even most of the data, and you don’t even have an explanation. You have an alleged cycle and an idea about the tidal effect on the sun caused by occasional alignments of the Jovian planets. You want this tidal effect to be causing increased sun spot numbers and TSI.

Google AI says this about the maximum tidal effect of ALL the planets on the sun, not just your Jovian ones:

“Even when all Jovian and inner planets perfectly align, the maximum physical height of the resulting solar tide is less than a few millimeters to 1 meter.”

That’s on the sun, Robert, so even if we take the worst case, the ratio of a 1 meter wave on the surface of the sun to the entire sun is about the same as the ratio of my fingernail to the entire sun.

And you still don’t have a mechanism. Here is what Google AI says about your idea:

Do Planetary Tides Cause Sunspots and TSI Changes?

Whether these miniscule tides influence the 11-year sunspot cycle and Total Solar Irradiance (TSI) is a subject of ongoing debate in astrophysics:

1. The Conventional View: Internal Magnetic Dynamo (Mainstream Consensus)

The mainstream scientific consensus states that planetary tides are far too weak to cause sunspots or alter TSI. Sunspots and solar cycles are driven internally by the solar dynamo—a process where the Sun’s differential rotation twists its internal magnetic fields. The electromagnetic forces moving the Sun’s conductive plasma are orders of magnitude stronger than any planetary gravitational pull.

2. The Planetary Hypothesis: The “Resonance Push” (Alternative Theories)

Some researchers argue that while the planetary tidal force is weak, it acts as a synchronized pacemaker. Astrophysicists like Frank Stefani have modeled how the recurring alignment of Venus, Earth, and Jupiter every 11.07 years could provide a tiny, rhythmic “tug”.

In these models, this tiny force acts like someone pushing a child on a swing at the exact right moment, utilizing resonance to influence the Sun’s alpha effect and stabilize the 11-year sunspot cycle rhythm. However, peer reviews of similar studies (such as those by Abreu et al.) frequently conclude that these statistical correlations are mathematically insignificant or accidental.

So your alleged cycle plus your allusion to tidal effects on the sun caused by planetary alignments has been/continues to be considered, but it also has been/continues to be rejected, because the solar dynamo explanation is better. Your research has not changed that outcome at all that I can see. You haven’t contributed anything new.
—–

RC: In the short term, using sunspot data, my model predicted a slight decline in temperatures starting in 2016 and extending to almost 2040. If temperatures continue to rise over that time period, I’ll be wrong, at least for the sunspot model.

MS: IOW, your model has been wrong for 10 years, but you’re gonna give it another 14 years?

RC: If temperatures stop rising, and concentrations continue to rise (which they will) will you accept that the CO₂ hypothesis has been proven false? If not, how can the hypothesis be falsified?

MS: No. Recall that we KNOW CO2 absorbs and re-emits infrared light. We know because we measure it in the lab. It occurs exactly as known laws of physics say it must. The laws of physics won’t stop working in my lifetime, so if global average temperature stops rising before I say “Happy trails,” I will ask why and look for the cause, which will have to be something that produces enough global cooling to counter the global warming we KNOW is being forced by the increasing CO2.

And the CO2 forcing is no longer a hypothesis; it is a scientific theory.

RC: The 3560-year repetition in climate can be falsified if someone can show there isn’t a repetition, or, they can explain the cycle using something other than the Jovian planets.

MS: No. We don’t have to falsify your cycle, because you have no mechanism. You have to explain the mechanism for how Jovian planet alignments that cause a small tidal effect on the surface of the sun can cause TSI to increase, and then you have to explain, not only how that increased TSI is THE cause of the current warming, but also how it negates the warming we know is forced by all the anthropogenic CO2.

RC: I do have an “idea” as to how the Jovian planets are linked to variations in solar activity. The Sun and planets form a resonant system with the Sun containing over 99.8% of the mass. Jupiter is less than 0.1%. Some put the core as having a bit less than half the mass of the Sun.

The core floats in the radiative zone. If the core has resonant modes, as it most certainly does, those resonances would modulate gravity and also acoustically modulate the density in the radiative zone and by extension the energy flux at the convection zone. More energy, faster convection, shorter sunspot cycles. So it’s possible that the Jovian planets, like sunspots, are just a another proxy for variations in solar activity.

MS: I look forward to reading your peer-reviewed paper. Until then, you’ve got bupkus.

Gavin, thank you for the clear technical post. I agree that swapping scenario sets for a new CMIP round is normal, not a scandal, and that RCP8.5 remains physically plausible for the century if carbon cycle feedbacks and societal inertia are accounted for.

