It's the Ocean not the Atmosphere, dummy!

[Anomalism]

Albedo of a glaciating northern hemisphere or a deglaciating northern hemisphere. It's quite conventional. I don't understand how you aren't getting it.

That doesn’t address the key distinction in the argument: redistribution vs net energy change vs pacing mechanism. AMOC and other circulation changes can strongly shift regional heat, and albedo feedbacks can amplify global temperature changes once ice sheets are growing or shrinking.

However, neither mechanism alone explains why these transitions repeatedly occur in step with orbital variations in high latitude summer insolation over hundreds of thousands of years.

 

[ding]

No need for the condescension.

I don't know that you understand it.

That still doesn’t remove the energy-constraint issue.

What energy constraint issue?

The climate system doesn’t keep warming because it was cold.

Where did I say it did?

What’s actually happening in the standard framework is orbital forcing gradually changes summer insolation at high northern latitudes, which creates a small persistent imbalance in ice sheet mass. Once that imbalance favors retreat, feedbacks amplify it into a full deglaciation. The energy source is still solar radiation; the system is responding to a slowly shifting boundary condition, not self-propelled warming from past cold states.

I've yet to hear you explain it in any detail. You didn't mention any specific parameters or explain what they were at that time. Not to be condescending but saying orbital forcing is generic.

 

[Anomalism]

When it switches off it will be fully understood. Trust me. That's when the real science will begin and the hunt for the guilty will start. They will all be pointing fingers at each other saying they knew all along AGW was wrong but they were too afraid to speak out.

This is drifting away from science and into prediction of future revelation, which is where arguments stop being testable.

 

[Anomalism]

What were the orbital parameters at the end of the last interglacial period that made this happen?

At the end of the last interglacial, Northern Hemisphere summer insolation dropped mainly because of precession and a declining axial tilt.

That reduced summer melting enough that winter snow started to persist year after year. Ice sheets then began to grow, and feedbacks like higher albedo and lower CO2 amplified the cooling into a full glacial transition.

 

[ding]

This.ss drifting away from science and into prediction of future revelation, which is where arguments stop being testable.

How do you test orbital forcing? If you can't is that still science? There's physical evidence for ocean currents causing abrupt climate change.

 

[Anomalism]

I don't know that you understand it.

What energy constraint issue?

Where did I say it did?

I've yet to hear you explain it in any detail. You didn't mention any specific parameters or explain what they were at that time. Not to be condescending but saying orbital forcing is generic.

At the end of the last interglacial, Northern Hemisphere summer insolation dropped mainly because of precession shifting NH summer toward aphelion and a declining axial tilt.

That reduced high-latitude summer melting below the threshold needed to remove winter snow. Ice sheets started growing, and feedbacks like higher albedo and lower CO2 amplified the cooling into a full glacial transition.

 

[ding]

At the end of the last interglacial, Northern Hemisphere summer insolation dropped mainly because of precession and a declining axial tilt.

What does that mean exactly in real terms?

That reduced summer melting enough that winter snow started to persist year after year.

Is there evidence for that?

Ice sheets then began to grow,

Over how long of a period and what evidence is there for that?

and feedbacks like higher albedo and lower CO2 amplified the cooling into a full glacial transition.

No different than if heat stops being circulated from the Atlantic to the Arctic, right?

 

[Anomalism]

How do you test orbital forcing? If you can't is that still science? There's physical evidence for ocean currents causing abrupt climate change.

Orbital forcing is tested by comparing calculated changes in Earth’s orbit with independent geological records like ice cores and ocean sediments. These records show that ice ages and deglaciations tend to line up with changes in northern high-latitude summer insolation, and that temperature, ice volume, and CO2 change in consistent phase relationships with those cycles.

 

[ding]

At the end of the last interglacial, Northern Hemisphere summer insolation dropped mainly because of precession shifting NH summer toward aphelion and a declining axial tilt.

Can you provide some numbers?

That reduced high-latitude summer melting below the threshold needed to remove winter snow. Ice sheets started growing, and feedbacks like higher albedo and lower CO2 amplified the cooling into a full glacial transition.

Just like if the AMOC switched off, right?

 

[ding]

Orbital forcing is tested by comparing calculated changes in Earth’s orbit with independent geological records like ice cores and ocean sediments. These records show that ice ages and deglaciations tend to line up with changes in northern high-latitude summer insolation, and that temperature, ice volume, and CO2 change in consistent phase relationships with those cycles.

So a correlation. Not hard evidence like in the papers that discuss ocean currents causing abrupt climate changes.

 

[Anomalism]

What does that mean exactly in real terms?

Is there evidence for that?

Over how long of a period and what evidence is there for that?

No different than if heat stops being circulated from the Atlantic to the Arctic, right?

In real terms precession is the slow wobble of Earth’s axis that changes whether Northern Hemisphere summers occur closer to or farther from the Sun. Obliquity is the tilt of Earth’s axis, which controls how strong high-latitude summers are. At the end of the last interglacial, these combined so that Arctic summers received less peak sunlight, meaning less complete summer melting.

