5 Million years of cooling

Reblogged from Clive Best:

Why did the earth cool ~6C during the Pleistocene resulting in the current deep ~100 Ky glacial cycles? The most probable cause  is plate tectonics – the opening of the Atlantic and continuing rise of the Himalayas after India collided with Asia. Less well known though is the increasing height of the Andes, Greenland and Western US as shown below. All  data are from the PaleoDEM project

an alternative view of this is though contour plots

We can quantify the net change in land topography by calculating the surface area of the earth above a certain height. This shows that over the last 5 million years there has been an increase in land surfaces above 3000m altitude by 5.4 million square km. That figure represents a net global increase of 56% in such high altitude land masses. This land movement is concentrated in the Himalayas, the western coasts of America and Greenland. These last two extend into high latitudes where changes in albedo are important. So how might this affect this global climate?

1. High altitudes are colder simply due to the fall in temperature with lapse rate. Above 3000m is something like 20C colder than at sea level.  Moisture falls as snow and glaciers develop.

2. A 50% increase in glaciated areas increases global albedo thereby reducing net incoming solar radiation slightly, which I estimate at about 0.5% or up to 2W/M2.  Perhaps just as important a result is that Milankovitch orbital forcing gets amplified as more land remains permanently glaciated at higher latitudes. This amplification effect is evident in the Ice Volume data.



When did Antarctica become permanently ice covered? Prior to 2.5My ago the “West Antarctic Ice Sheet and Antarctic Peninsula Ice Sheets together grew successively larger, with periodic collapses during interglacials. During periods of West Antarctic Ice Sheet absence, the Antarctic Peninsula Ice Sheet remained as a series of island ice caps” (source). This might also explain why initially glacial cycles followed the obliquity cycle since NH insolation and SH insolation are out of phase. Changes in Ice volume partially cancel if Antarctica also contributes to sea levels due to land based melt-back. In this case the MPT (Mid Pleistocene Transition) may represent the end of this cancelation effect  and the start  of NH dominance.

Solar input to high latitudes and the global ice volume

Climate Etc.

by Donald Rapp, Ralf Ellis and Clive Best

A review of the relationship between the solar input to high latitudes and the global ice volume over the past 2.7 million years.

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Obliquity, inclination and eccentricity of Earth – a model: Part 2

Tallbloke's Talkshop

Kepler’s trigon – the orientation of consecutive Jupiter-Saturn synodic periods, showing the repeating triangular shape (trigon).
This of course follows on from the very recent Part 1 of the model. Since Jupiter and Saturn are the dominant planets in our solar system, we can speculate that they may have a significant effect on the obliquity of smaller bodies. Or they may not – no-one knows, but we can look at possible evidence.
– – –
Precession of the Jupiter-Saturn conjunction (J-S) was worked out by Kepler centuries ago, as shown in his diagram to the right.

‘As successive great conjunctions occur nearly 120° apart, their appearances form a triangular pattern. In a series every fourth conjunction returns after some 60 years in the vicinity of the first. These returns are observed to be shifted by some 7–8°’ – Wikipedia.

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Obliquity, inclination and eccentricity of Earth – a model: Part 1

Tallbloke's Talkshop

Earth’s Axial Tilt, or Obliquity [Credit: Wikipedia]
First let’s get the approximate target numbers for the model.

‘The inclination of Earth’s orbit varies with respect to the solar system’s invariant plane with a period of roughly 71000 years.
. . .
Taken in conjunction with the 26000-year spin-axis precession, the 71000-year orbit precession causes a 41000-year oscillation in the tilt of the earth’s axis, about plus or minus 1.3 degrees from its average value of 23.3 degrees. This number is not absolutely stable – it depends on the combined positions of all the planets through time.’

Astronomy: precession of Earth (Washington State University)
– – –
Origin of the 100 kyr Glacial Cycle: eccentricity or orbital inclination?

‘Spectral analysis of climate data shows a strong narrow peak with period ~ 100 kyr, attributed by the Milankovitch theory to changes in the eccentricity of the earth’s orbit. The narrowness…

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CO2 Not So Much, 60 Year Cycle Paper Actually Got Published

Reblogged from Musings from the Chiefio:

The article is cited in a couple of other places. I ran into it here:


Where Tallbloke points to the Elsevier / Science Direct origin (where it is paywalled…)

This supports the idea that temperature cycles in the region of 60 years are very likely a common feature of Earth’s climate.

