by Kirby Schlaht
What really does set the global climate state? The Million Year Ice Core Project (MYIC) (Follow on BlueSky), has been underway for several years, preparing to drill the oldest continuous ice core record from Antarctica. The project is a major element in the Australian Antarctic Program, led by the Australian Antarctic Division and other national and international collaborators to answer that very question.
Now, in 2025, the Australian Antarctic Division is leading one of the most ambitious and challenging scientific projects undertaken in Antarctica – the quest to drill an ice core containing over a million years of Earth’s climate and atmospheric history. This continuous climate record will help solve a long-standing mystery about the timing and duration of past “ice ages” detected in marine sediment cores (Fig. 11). These sediment cores with their fossilized foraminifera reveal a proxy temperature record that indicates about one million years ago the cycle of “ice ages” shifted from a regular 41,000 year glacial-interglacial period, to a cycle every 120,000 years.
A prevailing theory is that declining atmospheric CO2 levels were the cause of the longer, colder ice expansions. The new million-year ice core record might provide the essential atmospheric gas record to test this theory.
We can see in the 1998 Vostok ice core data from Antarctica (below) that temperature leads the way with CO2 following by hundreds to thousands of years. At its simplest, this indicates that temperature not CO2 drives the climate change. What then drives the temperature change? Some might say “it’s too complicated”. I beg to differ.
Antarctic EPICA Dome C ice core temperature proxy data below is shown with Milankovitch orbital cycle forcing. While much correlation is discernable, it makes sense that higher obliquity increases insolation especially to the polar regions driving warmer temperatures and interglacials while lower obliquity provides less insolation, cooler temperatures and glacial expansion. Now, superimpose the 20k-year precession cycle where the effective obliquity angle could be modified by as much as 1 degree and the result is a confluence of high obliquity, high precession, and high eccentricity providing the insolation changes sufficient to break the cold feedback loops (water vapor and ice-albedo) of the previous glacial expansion period. After a 20k year interglacial, high eccentricity, low obliquity and low precession drive temperatures lower where the cold ice-albedo feedback loop takes hold and catches us in its hundred millennia icy grip.
Do the ice cores extracted from Greenland show the same climate variability and timing as Antarctica? The proxy temperature record below shows us the fine detail of a glacial-interglacial period from Greenland. The previous interglacial, the Eemian, around 120 thousand years ago, progressed to the follow-on glacial expanse period. As eccentricity and obliquity just begin to fall, we see temperature “jumps” (D-O events) in closely packed time regions. These hot blips are probably solar activity driven warm-ups. We can see the short duration of the events and a long cold recovery. As we approach the midway point of glacial expanse, we see some gaps where no temperature spikes occur. These correspond to low obliquity periods (there are 3 of these during the ice expanse). The periodic solar cycles that gave us the hot events during high obliquity cannot break through the colder low obliquity feedback wall. When high obliquity returns so do the undampened solar spikes. Continuing on to the confluence of high obliquity, high eccentricity where precession produces a series of significantly hotter northern hemisphere summers when the Earth is near its closest distance to the sun (apogee). This results in breaking the ice-albedo feedback and subsequent deglaciation and a 20k year interglacial period – this is our interglacial called the Holocene. We should not expect the fundamental planetary orbital processes that drive the Ice Age climate oscillation to all of a sudden be rendered ineffectual by a few parts per million of some trace atmospheric gases. To foretell the future of climate change then – in 10k years or so, with eccentricity still high and obliquity going low, precession produces a period where northern hemisphere summers occur near apogee with high eccentricity and low obliquity resulting in those summers getting a little warmer while southern hemisphere summers become significantly colder near perigee resulting in rapid sea ice expansion and the next 100k year glacial expanse period.
With this sampling of both polar regions, and the exceptional resolution from Greenland, we see the same basic climate shifts. During the last 800 thousand years or so, a seeming pattern of climate variability of 20k year warm interglacials followed by 100k year cold glacial periods has persisted. During the glacial expanse we see solar activity driven warming peeking through the high obliquity window with low obliquity shading and damping any solar influence. Great! Seems to explain a lot. Seems pretty clear. Milankovitch cycles and cold feedback loops. Does not explain the Great Shift though. Why did the periodicity of the glacial-interglacial cycle change from 41k years to 120k years around a million years ago (Fig. 11)? The 41k year obliquity cycle seems to predominate in the early Pleistocene glacial-interglacial cycle – for 2 million years. What changed? Further, what had set the earth’s climate to oscillate in the first place?
