I’m putting up a copy of a comment from WUWT by Salvatore Del Prete.
Why? Because it is interesting, and I keep forgetting where he’s posted things, so figure this will make it easier to find again ;-)
He posted in last then first order in two parts and I’m leaving it that way.
First, there was this ‘teaser’:
Salvatore Del Prete May 29, 2015 at 11:10 am
I would say before this decade ends because what is GOING to happen is the global temperature trend is going to be in a definitive down turn due to prolonged minimum solar conditions and the associated secondary effects.
The PDO/AMO and ENSO will also be more often then not in a phase which promotes global cooling. Evidence exist for a connection between these indices and solar/lunar parameters.
Then a bit further down, the full description:
Salvatore Del Prete May 29, 2015 at 11:14 am
Here is why and how I think the climate may change. Part two is sent first followed by part 1.
HOW THE CLIMATE MAY CHANGE
Below I list my low average solar parameters criteria which I think will result in secondary effects being exerted upon the climatic system.
My biggest hurdle I think is not if these low average solar parameters would exert an influence upon the climate but rather will they be reached and if reached for how long a period of time?
I think each of the items I list , both primary and secondary effects due to solar variability if reached are more then enough to bring the global temperatures down by at least .5c in the coming years.
Even a .15 % decrease from just solar irradiance alone is going to bring the average global temperature down by .2c or so all other things being equal. That is 40% of the .5c drop I think can be attained. Never mind the contribution from everything else that is mentioned.
What I am going to do is look into research on sun like stars to try to get some sort of a gage as to how much possible variation might be inherent with the total solar irradiance of the sun. That said we know EUV light varies by much greater amounts, and within the spectrum of total solar irradiance some of it is in anti phase which mask total variability within the spectrum. It makes the total irradiance variation seem less then it is.
I also think the .1% variation that is so acceptable for TSI is on flimsy ground in that measurements for this item are not consistent and the history of measuring this item with instrumentation is just to short to draw these conclusions not to mention I know some sun like stars (which I am going to look into more) have much greater variability of .1%.
I think Milankovich Cycles, the Initial State of the Climate or Mean State of the Climate , State of Earth’s Magnetic Field set the background for long run climate change and how effective given solar variability will be when it changes when combined with those items. Nevertheless I think solar variability within itself will always be able to exert some kind of an influence on the climate regardless if , and that is my hurdle IF the solar variability is great enough in magnitude and duration of time. Sometimes solar variability acting in concert with factors setting the long term climatic trend while at other times acting in opposition.
Solar Flux avg. sub 90
Solar Wind avg. sub 350 km/sec
AP index avg. sub 5.0
Cosmic ray counts north of 6500 counts per minute
Total Solar Irradiance off .15% or more
EUV light average 0-105 nm sub 100 units (or off 100% or more) and longer UV light emissions around 300 nm off by several percent.
IMF around 4.0 nt or lower.
The above solar parameter averages following several years of sub solar activity in general which commenced in year 2005..
If , these average solar parameters are the rule going forward for the remainder of this decade expect global average temperatures to fall by -.5C, with the largest global temperature declines occurring over the high latitudes of N.H. land areas.
The decline in temperatures should begin to take place within six months after the ending of the maximum of solar cycle 24.
Secondary Effects With Prolonged Minimum Solar Activity. A Brief Overview.
A Greater Meridional Atmospheric Circulation- due to less UV Light Lower Ozone in Lower Stratosphere.
Increase In Low Clouds- due to an increase in Galactic Cosmic Rays.
Greater Snow-Ice Cover- associated with a Meridional Atmospheric Circulation/an Increase In Clouds.
Greater Snow-Ice Cover probably resulting over time to a more Zonal Atmospheric Circulation. This Circulation increasing
the Aridity over the Ice Sheets eventually. Dust probably increasing into the atmosphere over time.
Increase in Volcanic Activity – Since 1600 AD, data shows 85 % approximately of all major Volcanic eruptions have been associated with Prolonged Solar Minimum Conditions. Data from the Space and Science Center headed by Dr. Casey.
Volcanic Activity -acting as a cooling agent for the climate,(SO2) and enhancing Aerosols possibly aiding in greater Cloud formation.
Decrease In Ocean Heat Content/Sea Surface Temperature -due to a decline in Visible Light and Near UV light.