Deploying a new technique for the first time in the region, geoscientists at the University of Massachusetts Amherst have reconstructed the longest and highest-resolution climate record for the Northeastern United States, which reveals previously undetected past temperature cycles and extends the record 900 years into the past, well beyond the previous early date of 1850, reports Phys.org.

And points at the description of the article at phys.org:


As Miller explains, they used a relatively new quantitative method based on the presence of chemical compounds known as branched glycerol dialkyl glycerol tetra ethers (branched GDGTs) found in lakes, soils, rivers and peat bogs around the world. The compounds can provide an independent terrestrial paleo-thermometer that accurately assesses past temperature variability.

Miller says, “This is the first effort using these compounds to reconstruct temperature in the Northeast, and the first one at this resolution.” He and colleagues were able to collect a total of 136 samples spanning the 900-year time span, many more than would be available with more traditional methods and from other locations that typically yield just one sample per 30-100 years.

I make that about a 6 2/3 year long duration per sample. So 9 samples per 60+ year cycle. A bit coarse but it ought to resolve with 4 to 5 samples per arc of excursion.

I find it a bit amusing that they are all worked up about having rediscovered the Medieval Warm Period and the Little Ice Age; but OK, at least we’re finally getting back to reality. They are amazed at the “new” finding of the same 60ish year cycle that has been found just about everywhere anyone actually looks for it. OK… All bolding by me.

In their results, Miller says, “We see essentially cooling throughout most of the record until the 1900s, which matches other paleo-records for North America. We see the Medieval Warm Period in the early part and the Little Ice Age in the 1800s.” An unexpected observation was 10, 50-to-60-year temperature cycles not seen before in records from Northeast U.S., he adds, “a new finding and surprising. We’re trying to figure out what causes that. It may be caused by changes in the North Atlantic Oscillation or some other atmospheric patterns. We’ll be looking further into it.”

He adds, “We’re very excited about this. I think it’s a great story of how grad students who come up with a promising idea, if they have enough support from their advisors, can produce a study with really eye-opening results.” Details appear in a recent issue of the European Geophysical Union’s open-access online journal, Climate of the Past.

The authors point out that paleo-temperature reconstructions are essential for distinguishing human-made climate change from natural variability, but historical temperature records are not long enough to capture pre-human-impact variability. Further, using conventional pollen- and land-based sediment samples as climate proxies can reflect confounding parameters rather than temperature, such as precipitation, humidity, evapo-transpiration and vegetation changes.

Or put more succinctly, our thermometer record is short and lousy and our proxy record is pretty damn poor too.

Then TallBloke also points at a couple of other links. Here’s the paywall:


Anthropogenic CO2 warming challenged by 60-year cycle

Author François Gervais


Time series of sea-level rise are fitted by a sinusoid of period ~ 60 years, confirming the cycle reported for the global mean temperature of the earth. This cycle appears in phase with the Atlantic Multidecadal Oscillation (AMO). The last maximum of the sinusoid coincides with the temperature plateau observed since the end of the 20th century. The onset of declining phase of AMO, the recent excess of the global sea ice area anomaly and the negative slope of global mean temperature measured by satellite from 2002 to 2015, all these indicators sign for the onset of the declining phase of the 60-year cycle. Once this cycle is subtracted from observations, the transient climate response is revised downwards consistent with latest observations, with latest evaluations based on atmospheric infrared absorption and with a general tendency of published climate sensitivity. The enhancement of the amplitude of the CO2 seasonal oscillations which is found up to 71% faster than the atmospheric CO2 increase, focus on earth greening and benefit for crops yields of the supplementary photosynthesis, further minimizing the consequences of the tiny anthropogenic contribution to warming.

I found a non-paywall copy up here:


So download your copy while you can…

A nice summary of other 60 year-ish cycle evidence in this link also from TallBloke:

So what are these “branched glycerol dialkyl glycerol tetraethers”?
Found that answer here:


From their Figure 2:



Strange things made in the membrane of various microbes in the water column that change with the temperature.