The Great Shift
From The Story of Climate Change, I lay out the paradigm shifting ideas we can call the cosmic ray/cloud hypothesis (Svensmark). This cosmic radiation/ionization/cloud formation concept might now be expanded. Accepting the centrality of cosmic ray ionization in cloud modulation, and with observational and mechanistic support, I propose that climate is sensitive to the amount of lower tropospheric ionization caused by high energy Galactic Cosmic Rays (CR). More high energy radiation in the lower atmosphere means more ionization, more aerosols, more and whiter low-level clouds, thus cooler climates. Alternately, less radiation in the lower atmosphere means fewer clouds driving warmer climates. We can call this integrated process the cloud-albedo effect.
The long geologic timescale modulation of Earth’s tropospheric cloud cover and global temperature are driven in a top-down process beginning with high energy galactic radiation variations originating in Earth’s galactic orbit location within the Milky Way spiral structure. This produces low frequency climate responses: 50-million-year Hothouse periods with lower CR flux as we transit an inter-arm space and 100 to 200 million year Icehouse periods with higher CR flux as we cross a Milky Way spiral arm. Our solar system also experiences galactic orbital oscillatory out-of-plane perturbations. The plane polarized galactic cosmic radiation intensity is then further modulated by our in-and-out-of-plane orbital motion. This acts as a secondary driver of higher frequency climate responses: periodic 30-million-year warming-then-cooling-then-warming cycles. This signal is superimposed on the background spiral arm radiation signature.
The galactic radiation intensity sets the baseline temperature from which all other drivers vary. For the last 50 million years of our galactic orbit, we have been transiting the Sagittarius spiral arm. The increasing baseline spiral arm radiation leads us further into the colder chambers of the Icehouse. At the same time, the radiation intensity and temperature have been oscillating up and down in unison with our in-and-out-of-plane motion. We are now fully in-plane with cosmic rays at maximum. This promotes increasing tropospheric cloud-cover which can cool the Earth further. A glacial Ice Age can occur if the spiral arm radiation-driven baseline temperature of the planet falls to a critical minimum upon which our vertical galactic orbital oscillation places us nearly fully in-plane. Now we are vulnerable. Other shorter-term forces such as planetary orbital dynamics, ice-albedo feedback, plate tectonics, volcanism, solar activity, or proximate celestial events could push the Earth into a full-blown glacial Ice Age or “Snowball” scenario.
Here we are, in the middle of the Pleistocene Ice Age. So far, over the last 3 million years our climate has oscillated between cold and icy glacial climates and warm interglacial climates. The 41k year glacial-interglacial period driven by planetary obliquity dominated the Pleistocene for two million years. One million years ago the glacial-interglacial period switched to the current 120-thousand-year period. What has changed over the last 3 million years? The answer should be obvious, the temperature has changed. A million years ago the global temperature was colder than before and is ultimately colder today. One million years ago we were approaching the galactic plane and the bottom of this Pleistocene cold climate trough. The closer to the bottom the colder we got. So cold in fact, that high obliquity alone could not break the ice-albedo feedback loop. All three planetary orbital parameters – obliquity, eccentricity, precession – must act together in a 120-thousand-year cycle to melt our icy tomb to finally bask in a high obliquity sun once again – into the next warm interglacial.
Where are we now?
One million years after The Great Switch, here we are now. Our current climate state is warm interglacial. We have passed the interglacial optimum temperature (high obliquity) and are experiencing a continuing cooling as obliquity moves lower toward the next glacial inception point about 10 thousand years from now, where high eccentricity and low obliquity will drive rapid sea ice expansion and the next 100k year glacial period. In a wider view, assuming we are currently at the midpoint of the Pleistocene Ice Age and at the bottom of this current cold climate trough, symmetry suggests that we will experience slowly warming temperatures as we proceed out-of-plane with glacial-interglacial cycles becoming more interglacial dominant until finally dissipating in another 3 million years or so.
Finally
I am not sure that a new extensive Antarctic ice core record would change my thinking when it come to the ultimate drivers of global climate but it might be enlightening to visualize The Great Switch climate variability from a southern hemisphere perspective through Oxygen-18 isotope temperature proxies from water ice.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
I’ll pass on being the first to comment, because I’ll only display my ignorance about what the weather was like in Antarctica millions of years ago.