This in turn should diminish the Greenhouse Gas Effect over time, while promoting a slow drying out of the atmosphere over time. This may be part of the reason why Aridity is very common with glacial periods.
In addition sea surface temperature distribution changes should come about ,which probably results in different oceanic current patterns.
The constant mistake in this field is trying to link a one cause and effect to the climate and thus a climatic outcome. It does not work that way . The climate is very complex and has to be looked at from all perspectives to see what may or may not occur with the climate.
This is the approach I have taken trying to tie all of the items that may effect the climate to one another in a process that when they phase, if the phase and degree of magnitude change and duration of time is sufficient enough the climate will gradually change until brought to a threshold at which point in time the climate will change abruptly due to a cascade effect of all these items that exert an influence on the climate phasing .
I also try to show the regulators of the climate on a very large scale those being Milankovich Cycles, the Initial State of the Climate or Mean State of the Climate , State of Earth’s Magnetic Field which set the background for long run climate change and how effective given solar variability will be when it changes when combined with those items, and the secondary effects associated with this solar variability which give the phasing I am talking about in the above paragraph. Nevertheless I think solar variability within itself will always be able to exert some kind of an influence on the climate, but how much will depend on the solar variability itself and where the regulators of the climate are at in the very large scale picture.
The approach often taken and this article is no exception is to simplistic in that it(they are ) is looking for a one cause /effect thus climate outcome as if all of what they mention is somehow in isolation and it does NOT work that way.
This is why I do not take these kind of articles seriously because they offer but one piece of the larger climate puzzle.
Here is what I have concluded. My explanation as to how the climate may change conforms to the historical climatic data record which has led me to this type of an explanation. It does not try to make the historical climatic record conform to my explanation. It is in two parts.
HOW THE CLIMATE MAY CHANGE
Below are my thoughts about how the climatic system may work. It starts with interesting observations made by Don Easterbrook. I then reply and ask some intriguing questions at the end which I hope might generate some feedback responses. I then conclude with my own thoughts to the questions I pose.
From Don Easterbrook – Aside from the statistical analyses, there are very serious problems with the Milankovitch theory. For example, (1) as John Mercer pointed out decades ago, the synchronicity of glaciations in both hemispheres is ‘’a fly in the Malankovitch soup,’ (2) glaciations typically end very abruptly, not slowly, (3) the Dansgaard-Oeschger events are so abrupt that they could not possibility be caused by Milankovitch changes (this is why the YD is so significant), and (4) since the magnitude of the Younger Dryas changes were from full non-glacial to full glacial temperatures for 1000+ years and back to full non-glacial temperatures (20+ degrees in a century), it is clear that something other than Milankovitch cycles can cause full Pleistocene glaciations. Until we more clearly understand abrupt climate changes that are simultaneous in both hemispheres we will not understand the cause of glaciations and climate changes.
. My explanation:
I agree that the data does give rise to the questions/thoughts Don Easterbrook, presents in the above. That data in turn leads me to believe along with the questions I pose at the end of this article, that a climatic variable force which changes often which is superimposed upon the climate trend has to be at play in the changing climatic scheme of things. The most likely candidate for that climatic variable force that comes to mind is solar variability (because I can think of no other force that can change or reverse in a different trend often enough, and quick enough to account for the historical climatic record) and the primary and secondary effects associated with this solar variability which I feel are a significant player in glacial/inter-glacial cycles, counter climatic trends when taken into consideration with these factors which are , land/ocean arrangements , mean land elevation ,mean magnetic field strength of the earth(magnetic excursions), the mean state of the climate (average global temperature gradient equator to pole), the initial state of the earth’s climate(how close to interglacial-glacial threshold condition it is/ average global temperature) the state of random terrestrial(violent volcanic eruption, or a random atmospheric circulation/oceanic pattern that feeds upon itself possibly) /extra terrestrial events (super-nova in vicinity of earth or a random impact) along with Milankovitch Cycles.