From the actual paper intro:

A cycle of period ~60 years has been reported in global mean temperature of the earth (Schlesinger and Ramankutty, 1994; Ogurtsov et al., 2002; Klyashtorin and Lyubushin, 2003; Loehle, 2004; Zhen-Shan and Xian, 2007; Carvalo et al., 2007; Swanson and Tsonis, 2009; Scafetta, 2009; Akasofu, 2010; D’Aleo and Easterbrook, 2010; Loehle and Scafetta, 2011; Humlum et al., 2011; Chambers et al., 2012; Lüdecke et al., 2013; Courtillot et al., 2013; Akasofu, 2013; Macias et al., 2014; Ogurtsov et al., 2015). This cycle and others of smaller amplitude were found to be correlated with the velocity of the motion of
the sun with respect to the center of mass of the solar system (Scafetta, 2009). This cycle is also in phase with AMO index (Knudsen et al., 2011; McCarthy et al., 2015).
Section 2 will search for additional signatures of this 60-year cycle in major components and sensitive indicators of climate. The impact on climate of the CO2 emitted by burning of fossil fuels is a long-standing debate illustrated by 1637 papers found in the Web of Science by crossing the keywords

[anthropogenic] AND [greenhouse OR CO2] AND [warming]

This is to be compared to more than 1350 peer-reviewed papers which express reservations about dangerous anthropogenic CO2 warming and/or insist on the natural variability of climate (Andrew,2014). The transient climate response (TCR) is defined as the change in global mean surface temperature at the time of doubling of atmospheric CO2 concentration. The range of uncertainty reported by AR5 (2013) is very wide, 1–2.5 °C. More recent evaluations, later than the publication of AR5 (2013), focus on low values lying between 0.6 °Cand 1.4 °C (Harde, 2014; Lewis and Curry, 2014; Skeie et al., 2014; Lewis, 2015). The infrared absorption of CO2 is well documented since the availability of wide-band infrared spectrometry (Ångström, 1900).

OMG! Actually talking about solar motion and AMO connections! Next thing you know they will discover the lunar cycle involvement and how tides are directly shifting the ocean and air flows as part of those celestial motions…

The intro then goes into a discussion of the IR spectra and transmission where it finds the approved models lacking and also finds that yes, Virginia, we have had a pause in temperature rises…

The controversy has reached a novel phase because, contrary to CMIP3 and CMIP5 warming projections (AR5, 2013), global mean temperatures at the surface of the earth display a puzzling « plateau » or « pause » or « hiatus » since the end of the last century (McKitrick, 2014). This hiatus seems to have encouraged climate modelers to refrain from exaggerated warming projections.

The paper is full of many such goodies. It goes on to find a large 60 year cycle effect and a very muted CO2 effect.

Skipping down to the summary:

Dangerous anthropogenic warming is questioned (i) upon recognition of the large amplitude of the natural 60–year cyclic component and (ii) upon revision downwards of the transient climate response consistent with latest tendencies shown in Fig. 1, here found to be at most 0.6 °C once the natural component has been removed, consistent with latest infrared studies (Harde, 2014). Anthropogenic warming well below the potentially dangerous range were reported in older and recent studies (Idso, 1998; Miskolczi, 2007; Paltridge et al., 2009; Gerlich and Tscheuschner, 2009; Lindzen and Choi, 2009, 2011; Spencer and Braswell, 2010; Clark, 2010; Kramm and Dlugi, 2011; Lewis and Curry, 2014; Skeie et al., 2014; Lewis, 2015; Volokin and ReLlez, 2015). On inspection of a risk of anthropogenic warming thus toned down, a change of paradigm which highlights a benefit for mankind related to the increase of plant feeding and crops yields by enhanced CO2 photosynthesis is suggested.

I strongly recommend a download and careful reading of the paper.

Ocean Heat Content Surprises

Here are Dr. Curry’s summarizing comments:

JC reflections

After reading all of these papers, I would have to conclude that if the CMIP5 historical simulations are matching the ‘observations’ of ocean heat content, then I would say that they are getting the ‘right’ answer for the wrong reasons. Not withstanding the Cheng et al. paper, the ‘right’ answer (in terms of magnitude of the OHC increase) is still highly uncertain.