Especially on a mid-November day about afternoon tea time.
Please don’t hold it against me or diss me for my uneducatedness.
I throw myself on the mercy of the Climate Court.
My guess is that it was a lot warmer in Antarctica before it was covered in the odd km or three of ice. Global cooling, do you think?
Fun thing, first taught me by now Prof. Emeritus Lindzen of MIT when he critiqued June 2012 the penultimate climate chapter of my then not yet published ebook The Arts of Truth, concerning Svalbard. (His critique resulted in a long two page Svalbard footnote).
Antarctica was once a lot warmer simply because it wasn’t then over the South Pole. Plate tectonics. The Drake passage only opened about 33mya.
See, this is why I come here.
To get me some gold nuggets of info about how this space conveyance we call Earth got to its current state of being.
Facts are aways stranger than fictions.
Personally I’ve always liked this particular graph with the Temperature Delta T scaled to match the CO2 concentration.
?ssl=1
It does however create a problem.
Utilizing the same scale, if you extend the CO2 concentration up to 420 ppm (current concentration) then the Delta T side would need follow up to +12°K. This would, by extension, indicate that our current Temperature anomaly should be at least 10°K warmer than measurements indicate.
“It does however create a problem.”
It is my understanding that no vegetation can exist below CO2 levels of approx 270ppmV. So, is my understanding incorrect or are readers ignoring the issue?
The vegetation threshhold established experimentally is about 150, not 270.
Thank you for the clarification.
Plants start dying in marginal areas, and deserts expand, long before CO2 gets down to 150.
C3 probably around 150, but C4 quite a bit lower. Now all vegetation appears to improve with higher CO2 levels. The point of diminishing returns? ???
They struggle @ur momisugly 280ppm, they barely survive @ur momisugly 180ppm and they go extinct @ur momisugly 150ppm
Apparently something changed my “AT” sign to something unintended. Soooo, no more “@”
That’s happened to me also. Don’t know what is causing it.
A good primer for those not familiar with continental drift earth history are the Scotese presentations on ytube. It’s hard to get your head around but there is no doubt this has happened in the past. Interesting future projection though. Earth history is fascinating.
Take a look at the drift reconstruction and the image below will then make sense. The absolute key to our climate now is the formation of the Antarctic circumpolar current as Rud pointed out above. While-ever this current keeps running, oceans will not boil, Antarctica will have continental ice and global surface temps will max out at 18-20 degC. The long term cooling trend shown on the image below is due to Antarctic ice and ocean cooling.
Thanks Jayrow.
At a lecture series I attended given by a retired physics professor, he presented a slideshow that showed how all the pieces of the current plates could be put back together.
And of course what these events over Earth’s ancient history had on oceanic dynamics.
Fascinating stuff.
Or visit the website of Scotese’s PaleoEarth Project — http://www.scotese.com which tries to summarize all the available fossil and geologic evidence of Earth’s past climates. There are two sets of maps there. One shows the probable location and orientation of landmasses for the past half billion or so years. The other shows best guesses as to the climates. There’s also a chart of past planetary temperature that shows pretty convincingly that the present state of the planet is unusually cold and that most of the past 500,000,000 years except a short period about 300,000,000 million years ago have been substantially warmer than the most recent 10,000,000 or so years.
Yes.
That’s it.
Things will be cold for as long as Antarctica is at the south pole, which is going to be quite a few million years still.
“Antarctica was once a lot warmer simply because it wasn’t then over the South Pole”
I’m curious – what was over the South Pole 33mya? How does anybody know? Maybe Antarctica was there, but below the sea, and just uplifted. Or maybe it was pretty much in its present position, but just turned on some interior axis? I hope nobody seriously thinks that they can work out an initial state of a present chaotic output, namely the fluid dynamics of plate tectonics!
As far as I know, even the poles were molten at one time. Now they aren’t, so they cooled. GHE enthusiasts cannot bring themselves to explain this simple fact, let alone accept it.
It doesn’t really matter – extracting CO2 from air doesn’t make it colder. Adding CO2 doesn’t make it hotter either. In that case, the GHE is about as real as phlogiston or caloric, don’t you think?
Climate Court mercy doesn’t extend to heretics.
Glad I didn’t say “Jehova”
Their own math and ideology vitiate this claim because most of the warm forcing THEY claim was already done over a BILLION years ago thus any additional increase will always be very very small since it has ALWAYS been above 150 ppm level in the air in those same billion years.