What I think happens is land /ocean arrangements, mean land elevation, mean magnetic field strength of the earth, the mean state of the climate, the initial state of the climate, and Milankovitch Cycles, keep the climate of the earth moving in a general trend toward either cooling or warming on a very loose cyclic or semi cyclic beat but get consistently interrupted by solar variability and the associated primary and secondary effects associated with this solar variability, and on occasion from random terrestrial/extra terrestrial events, which brings about at times counter trends in the climate of the earth within the overall trend. While at other times when the factors I have mentioned setting the gradual background for the climate trend for either cooling or warming, those being land/ocean arrangements, mean land elevation, mean state of the climate, initial state of the climate, Milankovitch Cycles , then drive the climate of the earth gradually into a cooler/warmer trend(unless interrupted by a random terrestrial or extra terrestrial event in which case it would drive the climate to a different state much more rapidly even if the climate initially was far from the glacial /inter-glacial threshold, or whatever general trend it may have been in ) UNTIL it is near that inter- glacial/glacial threshold or climate intersection at which time allows any solar variability and the associated secondary effects no matter how SLIGHT at that point to be enough to not only promote a counter trend to the climate, but cascade the climate into an abrupt climatic change. The back ground for the abrupt climatic change being in the making all along until the threshold glacial/inter-glacial intersection for the climate is reached ,which then gives rise to the abrupt climatic changes that occur and possibly feed upon themselves while the climate is around that glacial/inter-glacial threshold resulting in dramatic semi cyclic constant swings in the climate from glacial to inter-glacial while factors allow such an occurrence to take place.
The climatic back ground factors (those factors being previously mentioned) driving the climate gradually toward or away from the climate intersection or threshold of glacial versus interglacial, however when the climate is at the intersection the climate gets wild and abrupt, while once away from that intersection the climate is more stable. Although random terrestrial events and extra terrestrial events could be involved some times to account for some of the dramatic swings in the climatic history of the earth( perhaps to the tune of 10% ) at any time , while solar variability and the associated secondary effects are superimposed upon the otherwise gradual climatic trend, resulting in counter climatic trends, no matter where the initial state of the climate is although the further from the glacial/inter-glacial threshold the climate is the less dramatic the overall climatic change should be, all other items being equal.
The climate is chaotic, random, and non linear, but in addition it is never in the same mean state or initial state which gives rise to given forcing to the climatic system always resulting in a different climatic out-come although the semi cyclic nature of the climate can still be derived to a degree amongst all the noise and counter trends within the main trend.
Why is it when ever the climate changes the climate does not stray indefinitely from it’s mean in either a positive or negative direction? Why or rather what ALWAYS brings the climate back toward it’s mean value ? Why does the climate never go in the same direction once it heads in that direction?
Along those lines ,why is it that when the ice sheets expand the higher albedo /lower temperature more ice expansion positive feedback cycle does not keep going on once it is set into motion? What causes it not only to stop but reverse?
Vice Versa why is it when the Paleocene – Eocene Thermal Maximum once set into motion, that being an increase in CO2/higher temperature positive feedback cycle did not feed upon itself? Again it did not only stop but reversed?
My conclusion is the climate system is always in a general gradual trend toward a warmer or cooler climate in a semi cyclic fashion which at times brings the climate system toward thresholds which make it subject to dramatic change with the slightest change of force superimposed upon the general trend and applied to it. While at other times the climate is subject to randomness being brought about from terrestrial /extra terrestrial events which can set up a rapid counter trend within the general slow moving climatic trend.
Despite this ,if enough time goes by (much time) the same factors that drive the climate toward a general gradual warming trend or cooling trend will prevail bringing the climate away from glacial/inter-glacial threshold conditions it had once brought the climate toward ending abrupt climatic change periods eventually, or reversing over time dramatic climate changes from randomness.
This also gives an easy place for Salvatore to point a link if he doesn’t want to paste the whole thing in somewhere.
At WUWT, the discussion following it has Leif Svalgaard saying “not happening” as he points to TSI (which is what he usually does with this kind of ‘sun quiet making things colder’ discussion).
If Salvatore would like any edits made, I’m happy to make them. Just put a comment below.
On the Milankovitch complaints, I find them weak; but they are really only a preamble to the rest. The points are valid exemplars of “something different happening” for some cases (D.O. events, Younger Dryas) but the first two I think miss some points, while the last two are non-Milancovitch.
1) Hemispheric synchronous timing of Ice Ages. Just not a problem. Milankovitch theory actually is the explanation for why. Since the S.Pole is always covered in ice (as it is a land mass so can not be melted from below via warm water), there is no interglacial when it is the warm pole. ONLY when the N. Pole is the warm pole is there enough heat to melt the ice and get things warm as an interglacial. Since a key part is played by warm water currents getting under the ice and melting it, once that ice is gone, the rest of the global water can warm up nicely and the whole place is warmer. And once the ice does not melt, stacking up a mile of ice changes the ocean currents so that the south gets colder too.