Yes, there’s strong evidence for this chain. Ice cores, ocean sediment oxygen isotopes, and sea-level reconstructions all show that after this orbital shift, ice volume increased and sea level fell over several thousand years. The “snow persists year after year” part is inferred from ice-sheet mass balance and isotope records showing sustained global cooling and ice accumulation.

It’s not the same as “AMOC stops circulating heat.” Ocean circulation changes redistribute heat regionally; orbital forcing changes the amount and seasonal distribution of incoming solar energy at high latitudes, which is what determines whether ice sheets can persist and grow in the first place.

 

[ding]

That still doesn’t explain the repeating, orbitally timed glacial cycles on its own. You’re describing internal amplification mechanisms, not what sets the long-term pacing.

In the standard framework, ocean circulation, ice extent, salinity shifts, and thermal gradients are responses and amplifiers within the system. The slow, repeating driver that nudges the system toward those thresholds is orbital variation in high-latitude summer insolation. Without that external pacing, the feedbacks you listed don’t naturally produce a 100k/41k-year global rhythm.

I don't accept your correlation though. I think it's bullshit. The south pole is just as susceptible to orbital forcing as the north pole.

 

[Anomalism]

Can you provide some numbers?

Just like if the AMOC switched off, right?

At the end of the last interglacial, summer sunlight in the Northern Hemisphere high latitudes dropped enough to matter for ice sheets, from precession shifting summer farther from the Sun and a 1° decrease in Earth’s tilt.

That reduced peak Arctic summer insolation by roughly 10–20% at critical times, enough to let winter snow survive summers and gradually build ice sheets over thousands of years.

An AMOC shutdown is different. It mainly redistributes existing heat regionally, while orbital changes alter the amount of summer energy reaching high latitudes.

 

[Anomalism]

So a correlation. Not hard evidence like in the papers that discuss ocean currents causing abrupt climate changes.

It’s not just a simple correlation. Orbital forcing is tested because it makes specific, testable predictions about timing and high-latitude summer sunlight, and those line up with ice cores and ocean sediment records showing ice, temperature, and CO2 changing in consistent phase relationships.

 

[ding]

In real terms precession is the slow wobble of Earth’s axis that changes whether Northern Hemisphere summers occur closer to or farther from the Sun. Obliquity is the tilt of Earth’s axis, which controls how strong high-latitude summers are. At the end of the last interglacial, these combined so that Arctic summers received less peak sunlight, meaning less complete summer melting.

Yes, there’s strong evidence for this chain. Ice cores, ocean sediment oxygen isotopes, and sea-level reconstructions all show that after this orbital shift, ice volume increased and sea level fell over several thousand years. The “snow persists year after year” part is inferred from ice-sheet mass balance and isotope records showing sustained global cooling and ice accumulation.

It’s not the same as “AMOC stops circulating heat.” Ocean circulation changes redistribute heat regionally; orbital forcing changes the amount and seasonal distribution of incoming solar energy at high latitudes, which is what determines whether ice sheets can persist and grow in the first place.

When will orbital forcing trigger the next glacial period?

 

[Anomalism]

I don't accept your correlation though. I think it's bullshit. The south pole is just as susceptible to orbital forcing as the north pole.

South Pole is affected, but it can’t drive the cycle.
Glacial cycles are mainly controlled by Northern Hemisphere land ice, because it can grow and collapse and strongly amplify climate change. Antarctica is already locked in ice and is more isolated, so it doesn’t respond in a way that can pace global ice ages.

 

[ding]

It’s not just a simple correlation. Orbital forcing is tested because it makes specific, testable predictions about timing and high-latitude summer sunlight, and those line up with ice cores and ocean sediment records showing ice, temperature, and CO2 changing in consistent phase relationships.

Testable to me means you can predict when the next glacial period will occur.

 

[ding]

South Pole is affected, but it can’t drive the cycle.

How has it been affected?

Glacial cycles are mainly controlled by Northern Hemisphere land ice, because it can grow and collapse and strongly amplify climate change. Antarctica is already locked in ice and is more isolated, so it doesn’t respond in a way that can pace global ice ages.

But it can melt, right? Just like the NH ice melts?

 

[Anomalism]

When will orbital forcing trigger the next glacial period?

We don’t know precisely, and it likely isn’t imminent on human timescales.

Under natural orbital cycles alone, the next full glaciation would be expected tens of thousands of years from now, because current orbital configuration keeps Northern Hemisphere summer insolation relatively high compared to glacial-start conditions.

 

[Anomalism]

Testable to me means you can predict when the next glacial period will occur.

Testable here means the theory correctly matches patterns in past climate data.

It doesn’t mean you can predict an exact date for the next glacial period, because internal feedbacks and today’s greenhouse gas forcing also affect the timing.