This is why I don’t give a dam what their “experts” say anymore because they have been LYING to us for years now.
“The galactic radiation intensity sets the baseline temperature from which all other drivers vary.”
Hardly. The “galactic radiation intensity” can’t even stop the Earth from cooling. It’s still a mostly glowing hot ball of rock, with a thin non-glowing skin.
“Snowball Earth” (or even “slushball” Earth is a figment of Carl Sagan’s imagination – he and his ilk imply (without actually saying so), that the Earth was created cold, and has heated up to its present temperature.
By magic, presumably, if you accept that the core is around 5000 K. No trouble to GHE believers – they imply (without actually saying so) that the ocean depths are warmed by sunlight which is somehow magnified by CO2! Nope – even subjecting a hot potato to full “galactic radiation intensity” won’t stop its interior from cooling, let alone make the interior hotter!
Sure, parts of the Earth’s surface can apparently warm up – glaciers come and go, droughts and floods occur, but this is to be expected in a chaotic system. Not predicted – just expected.
Overall, the Earth is cooling, as it must. On the surface, there are urban heat islands resulting in national heat islands, evidenced by a global heat island (GHI). Exterminate humanity by removing all CO2 from the atmosphere, and the “global temperature” will no doubt drop. Some alarmists would probably claim that the temperature drop was due to removal of CO2! Good thing this only occurs in GHE believers’ imagination.
I am not sure what the MYIC can teach that we don’t already know or don’t know.
It is generally thought (no proof possible) that the closing of the Panama Isthmus via plate tectonics about 3mya (separating the tropical Pacific and Atlantic) precipitated the Quaternary ice age starting about 2.6mya. Of course, correlation is not causation. And this correlation isn’t that correlated.
Proxies generally establish that the ~41ty glaciation cycle from 2.6mya on switched to ~120ty about 1mya. Nobody has a good reason why. Lots of unconvincing speculations—looked at them all over the past decade.
The MYIC will not adequately cover the ‘known’ Quaternary duration transition of interest. So after that great expense we will still dunno. Why bother—other than more useless dollars to climate researchers. JMHO.
Relevant to present day climate change, the last Glacial interlude, the Eemian, had a SLR highstand about 126tya. It ended about 118tya. Implied total duration < 20ky. The present Holocene interlude started (based on SLR) about 12kya. A similar duration means we are starting down into glaciation again. Yet the UNFCCC and IPCC are worried about CO2 ‘control knob’ warming by 2100. Perhaps we need to prescribe them near sighted reading glasses.
In the bigger picture, perhaps simply removing the Isthmus of Panama is the geoengineering solution to avoiding the inevitable upcoming ice age? Also solves the ‘China proxy control of Panama Canal’ problem newly identified. (Hopefully no snark sign needed.)
In a much smaller ‘big’ picture, we are told that the ‘climate science is settled’ yet much more money is needed to study it. We are told renewables are cheaper, but every grid with significant renewable penetration has much higher electricity costs. We are told EV’s are the future, when nobody is buying even with subsidies—for obvious range anxiety, cost, and liability reasons. At least in the US, climate alarm fantasy hit the 47 reality wall just a month ago. The result isn’t pretty.
Mr Istvan, you are a treasure!
A font of knowledge & wisdom even.
(a conundrum –
does knowledge & wisdom endow rationality on us, or does rationality endow us with knowledge & wisdom?)
So many questions, Grasshopper . . .
Yes, he is.
“We are told EV’s are the future, when nobody is buying even with subsidies—for obvious range anxiety, cost, and liability reasons.”
Oh dear. My future looks very dim. In my contrarian fashion, I purchased not only a gas (petrol) powered four wheel drive vehicle, but a Chinese one to boot! After a 15000 km trip, I’m quite content. All the bells and whistles I need, none that I don’t want (it doesn’t connect to the internet, if anybody is concerned that the Chinese Government can listen to me talking to my passengers), so the EV will have to wait.
I’m not even worrying about any potential ice age. It’s about 32 C, late afternoon. A couple of degrees cooler would suit me fine. Can’t see it happening any time soon. No climate crisis around here.
“At least in the US, climate alarm fantasy hit the 47 reality wall just a month ago. The result isn’t pretty.“
Oh, but the shock and awe are impressive to watch!
It seems that answers just lead to more questions, and political insanity leads to harsh realities. It is common that when a person stabs another they also cut themselves. The same may be true when science is used as a weapon rather than a careful tool.