Key point is that the N. pole melts when it is pointed at the sun during summers AND the earth is furthest from the sun. There are more days of summer then, and it is the longer summer / shorter winter that starts the melt. In all other configurations, once you ice up, you stay ice. Pointing the Antarctic at the sun a bit longer just leaves it a pile of ice…
2) Rapid end of ice. Also not problematic. Once you get a warmer water north, you also get warm rain instead of snow. Rain rapidly melts ice, that raises sea level and starts a disruption cycle of ungrounding ice, with breakup and flushing from the frozen north. Something that just can’t happen in the South Pole. Return of ice is slower as that depends on evaporation / mass flow / snow fall and it just takes a long time to build up 10 miles of snow to make 1 mile of ice. Especially as the glacial periods are also very dry periods. Hot wet melts ice fast and flushes the arctic. Cold dry builds up snow slowly. Also add in that once the ocean is deep enough and currents reorganize you get the gulf stream pointed at the N. Polar ice and that really gets things melting faster. https://chiefio.wordpress.com/2014/05/04/arctic-flushing-and-interglacial-melt-pulses/
Salvatore then cited one of my postings as supporting his ideas:
which it does to some extent. It supports the notion of D.O. events being triggered by things non-Milankovitch. In particular, the switching of the Gulf Stream / Northern Drift and the effect on the ocean overturning currents.
which gets to
3) D.O. Events. Not a concern for Milankovitch theory at all. Just isn’t. It is a distinct and separate process with its own causes and timing. IMHO most likely caused by lunar tidal extremes as the lunar orbit shifts along with solar shifts. Now I’d expect that the same timing that causes D.O. Events (or Bond Events during interglacials like now) at about 1500 year periods would likely act as a trigger for the exact timing of onset / end of interglacials, but not causal (until things are ready to trigger). As of now, we are in the ‘metastable’ band of W/m^2 of insolation. Next Bond Event could well leave us in a glacial state, and stable in that glacial. IMHO we almost dropped into it during the Little Ice Age, but didn’t quite stick. Next down will be further and colder (as orbits have moved on a bit more).
Now predicting the exact date of the next Bond Event could be a bit hard. Some folks count the L.I.A. as the last one, but I think it was a Half Bond event. That would make Bond 1 the start of The Dark Ages in 540 AD and put the Bond Event Zero at 1470+540= 2010 AD or so “start” date. Just about the time the sun went quiet (or 2040 AD if you use a 1500 year pulse). Or right about now. Do realize that D.O. Events are warming often preceding a cold plunge. A related thing is the Heinrich Event that is similar but shows ice rafted debris when still in a cold phase. Bond Events catch the cold plunge after the warm, during interglacials. So one reasonable surmise is that the recent “warming” period from 1970 to now was just a D.O. event, before the Bond Event drop.
In the Northern Hemisphere, they take the form of rapid warming episodes, typically in a matter of decades, each followed by gradual cooling over a longer period. For example, about 11,500 years ago, averaged annual temperatures on the Greenland ice sheet warmed by around 8 °C over 40 years, in three steps of five years (see, Stewart, chapter 13), where a 5 °C change over 30–40 years is more common.
Heinrich events only occur in the cold spells immediately preceding D-O warmings, leading some to suggest that D-O cycles may cause the events, or at least constrain their timing.
The course of a D-O event sees a rapid warming of temperature, followed by a cool period lasting a few hundred years. This cold period sees an expansion of the polar front, with ice floating further south across the North Atlantic ocean.
Now a Heinrich Event is a load of ice rafted debris in the just preceding cold period before the D.O. Event. As these only happen during glacials, we would not see these now as there was little debris on the ice over the water. But I do need to point out that the L.I.A. end had a load of glacial ice drift in the N. Atlantic. Even sunk a famous ship… that lead to a Titanic Movie and buckets of money… So we HAVE had ice flowing out of the North Polar area, just not dirty ice, during a cold period, preceding a rapid warm up of 30 to 40 years, that has folks on the Warmers side claiming Greenland has warmed by 3 or 4 C. Sure sounds like the right pattern to me. That, then, ought to be followed by a cold plunge when the Bond Event cold part hits.