But two deeper problems are not addressed here, and they are not technical—they are cultural.

First. The low scenarios in CMIP7, like those in AR6, depend on CDR at scales that do not currently exist and may never exist. That is not a minor uncertainty. That is a structural assumption baked into “policy-relevant” pathways. When those pathways are communicated to the public and policymakers as the 1.5°C or 2°C futures, the CDR assumption is almost always elided. That is not science. That is wish fulfillment dressed in GCM clothing.

Second, and more fundamentally. The modern climate science establishment operates with the same unexamined sense of authority that John Locke once invoked to “subdue the earth”—later manifest destiny, then industrial capitalism, then the technocratic confidence that we can model our way out of a crisis created by that same mindset. Five centuries of slavery, colonial wealth extraction, world wars, and now planetary boundary overshoot, all justified by some claimed right to manage, predict, and control.

The CMIP process is not immune to this. The arrogance is quieter now—expressed in overconfidence in multi-century model integrations, in CDR fairy dust, in the casual dismissal of RCP8.5 as “implausible” by people who have never run a coupled carbon-climate model, and in the implicit assumption that this generation of scientists is not repeat the errors of the last 500 years.

Nature does not care about our scenarios. Nature will find balance. It always does. The question is whether that balance includes a stable Holocene-like state for human civilization, or a hothouse trajectory with meters of sea level rise over millennia. The models are tools, not oracles. And the people running them are not exempt from the critique we would apply to any other powerful institution: who authorized you to subdue the earth with equations?

This is not science’s finest hour. It is just the latest chapter in a very old story of masculine, imperial, technocratic, divine arrogance and superiority. More polite, peer-reviewed. Still wrong in the same fundamental ways that brought us to this point in Earth history.

Mankind: thy name is Vanity.

I read https://rogerpielkejr.substack.com/p/no-rcp85-did-not-become-implausible where you said “RCP8.5 — and indeed all of the RCP and SSP scenarios — had a single point of failure in its assumption of a return-to-coal. This assumption alone settles the question of plausibility. A scenario requiring five times proven coal reserves is not plausible by any standard.4”, went to reference 4: “The new HIGH “what if?” scenario in the ScenarioMIP ensemble continues to employ the return-to-coal hypothesis, as acknowledged by its creators:….”
That only refers to the HIGH scenario for fossil fuels (I’m guessing not just coal), and not what you said:”and indeed all of the RCP and SSP scenarios — had a single point of failure in its assumption of a return-to-coal.”
So then I went to “The Scenario Model Intercomparison Project for CMIP7 (ScenarioMIP-CMIP7)” at https://gmd.copernicus.org/articles/19/2627/2026/ and again I can’t find anything that backs up your “return-to-coal.” statement. Where do I read about the “return-to-coal.” for all the other scenarios? Was it for older CMIP scenarios?

True, but you miss stating the point outright. The point of blaming Jupiter and the Sun is that that means he can assert there is no human contribution to climate change, of course. Basically he’s screaming “SQUIRREL!!!”

Not surprising, really, since the Post has for decades promoted global warming denial in its editorial pages, and has normalized, sanitized and legitimized the fossil fuel industry’s bought-and-paid-for stooges by falsely branding them as “skeptics”.

in Re to Paul Pukite, 19 May 2026 at 11:56 PM,

https://www.realclimate.org/index.php/archives/2026/04/a-reflection-on-reflection/#comment-848208

Dear Paul,

Thank you for your correction.

1) Should / will I read your book?

I am afraid that at least from the geophysical chapters of your book, I would hardly understand more than their titles.

2) Background of my question

Your posts on Real Climate about your tidal hypothesis raised my feeling that your book has not raised much attention in the expert community yet, and I thought that by your blog and by your posting herein, you try to fix this deficiency. Furthermore, I had a feeling that the support for your hypothesis, e.g. by comparison of extreme tides predicted by your theory with historical tide records in specific ports is a new stuff, not comprised in your book.

3) Correction of my question

I should have rather asked if the hypothesis described in your book attracted the attention and acceptance that you mean it deserves. If not, was it a good idea to present your new ideas and your evidence therefor in your book?

I thought that since scientific journals became the standard way for publishing new results and/or hypotheses, books serve rather as secondary sources, summarising information previously published in journals.

Greetings
Tomáš

https://x.com/matthewgburgess/status/2057192401907945872

Beneath all the heated rhetoric, I don’t think most academics on various sides of the scenarios issue are actually that far apart. For example, I think your “But wait!” section is pretty spot on above (and echoes things we’ve called for in our various scenario papers).