A Klingon lament is to pity the warrior who slays all his foes. It may be a sad day when, if, we ever answer all the questions.
Rud, I’m late to the party here, so I don’t know if you or anyone else will read this. I’ve spent some time looking at glaciation over the last 800kyr. What I’ve found is that the timing of the interglacials can be explained using a simple three-cycle harmonic model. I think the sun is involved and have some ideas that I’m working on. One of the interesting things that I’ve found is that the 900-year cycle (which peaks in 2100) has been fading. I’ve posted a plot on X.
One of the biggest mistakes novices make is thinking that ice accumulation is caused by cold conditions. Ice accumulation is the result of snowfall overtaking snow melt. The snowfall is the dominant factor and depends on rising ocean temperature.
Snow starts its life as ocean water. It has to get into the atmosphere and that requires surface insolation on oceans. The rate of increase in atmospheric moisture iOS one of the most clearly evident climate trends over the past 40 years.
Go back last week and you will see daily snowfall records broken across northern Japan. Earlier in the boreal winter, Korea recorded record snowfall.
The attached shows the ocean SST anomaly for last week with the warm regions off Japan highlighted at almost 5C above the 30 year average.
The precession cycle dominates glaciation and recovery and the current NH ocean heating phase started 500 years ago. We are already observing the ocean SST response to the higher peak solar intensity that will continue to increase for 9,000 years.
Greenland already has glaciers advancing and the summit is already gaining altitude of 17mm/year.
?ssl=1
The SH is now in cooling phase but all land south of 60S remained glaciated. Greenland has only partially melted during the present interglacial.
Still no consideration of what effect, if any, that interplanetary dust might have on the climate of Earth.
What stands in the way of real discovery are obsessions, conceits and beliefs that human beings are somehow bigger than nature and can disturb balances simply by being where they are. This preoccupation with ourselves seems to forget or ignore the very premise that we are a product of all the very cycles that preceded the very thought of “us” and actually occurred without “our influence”..
Religion may once have been bad enough in standing in the way of human progress but it does at least have some depth. Our obsession with being intelligent, responsible and careful as we appear to be now could kill us much more effectively than any of the brave new world stuff that went before.
One day an intelligent species may laugh at our conceits of how an Earth without humans could not have developed instead of in the way it did develop. Are we not proof of how randomness is and does and shouldn’t we stop being so precious about ourselves and stop trying to big up our presence here? We do the best we can and change our minds as often as is necessary to get to where we want to get (or at least thought we wanted to get). History has some of the patterns we have discovered but what about all the stuff that stays hidden for reasons best unknown? Don’t all species survive or perish by taking risks and being adventurous and isn’t what we do now running counter to that?
OK, but why is what happened thousands of years ago relevant today, and if it is, so what?
Cheers,
Dr Bill Johnston
http://www.bomwatch.com.au
Bill,
But …, but …, but . . ..
How dare you challenge the consensus? Don’t you understand that “climate scientists” are the smartest people in the world, and use the past to predict the future?
On the other hand, like me (and the IPCC), you might believe that the atmosphere behaves chaotically, meaning that even though the present determines the future, the approximate present does not determine the approximate future.
Or maybe the aforesaid “climate scientists” are delusional, gullible, and exceptionally capable at fooling themselves.
The 100-kyr cycle doesn’t exist. The progressive cooling of the planet implied that it became progressively more difficult to get out of glaciations. So the 41-kyr cycle turned into a 82-kyr cycle. It returns to a 41-kyr one when eccentricity is high. Now high obliquity and high precession have to coincide in time for an interglacial to happen. But at the previous window they were misaligned, so the 82-kyr slipped into a 123-kyr (3 obliquity cycles) glaciation.
The 41-kyr interglacials are still taking place (numbers + asterisks), but some are cooler (asterisks) and we don’t identify them as interglacials. We are not just in an ice age, we are in a very severe one.
This statement shows you completely misunderstand what the precession cycle is.There is no “high” or “low” precession cycle. It just alters the time of the year when Earth is at perihelion and aphelion. This year perihelion occurred on 5th January and aphelion will occur on 4 July. Perihelion was on the 18 December in 1582 and jumped to 28 December in 1583. In 2500, perihelion will occur on 12 January.
