Guest essay by Dr. John A. Parmentola
The standard discussion of orbital climate forcing usually focuses on small changes in globally averaged annual insolation. But this perspective may obscure an important physical effect arising from orbital geometry itself.
The first key fact is that the Earth’s globally averaged annual insolation changes very little over epochal timescales. This occurs because the semimajor axis of the Earth’s orbit remains nearly constant — a conserved quantity of the two-body problem. The total annual solar energy entering the Earth system, therefore, remains approximately constant even as precession and obliquity evolve.
The second key fact is that the Arctic zone exhibits a very strong seasonal asymmetry. When the orbital year is divided into two half-year energy channels, the Arctic-zone second-half-year insolation (roughly late summer-autumn–winter) minus the first-half-year insolation (roughly late winter- spring–summer) is persistently large and negative over epochal timescales.
These two facts immediately imply an important physical consequence. If the Earth’s globally averaged annual insolation remains nearly conserved while the Arctic zone develops a large negative seasonal asymmetry, then a compensating positive asymmetry must exist elsewhere in the climate system because the globally averaged annual insolation remains nearly conserved. That compensating asymmetry occurs primarily in the tropical zone — because that is where the heat is.
This effect is what I call the Countervailing Obliquity–Precession Effect (COPE). COPE describes asymmetric orbital half-year insolation and energy channels arising from the coupled effects of precession and obliquity. The tropical and Arctic zones respond very differently because they are fundamentally different material environments.
In the Arctic zone, the climate response is dominated by melt-threshold suppression, snow accumulation, and seasonal refrigeration. In the tropical zone, the response is dominated by long-term energy accumulation over the oceans, evaporation, latent heat storage, and atmospheric moisture transport. Thus, COPE produces countervailing thermodynamic tendencies: – Arctic cooling and melt suppression, – coupled to tropical energy accumulation and latent heat production.
The effect also appears measurable in the current climate system. Using CERES satellite observations analyzed within the same orbital half-year framework, the tropical-zone asymmetry appears measurable in the present climate system. The analysis suggests that, on average annually, approximately 1 W/m² of the asymmetric forcing survived reflection and outgoing longwave radiation and entered the tropical-zone climate system over roughly the past two decades. This retained energy must then be partitioned among ocean heat storage, evaporation, atmospheric transport, clouds, and high-latitude processes.
COPE therefore potentially connects: – orbital geometry, – hydrological transport, – latent heat export, – Arctic cooling, – sea-level evolution, – and glacial–interglacial climate transitions through a persistent orbital-geometric asymmetry that appears measurable today.
The broader implication is that orbital forcing may influence climate far more through structured seasonal and latitudinal energy distribution than through comparatively small changes in globally averaged annual insolation alone.
Two sets of figures illustrate the effect clearly:
The above graph shows the two asymmetrical half-year energy accumulation channels, EH1 and EH2, at the top of the atmosphere (TOA) in the tropical zone (TZ), measured relative to a minimum that occurred about 4,600 years ago. Over most of the current epoch, the second-half channel, EH2, exceeds the first, EH1, producing the observed asymmetry until 1,000 years from now, when it will be zero and then shift to EH1 dominance. The energy deposition per 100 years associated with EH1 will linearly double at the TOA in the TZ over 3,000 years.
The graph above shows the two Arctic-zone (AZ) asymmetric insolation melt suppression channels, C1 and C2. The melt-suppression effect is best characterized by changes in C1 and C2 going forward, indicating a continued decline in C1 (summer-season) insolation and a slight increase in C2 (winter-season) insolation. C1 will decrease by about 5 W/m2 in about 4,000 years.
Together, these graphs reveal a coupled orbital-climate structure that may represent part of the missing thermodynamic linkage between orbital forcing and glacial–interglacial evolution. In this way, COPE could help link orbital geometry to hydrological transport, latent heat export, and sea-level changes while supplementing traditional Milankovitch theoretical explanations.
One unusual aspect of COPE is that it potentially connects orbital-climate phenomena across past, present, and future climate evolution through a persistent orbital-geometric asymmetry that is currently measurable.
Further details of this effect and its potential consequences can be found here: https://doi.org/10.5281/zenodo.19825774
The elliptical orbit, tilted axis and albedo drive the terrestrial systems by orders of magnitude compared to GHGs.
It amazes me that so many people, (not you Nicholas), chase some meaning in one or two extra or lesser W/m2, spread out over a season or two and try to allocate ice ages or deserts to the result. When a more significant effect is observed using just albedo.
If you doubt my logic, then walk bare foot on a piece of white metal that’s been in the sun all day and then walk on a black piece.
Albedo rules the heat. Now that I’ve announced it, do I get a grant to paint the ocean surface white, (if you want cooling), or black if you are off on a summer holiday.
Grant money can be delivered in large brown paper bags and no I don’t provide receipts.
