It's the Ocean not the Atmosphere, dummy!

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If orbital forcing were a red herring, we'd need an alternative explanation for why glacial-interglacial cycles follow the 100,000 year eccentricity cycle, why deglaciations align with northern hemisphere summer insolation peaks,

First of all correlation does not prove causation and they haven't always followed a 100,000 year cycle. For the last 1 million years it's been a 100,000-year cycle, but before that it was a 41,000-year cycle (i.e. 1 million years ago to 2.7 million years ago).

and why D-O events themselves are confined to glacial periods.

They aren't necessarily. The Eemian and Holsteinian interglacial periods were punctuated by sudden cooling events. The Purfleet period featured extreme climate instability, including rapid, severe cooling "Heinrich" events. The Arousa/La Bouchet/Aveley interglacial was a warm interglacial which was characterized by high climatic instability and rapid fluctuations rather than a prolonged, stable warm climate. And of course, you already pointed out Younger Dryas. All climate fluctuations over the past 3 million years are being driven by the same thing. Heat circulation from the Atlantic.

 

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What mechanism do you think drives the glacial-interglacial cycle if not orbital forcing?

I've told you already. Heat circulation from the Atlantic to the Arctic. Ocean currents.

 

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Calling them glaciation and deglaciation misses what they actually are. They're regional temperature oscillations, not ice age transitions. Greenland warms and cools rapidly, ice sheets don't fully collapse and regrow. That's the key distinction.

D-O events don't contradict orbital forcing because they're operating at completely different scales. Orbital forcing explains why Earth was in a glacial state for 100,000 years in the first place. That's the background condition that allowed D-O events to happen. The AMOC shifts that drive D-O events are internal climate system dynamics that occur within that orbital forced state.

D-O events happen during glacials, not interglacials. If AMOC shifts alone could drive glacial-interglacial cycles, we'd see D-O-style oscillations triggering ice ages during warm periods too. We don't. The current interglacial has been relatively stable for 11,000 years despite ongoing ocean circulation variability. Why? Because the orbital configuration doesn't support extensive northern hemisphere ice sheet growth right now.

You still haven't answered the question. If orbital forcing is a red herring, what mechanism explains the 100,000.year glacial-interglacial cycle? What explains why deglaciations consistently align with peaks in northern hemisphere summer insolation? D-O events can't explain that pattern because they're confined to glacial periods and operate on millennial timescales, not a 100,000 year cycle.

Also,.the graph you posted showing D-O events was created by the same climate scientists you're arguing are wrong about everything. Those ice core records, the isotope analysis, the dating methods, all done by researchers who accept that orbital forcing drives glacial cycles and that AGW is real. If you trust their data enough to use it as evidence, why reject their interpretation of what it means?

It's the same mechanism. At the end of the day it is driven by density differences; salinity and thermal. Both of which are temperature dependent. So if it is as you say orbital forcing is causing the planet to warm. Which according to the IPCC's graphics, isn't happening now so why would it in the past? According to me, it is the natural cycle of glaciation and deglaciation in the Arctic that is driving temperatures. As the northern hemisphere deglaciates the planet is returning to it's pre-glacial temperature. At some point density differences trigger a change in ocean currents and the cycle begins anew.

 

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And yet the ocean and atmosphere's increase in heat have tracked the GHG's rise. In fact, this has been the case throughout geological history;

Correlation does not prove causation which is especially true when the correlation is broken as it was after the industrial revolution. The data clearly shows the correlation is broken.

Prior to the industrial revolution CO2 was a function of temperature. Temperature was not a function of CO2. The mechanism was CO2 solubility in water which is temperature dependent. Temperature changed so CO2 changed. CO2 didn't cause the temperature to change. Prior to the industrial revolution there was no mechanism for CO2 to change other than temperature.

 

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Orbital (Milankovitch) changes warm the planet by only a small direct amount—on the order of ~0.1–0.3 W/m² globally, which translates to well under 1 °C of direct global-average warming. Milankovitch cycles alter seasonal solar energy. Globally averaged, the change in total solar energy is tiny. Eccentricity changes Earth–Sun distance, but the annual global-mean solar input barely changes. Obliquity and precession redistribute sunlight between seasons and latitudes, not total energy.

By contrast when the AMOC switches off the change in temperature in the Arctic is violent and ABRUPT.

To argue orbital forcing is driving AMOC switch off would mean that orbital forcing is warming the planet before but not now because it is temperature which causes the AMOC to switch off because it is temperature which alters the salinity/density of the thermohaline circulation which drives the AMOC.

 

[Anomalism]

It's the same mechanism. At the end of the day it is driven by density differences; salinity and thermal. Both of which are temperature dependent. So if it is as you say orbital forcing is causing the planet to warm. Which according to the IPCC's graphics, isn't happening now so why would it in the past? According to me, it is the natural cycle of glaciation and deglaciation in the Arctic that is driving temperatures. As the northern hemisphere deglaciates the planet is returning to it's pre-glacial temperature. At some point density differences trigger a change in ocean currents and the cycle begins anew.

Ocean circulation is a redistributive mechanism, not an external energy source. AMOC shifts can strongly change where heat goes, especially regionally, but they do not explain the pacing of glacial cycles by themselves.

You're saying the Atlantic drives it, but that just moves the question back one level. What drives the long-term state changes in the circulation system itself?

The reason orbital forcing remains central is because the timing problem still exists.

The transition from dominant 41,000-year cycles to ~100,000-year cycles matches changes in ice sheet dynamics and orbital modulation.

Deglaciations consistently occur near peaks in northern summer insolation.

Ice volume, CO2, sea level, and temperature evolve in phase relationships predicted by orbital pacing plus feedbacks.

Ocean circulation alone does not explain that astronomical synchronization.

And yes, abrupt variability also occurred in some interglacials. Nobody disputes that. But instability within interglacials is not the same thing as explaining the existence and pacing of the glacial-interglacial cycle itself.

Also, you said...

"temperature changes alter density differences, which alter circulation."

Fine. But what initiated the large-scale temperature changes repeatedly over hundreds of thousands of years with orbital periodicities matching Milankovitch cycles?

If the answer is "internal ocean variability," then you need a mechanism explaining why that variability repeatedly tracks orbital geometry over geological timescales instead of behaving quasi-randomly.

And there's another issue...

The current warming pattern is not just North Atlantic redistribution. The oceans globally are accumulating heat. Measured ocean heat content has risen substantially. Redistribution can cool one region and warm another, but it cannot explain a long-term increase in total system heat without a forcing imbalance.

The IPCC graphic point cuts against your argument. Orbital forcing today is slightly toward long-term cooling, not warming. Yet temperatures are rising anyway. That's one reason greenhouse forcing stands out so strongly in attribution studies.