The year-to-year variation in peak solar intensity at any latitude is primarily caused by the precession cycle. At the present time the peak intensity difference between the hemispheres is 80W/m^2. With SH summer solstice getting more sunlight than NH summer solstice. The difference is a function of the eccentricity so the 80W/m^2 could be in excess of 100W/m^2 at high eccentricity or as low as 60W/m^2 when orbital eccentricity is low.
Obliquity only makes small differences to insolation at high latitudes.
The recent era of glaciation cycles are multiples of the precession cycle. Obliquity has a small influence on the initiation of glaciation. The present obliquity is sufficient to enable glaciation as the NH oceans warm up.
Interglacials occur when the glacier calving cools the oceans. There is currently a 1 trillion tonne glacier cooling the southern ocean. Glacier calving at the peak of NH glaciation is much more severe than this baby. There are glacier scrapings observed at depths of 700m in the North Atlantic.
“Interglacials occur when the glacier calving cools the oceans.”
I don’t believe so. The oceans are heated from below, in case you didn’t know. It is a matter of observation that all icebergs, regardless of size eventually melt.
No chance of even a “slushball Earth”. Carl Sagan was dreaming – off with the fairies.
The climate changes because Earth’s energy balance changes, whether by change in the incident energy or the rate energy is lost from within the atmospheric and terrestrial system of energy loss to space, the feedbacks that maintain the equilibrium
The temperature within the system is changed by any radiative imbalance to dynamically rebalance the system at whatever temperature is naturally required – hence the climate is what that level of energy within the atmosphere and oceans will drive. The negative cooling feedbacks from radiation and evaporation of absorbed solar energy dominate the balance, and in particular the various processes evaporated water goes through after leaving the ocean surface before returning as precipitation to the ocean, w/o its latent heat, including becoming clouds, being returned back to water vapour by absorbing more solar energy, all of which latent heat is finally returned to space from the atmosphere, etc., That help?
I doubt going back another 200Ka on 800Ka of EPICA Dome C and Vostok will do more than keep a few academics well away from real work at Ozzie taxpayers expense for a few years.
Just because I can, I’ll point out that these records already show a massive lag in CO2 change relative to temperature, so CO2 cannot be causal of warming, also that it was lot warmer than now when CO2 was down to 2/3 what it is now, so CO2 has never been the dominant control of climate change, it lags temperature change and appears to have the effect of reducing the temperature of interglacials on this timescale. See Vostok mark up:
https://www.dropbox.com/scl/fi/d5p0fqh9vmqgkam1wvtig/Part-2-Vostok-with-mark-up-by-PB.mp4?rlkey=wkvzblsefwenmohmfpl56tpv3&dl=0
THis logic is also supported by the Holocene optimum, hotter by 2 deg K when the CO2 levels were 2/3 today’s, as Prof Stefenssen explains,:
https://vimeo.com/manage/videos/607494244
WE don’t need any more data to prove CO2 has never been a dominant control of climate change, or more than a small internal system perturbation for at least the 2.8Ma series of ice age cycles. Were there even extended ice sheets on land during the 41Ka series? It only cooled about half as much as the 100Ka cycles, with the same limiting temperature for the short warm periods. BUT, whateveritis, CO2’s effect is effectively noise level in the strongly controlled and continuously changing energy balance of the earth – that determines its GMST.
1.6W/m^2 since 1850 is nowhere near enough imbalance to create 1.5 deg K of warming when the natural negative feedback from all causes is c.10W/m2 per deg K. Something else does that. The same something that is there in the geological records which are conveniently denied by the IPCC, to falsely attribute all change for the last 2Ka to their chosen CO2 cause, hence the need for the hokey stick religion.
So what is causing that energy changing imbalance?
It seems that the limiting condition of a “real” interglacial is tropical oceans reaching 30C/303K, when rising energy being absorbed in the tropics cannot easily be lost by evaporation and radiation, so instead starts to seriously transfer to the poles to cool the tropics.
Story tip?
What is clear is what a fine line exists the glacial and interglacial between the convolved insolation effects of the MIlankovitch cycles on the earths very asymmetric absorbing surface, the Oceans that have almost twice the volume in the SH as in the NH, hold 2 years of solar enrgy in the top 200metres and provide most of the evaporative and directly radiated LWIR negative feedback by heat loss to space.
THIS IS MY THEORY……The only combination that delivers the full interglacial seems to require an ice cap to form on land, reduce sea levels by over 100metres whilst the 100Ka eccentricity maximum needs to combine with a 23Ka precessional maximum so the NH is closest to the Sun at perihelion.