Albedo is one of those repurposed words.
Emissivity and permittivity apply to anything involving EM fields and waves.
Bond albedo versus geometric albedo are too often conflated by Trans-Reality Alarmists.
In the infrared, the oceans are already black with an emissivity of over 0.98. I guess the wind could “paint them white” but in IR they remain black. I don’t see much future in painting oceans, but there is money in painting seascapes. You can sell those in brown paper bags too.
GHG is a bogus concept used by the Trans-Reality Activists.
We need to stop using their lexicon. Using their vocabulary and definitions only serves to give them credibility where none is deserved.
“the Arctic zone (AZ) response is governed not by cumulative energy but by melt-season insolation trends reflecting the temperature threshold required for ice melt.”
I can support the idea of cumulative energy derived from the COPE mechanism over time, so perhaps some of the OHC increase since 1979 can be ascribed to more melt-season insolation, but I can provide evidence where cumulative energy in the ocean is the main cause of Arctic ice melt. CERES TOA solar data shows 75°N with a slight 1% per annual downtrend since 2000, so I’m not sure what role orbital changes play during this short trend, whether it’s the main influence.
The North Atlantic ocean heat content has actually measured significant energy accumulation during the instrumental era since 1979 that can be tied to both ice melt and solar activity levels.
Here the NA OHC accumulated during solar cycles exceeding the decadal warming threshold.
That is all fascinating, but everyone wants to know when the next ice-free Arctic day will happen.
Hopefully the author’s data and code will become available after publication, with a prediction.
Earth’s axis has been trending towards less tilt for a long time and will continue to do so for a very long time to come. Thus the climate is slowly becoming more moderate, slightly warmer overall.
But at a very very slow pace.
If the 11-year solar maximum and minimum cycle affects the Earth’s temperature, why doesn’t the Earth’s temperature vary with solar maximum and solar minimum?
Was that a circular-type question? Here are the basic concepts as I see them.
Solar cycles do affect the Earth’s temperature, causing it to vary from solar min to max, and from the solar max to min.
The eastern tropical Niño regions are greatly and predictably influenced by solar cycles, and there is net ocean heat accumulation after solar activity is high enough, ie, SN>95.
Global SST step-changes follow after these solar-induced tropical step changes.
Note: the 1361.25 W/m2 TSI decadal warming threshold is equal to 95 sunspot number.
These tropical temperature changes induce albedo changes which in turn controls the amount of absorbed solar radiation in the ocean, leading to decadal warming steps during solar maximum periods. Orbitally-induced changes are much slower and less impactful in the short term. In a nutshell this is how the sun’s cycles have caused global warming, much more than orbital changes did since the Little Ice Age.
The Little Ice Age came about mostly due to the very long duration(s) under the 95 SN decadal ocean warming threshold before and during the Maunder Minimum.
I searched about the impact of solar cycles on Earth’s temperature and got the following answer:
“This translates to a global temperature effect of around 0.1°C or less peak-to-trough.”
That is the usual answer when solar-induced albedo changes aren’t included.
My work on this isn’t published yet except in several posters so your searches won’t pick up this TSI force multiplier effect in others’ papers.
I asked Grok to compare daily TSI at Earth distance with Earth’s daily temperature, period 1979-today.
Grok made a graph comparing daily TSI at 1AU and Earth’s average temperature.
And 2 more graphs with monthly average comparison and a smoothed daily comparison:
Interesting data.
One problem. Earth does not have a global average temperature.
Average was a typo on my part. It should be anomaly.
Grok used ERA5-based 2m air temperature anomaly (relative to 1991–2020 baseline).
The reference period 1991–2020 is a standard that can be converted to 1850-1900 Preindustrial.
I am unsure if Grok uses realistic data for the graphs it creates?
I know you are being forthright. No disrespect intended.
But anomalies are not valid when averaged over a global temperature set.
Whether anomaly or temperature, the Sahara at +30C and Antarctic at -30C does not equate to an average of 0C.
Deltas in one part of the world are independent, mostly, of deltas on the other side of the planet. It really is not so simple. What causes the Sahara to go from +30C to +31C and Antarctica from -30C to -28C are not due to the same cause.
The whole Earth and parts of the Earth are different things.
It is not enough to look at parts of the Earth:
You also have to look at parts of the Earth during different periods of the year to find the causes of temperature changes.
The asymmetry is driven by the great difference in the amount and distribution of land VS water surface area in the northern and southern hemispheres, and how summers and winters happen near aphelion and perihelion.
The north has more land but none at and around the pole. The south has more water but nearly all the area within the bounds of the current latitude of the antarctic circle is filled with land.
So arctic winters are moderated by the influx of some heat by ocean currents all the way to the pole VS antarctic winters only getting heat input from atmosphere convection. That’s why there’s all those records for coldest observed temperature in antarctica.