But none of this is related to Milankovitch, other than that the same 1470 / 1500 year “clock” runs in both but shows up as D.O. Events when things are frozen and as the other half cycle Bond Events of cold when things are warm. That clock, IMHO, is lunar tidal. The paper cited in that link:
Seems to attribute things to fresh water inflows, but ignores the giant tidal metronome. Still, I think their model of stability vs metastable is right, even if the driver is more lunar / tidal.
Once the system is in the `warm’ mode with convection in latitudes north of Iceland, it becomes insensitive to the applied, weak 1,500-year forcing cycle (this experiment was performed but is not detailed here). The freshwater budget of the Nordic Seas is then dominated by the vigorous circulation; anomalies in surface forcing cannot accumulate to create noticeable salinity anomalies as in the stratified `cold’ mode. For this reason, the Holocene climate in our model is stable with respect to the 1,500-year forcing cycle, while the glacial climate is not. We can thus explain the large fluctuations of Greenland temperature during the glacial climate in terms of ocean circulation instability, requiring only a weak trigger but not necessarily any major ice-sheet instability. In the Holocene, the 1,500-year cycle is still present but is not amplified by ocean circulation instability, so that its signature is only weak.
Note this is talking about the whole Holocene. As we are nearer the end than the middle, we are starting to enter the unstable mode range of insolation in summer. That is, summers are shorter than 5000 years ago in the N. Hemisphere. At some point the ice starts to stay during one of those “weak 1,500 year forcing cycle” events and we re-enter the cold mode. Then snow and ice build up for 100,000 years (though with a periodic 1500 year wiggle).
So the whole D.O thing is about a sub-cycle, not the full glacial / interglacial Milankovitch cycle.
Which brings us to:
4) Younger Dryas. I’m pretty sure it is an anomaly caused by a cometary or asteroid impact. Looking at other interglacials, they spike higher and warmer than we did. Ours got “peak clipped” by something, and that looks like it was the Y.D. that prevented the usual overshoot / plunge back. Overlay our curve on the older curve, we are just about to arrive at their down line, just with the peak flattened. At that point I expect us to rejoin the normal process of decline. I.e. much faster than we’ve had for the last 8,000 years.
http://cosmictusk.com/ covers the impact thesis and evidence in great depth and detail.
So one needs to set the Younger Dryas aside as a one-off type of event. Most likely… Unless it is part of a periodic debris field.
Which also links to a paper that looks at lunar tidal forces and finds them quite adequate to explain things.
Now I suspect their use of 1800 year cycles may have “issues”, but there is a potential they just missed a trick. Some folks have found a 1470 ish year cycle if you adjust for when seasons line up with the particular face pointing at the sun. I also postulate a similar thing when looking at the ’60 year’ cycle (that can be shorter at 50-something) as three lunar cycles that return to the same ocean facing the tidal pull every 3rd.
So one small problem folks have is that it is unclear if the 1470 is an artifact of averaging together 1200 and 1800 year events (as one ‘catches’ on a shorter stimulus cycle, or skips a short beat to the longer event – stochastic resonance and all) or if it is a result of some subtle alignment season things as astroclimateconnection postulates, or if it is just measurements that vary more but are being averaged for a precise number with false precision.
But in any of those cases, I think the Younger Dryas is “special” and has to be treated as such. It quite likely happened during the start of the swap of W/m^2 to ‘stable warm’ and likely with a load of crap in the air, so could easily have knocked things back to cold for 1000 years until the next 1500 year uptick kicked it again.
Note that none of this nit harvesting about what is, or is not, related to Milancovitch has any real effect on what Salvatore Del Prete is saying. He refers to Milankovitch only as preamble, and as a sort of lever to say “there’s more here that can change faster”. Which there is, and which it does. And, given our lower W/m^2 than needed to exit a glacial, the next time we start the ice over, it is likely to stay as we enter the unstable ocean oscillator phase. Yes, it is possible that the next Bond Event will be recoverable and that we end up with 1500 more years to Ice Down, but it is entirely a crap shoot. I really really do hope that CO2 is a “greenhouse gas” and I’m dead wrong. At least then we might have a way to avoid frozen. But everything I’ve seen so far looks much more like a “one and done” and the next Bond Event dumps us in Ice City.
With all that preamble / nit harvest out of the way, the rest of the actual thesis is basically that “the sun does it” with details. I would only add a pointer at the places and ways EUV and UV change drives things. UV enters the ocean to great depth (100 feet range) and deposits energy there. IR (that increases when UV drops, holding TSI near constant) causes prompt evaporation at the surface. UV causes very long cycle warming of the ocean. IR causes increased evaporative cooling and precipitation. In the thermosphere and stratosphere UV is absorbed, depositing heat.