So the lower thermal capacity (1/2) NH, that is 2x more dynamically sensitive to radiative change of +/- 40W/m2 over a year at max eccentricity, gets as close to the Sun as it ever can in the Summer……….. and the ice melts. In 7Ka flat.
Obviously the increase in land area as the continental shelf is exposed in the NH also increases the relative sensitivity of the NH to this most extreme insolation change. = More warming in degrees per W/m2 terms.
But doesn’t this cancel out over a year, as many suggest? The energy input does, but the asymmetric response of the polar ice in the NH means more of the extra enrgy is absorbed in the summer thawing than is due to the extra cold caused by reduced incident radiation.
… the summer extreme will melt more ice in the NH, while the winter NH extreme will have the same or less precipitation/snowfall rate in the extreme cold of an ice desert with the NH the furthest it ever gets from the Sun. The SH is covered in oceans so relatively untroubled by the same radiative imbalance.
On the other hand, it might be that a ball of really hot rock surrounded by water and gas is cooling quite slowly. The nearest external relevant heat source is the Sun – far, far away.
All of it is part of a fully deterministic chaotic system. Completely unpredictable. Your assumptions about the future are as good as anybody else’s.
The second graph is very informative. I generally get red flags before my eye when I see this kind of sine wave vs gray bars BS.
The reader is invited to see that it often lines up, subliminally “not notice” when it does not and fall for a suggested, false, conclusion of some correlation, then again falsely assumed to show causation.
we have we developed mathematical method to prevent us seeing faces in the clouds. We can calculate correlation coefficients and determine what percentage of the observed variations metched by the proposed variable. Causation is a whole other story.
What I can see by eye is in phase in the current period , OUT OF PHASE around -400ka and then back in phase further back.
That is pretty sure indication of near ZERO long term correlation.
More red flags than CCP , more BS than Trump’s $350BN sent to Ukraine.
Have all factors been considered? The solar system encounters higher gamma ray radiation in some parts of its journey around the center of the galaxy. The length of a day was shorter in the past…..the moon’s orbit and hence tides were different in the past. The energy output of the sun is a rock solid constant? Volcanoes and asteroid hits don’t follow a timetable.
I note that the chart “Glacial-Interglacial cycles during the Pleistocene” is not the chart by Liesecki and Raymo that has been used a lot to show the cycles. Liesecki and Raymo adjusted their data in order to make it correlate better with obliquity, which weakened the obliquity argument somewhat. I hope this chart is unbiased.
There is a problem with this statement in the above text.
“Continuing on to the confluence of high obliquity, high eccentricity where precession produces a series of significantly hotter northern hemisphere summers when the Earth is near its closest distance to the sun (apogee).”
During the Northern Hemisphere summer, the earth is at its farthest distance from the sun. Perhaps this needs to be corrected in the text so as to not confuse readers.
The most common interglacial interval of the last million years is 84600 years, just over two obliquity cycles, and a couple of shorter ones at 31000 years. Obliquity cycles reach parity with interglacials at 9 obliquity cycles, at 369 kyr.
Where there is an interglacial at a peak in obliquity, there was also be an interglacial 9 obliquity cycles later. Where there is no interglacial at a peak in obliquity, there will also be no interglacial 9 obliquity cycles later.
Note the mirror image symmetry around MIS11, which breaks down after the Eemian.
“As eccentricity and obliquity just begin to fall, we see temperature “jumps” (D-O events) in closely packed time regions. These hot blips are probably solar activity driven warm-ups.”
The interglacials should be solar driven warmups too, as there were several peaks in obliquity through the last 800 kyr which had no warming whatsoever. An interglacial could be regarded as a much stronger and longer lasting D-O event.
The intervals of D-O events should be in multiples of the same 863 year cycle which ordered alternating series of grand solar minima and high solar periods through the Holocene. Every fourth one shows up stronger in the GISP2 ice core series of the last 10 kyr..
The 863 cycle is ordered by Earth, Venus, Jupiter, and Uranus, That will be modulated Saturn and Neptune over extremely long periods. All four gas giants lined up in fairly tight inferior heliocentric conjunction in 3322 BC and in 1306 AD. But this cycle of all four gas giants has a slow slip, so a series of all four lining up well would take tens of thousands of years to return.
One should expect that specific planet cycles which force Earth’s orbital variations will meet up with planet cycles ordering solar variability over very long periods.