And yet again I shall pose this question. How much area lies within the theoretical minimum and maximum latitudes of the antarctic and arctic circles? How different would you calculate the overall climate may be when the axis reaches minimum or maximum tilt, and at what points in the orbit will the seasons occur at the time of minimum and maximum tilt?
I say theoretical because there’s no recorded observations of the minimum or maximum latitudes. There are theories based on observed changes in the axial tilt, geomagnetic measurements of solidified igneous rocks, and other things that appear to correlate with tilt changes, but until someone is here on Earth several thousand years in the future to actually observe the axis reach a minimum tilt then turn and start shifting towards more tilt, we absolutely do not know what the minimum can be. Then it will be an even longer amount of time before an observation of the maximum tilt can happen. Actual observation of a thing is always better than calculated guesswork.
The axial precession is a different can of math. Since it goes around one way and has a steady, directly measurable speed, it can be fairly precisely calculated when and where the poles were aimed *that direction*. The tilt angle slowly wobbles back and forth, though currently the wobbles are going more towards less tilt.
“The north has more land but none at and around the pole. The south has more water but nearly all the area within the bounds of the current latitude of the antarctic circle is filled with land.”
Yes, also, what did the Northern Hemisphere coastlines look like for the first thousand years or so after the ice had more or less melted, before isostatic rebound? What will the coastlines (and ocean circulation) look like after a few thousand years from now? That will have at least as much effect on the Arctic/subarctic weather and climate as would measly insolation changes from gradual orbital shifts.
Spot on.
Part of your several thousand years will include alterations of the earth and moon orbits around the sun and the solar orbit around the barycenter.
The minimum perihelion distance for each century changes.
Is there a relationship between the minimum perihelion distance for each century and the Earth’s temperature?
Milankovitch agrees.
do you have a reference to the equations determining those variations in eccentricity ?
I found the Perihelion data on the astropixel.com page.
The page states where the data comes from:
Acknowledgment
All calculations are by Fred Espenak, and he assumes full responsibility for their accuracy. Algorithms used in predicting the Planetary Ephemeris Data are based on Astronomical Algorithms by Jean Meeus (Willmann-Bell, Inc., Richmond, 1998).
http://www.willbell.com/math/mc1.HTM
The maximum perihelion distance for each century changes.
Is there a relationship between the maximum perihelion distance for each century and the temperature of the Earth?
Thus we are exiting, slowly, the inter-glacial optimum.
“The total annual solar energy entering the Earth system, therefore, remains approximately constant even as precession and obliquity evolve.” Only if the energy output of the Sun is constant. It isn’t. See Nicola Scafetta for some interesting information on that subject.
Spot on.
There likely are a number of factors affecting climate, and this may be one. How important it is remains to be seen. My guess is that it is changes in the sun through Bond cycles or the Svensmark effect which, over time are the most powerful, with the oceans factoring in as well. Somewhere, way down the list of factors is CO2, playing its small bit part, perhaps more along the lines of helping to keep climate stable rather than, as the climate caterwaulers would have us believe, destabilizing climate.
Agreed.
Too repurpose the Clinton campaign slogan:
“It’s the sun, stupid!”
It’s the cloud cover actually…
It’s both.
My core interest is implementing a personal computing environment in which I can succinctly , executably express ( array ) math , generalized & simplified from APL . See CoSy.com/y26/NL202603.html .
I just start with the most essential computation : the radiative equilibrium of a gray ( flat spectrum ) ball in our orbit . It is too little appreciated that a radiantly heated gray body , however dark or light , comes to the same temperature as a black . That’s about 278.7 +- 2.3 from perihelion , January 3 this year , to aphelion .July 6 . So our bottom of atmosphere temperature is ~ 10K warmer than the gray body equilibrium due to the adiabatic tradeoff of gravitational , potential , and thermal , kinetic + radiant , energy keeping total energy density constant as required by Conservation of Energy , and extending to the core of the planet .
I have never seen a computation of our radiative equilibrium based on an asserted measured Schwarzschild ( color ) spectrum of the Earth from space . If someone points me to a table , I’ll return the calculation of the implied equilibrium .
And this is the point at which classical quantitative analysis of our planetary temperature ends and becomes statements of more or less .
I would also be interested in calculating just how extreme our ` color would have to be to produce an equilibrium of the endlessly parroted 255K value based on the falsehood that a gray ball comes to a lower equilibrium than a black .
Only when these essentials are understood do I see much point in getting into calculations of a pixel map of our spectrum as seen from outside , or its diurnal variation . Or going further to a voxel model of the vertical structure of the atmosphere .
In an array language , the code still remains at the level of succinct expression of the physics , but the computation required increases as at least the 4th power of the resolution .
It is interesting that the North-South asymmetry between land and ocean apparently nearly eliminates in our measured bottom of atmosphere temperatures that annual 4.6K variation in our radiative equilibrium.