Ozone and temperature
Within this layer, temperature increases as altitude increases (see temperature inversion); the top of the stratosphere has a temperature of about 270 K (−3°C or 26.6°F), just slightly below the freezing point of water. The stratosphere is layered in temperature because ozone (O3) here absorbs high energy UVB and UVC energy waves from the Sun and is broken down into atomic oxygen (O1D) and diatomic oxygen (O2) at wavelengths of below 1180 nm. Atomic oxygen is found prevalent in the upper stratosphere due to the bombardment of UV light and the destruction of both ozone and diatomic oxygen. The mid stratosphere has less UV light passing through it, O and O2 are able to combine, and is where the majority of natural ozone is produced. It is when these two forms of oxygen recombine to form ozone that they release the heat found in the stratosphere. The lower stratosphere receives very low amounts of UVC, thus atomic oxygen is not found here and ozone is not formed (with heat as the byproduct). This vertical stratification, with warmer layers above and cooler layers below, makes the stratosphere dynamically stable: there is no regular convection and associated turbulence in this part of the atmosphere. The top of the stratosphere is called the stratopause, above which the temperature decreases with height.
As that UV falls off, the atmospheric height shortens, and this was observed by NASA as lower drag on satellites (among other ways to observe it).
At this point, Stephen Wilde likes to jump in and tell me that the stratosphere gets hotter. http://www.newclimatemodel.com/new-climate-model/ We then have a ‘go around’ where I point out that descending air, especially near the poles in the night jet, will rise in temperature, and that I’m talking about energy deposition not local temperature excursions; and that I’m talking about the actual energy delivered not the ozone cycle further along the process releasing heat. I’m talking energy flux as ‘heat’ and he’s talking temperature. I also then point out we are likely talking about different parts of the stratosphere (ozone UV absorbing vs recombine ozone creation heat release). We’ll see if this disclaimer covers it this time ;-) But it’s pretty clear UV and UV delivered energy falls off in a solar funk, and I don’t know what to call stratosphere with less energy in it than ‘less warm’ or ‘cooling’. At any rate, by the time all this is done, we end up with cold air flowing out of the polar regions and the jet stream going ‘loopy’ /
zonal meridional and the rest of his thesis picks up from there.
There’s a decent discussion of it here:
That interestingly enough leads to a precursor page that points back to here as a tip to a paper ;-) Gotta love it when things “just grow” ;-)
https://chiefio.wordpress.com/2011/12/27/open-talk-tuesday-5/ where I referenced:
while Tallbloke links to the top page:
So I think that some kind of integration of that ‘flow of solar energy’ process through the air and water would help Salvatore’s presentation. Then again, it would make it far too long for a comment.
I hope this ‘bringing together of links’ and the comment is helpful in gathering what needs to be looked at in one place. Even if I don’t sort out all the bits or illustrate where there might be linkages. IMHO, Milankovitch sets the background regime of ocean current stability and ice caps. D.O. / Bond Event cycles are periodic and driven externally, most likely via lunar tidal effects; and manifest in two different ways for the same event when in glacial vs interglacial status. Then the Sun stirs the pot (perhaps via an orbital resonance driven timing connection) and the atmosphere / water energy flows change.
When these cycles line up in different ways, you get anything from a nice warm spring, to a frozen ice age glacial, and several cycles in between of variously about 54-60 years, 1500 years, 5000 years (lunar), and even 100,000 – 120,000 years. The major ‘unclear bit’ being just how close we are to making the D.O. Event / Bond Event swap and enter into a glacial ocean instability mode.
Milankovitch has us “close”. D.O. / Bond looks like “now is close to an approaching cold swap after a warm spike”. And the 60 year PDO / AMO swaps have happened. Plus we have the sleepy sun in a funk like we’ve not seen for about 200 years; as the solar cycle switches out the UV. Just how perfectly aligned these are is not known as there is wide error on some bits, like just how precise is that 1500 years and just when was the last one. To me it looks like “spot on” for now on the 1500 year, but I could easily be wrong as the data do not support hard conclusions. Just informed speculation.
With that, I’m off to get some tea and then I’m going to do more reading / thinking about what Salvatore Del Prete posted, as I’ve not got it all soaked up yet.