The most striking findings from these papers are:

  • the oceans appear to have absorbed as much heat in the early 20th century as in recent decades (stay tuned for a forthcoming blog post on the early 20th century warming)
  • historical model simulations are biased toward overestimating ocean heat uptake when initialized at equilibrium during the Little Ice Age
  • the implied heat loss in the deep ocean since 1750  offsets one-fourth of the global heat gain in the upper ocean.
  • cooling below 2000 m offsets more than one-third of the heat gain above 2000 m.
  • the deep Pacific cooling trend leads to a downward revision of heat absorbed over the 20th century by about 30 percent.
  • an estimated 20% contribution by geothermal forcing to overall global ocean warming over the past two decades.
  • we do not properly understand the centennial to millennia ocean warming patterns, mainly due to a limited understanding of circulation and mixing changes

These findings have implications for:

  • the steric component of sea level rise
  • ocean heat uptake in energy balance estimates of equilibrium climate sensitivity
  • how we initialize global climate models for historical simulations

While each of these papers mentions error bars or uncertainty, in all but the Cheng et al. paper, significant structural uncertainties in the method are discussed. In terms of uncertainties, these papers illustrate numerous different methods of estimating of 20th century ocean heat content.  A much more careful assessment needs to be done than was done by Cheng et al., that includes these new estimates and for a longer period of time (back to 1900), to understand the early 20th century warming.

In an article about the Cheng et al. paper at Inside Climate News, Gavin Schmidt made the following statement:

“The biggest takeaway is that these are things that we predicted as a community 30 years ago,” Schmidt said. “And as we’ve understood the system more and as our data has become more refined and our methodologies more complete, what we’re finding is that, yes, we did know what we were talking about 30 years ago, and we still know what we’re talking about now.”

Sometimes I think we knew more of what we were talking about 30 years ago (circa the time of the IPCC FAR, in 1990) than we do now: “it aint what you don’t know that gets you in trouble. It’s what you know for sure that just aint so.”

The NASA GISS crowd (including Gavin) is addicted to the ‘CO2 as climate control knob’ idea.  I have argued that CO2 is NOT a climate control knob on sub millennial time scales, owing to the long time scales of the deep ocean circulations.

A talking point for ‘skeptics’ has been ‘the warming is caused by coming out of the Little Ice Age.’   The control knob afficionadoes then respond ‘but what’s the forcing.’  No forcing necessary; just the deep ocean circulation doing its job.  Yes, additional CO2 will result in warmer surface temperatures, but arguing that 100% (or more) of the warming since 1950 is caused by AGW completely neglects what is going on in the oceans.


[Hifast Note: The comment thread at Dr. Curry’s Climate Etc. is essential reading as well.]


Climate Etc.

by Judith Curry

There have several interesting papers on ocean heat content published in recent weeks, with some very important implications.

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Greenland Is Way Cool

Reblogged from Watts Up With That:

Guest Post by Willis Eschenbach

As a result of a tweet by Steve McIntyre, I was made aware of an interesting dataset. This is a look by Vinther et al. at the last ~12,000 years of temperatures on the Greenland ice cap. The dataset is available here.

Figure 1 shows the full length of the data, along with the change in summer insolation at 75°N, the general location of the ice cores used to create the temperature dataset.

Figure 1. Temperature anomalies of the Greenland ice sheet (left scale, yellow/black line), and the summer insolation in watts per square metre at 75°N (right scale, blue/black line). The red horizontal dashed line shows the average ice sheet temperature 1960-1980.

I’ll only say a few things about each of the graphs in this post. Regarding Figure 1, the insolation swing shown above is about fifty watts per square metre. Over the period in question, the temperature dropped about two and a half degrees from the peak in about 5800 BCE. That would mean the change is on the order of 0.05°C for each watt per square metre change in insolation …

From about 8300 BCE to 800 BCE, the average temperature of the ice sheet, not the maximum temperature but the average temperature of the ice sheet, was greater than the 1960-1980 average temperature of the ice sheet. That’s 7,500 years of the Holocene when Greenland’s ice sheet was warmer than recent temperatures.

Next, Figure 2 shows the same temperature data as in Figure 1, but this time with the EPICA Dome C ice core CO2 data.

Figure 2. Temperature anomalies of the Greenland ice sheet (left scale, yellow/black line), and EPICA Dome C ice core CO2 data, 9000 BCE – 1515 AD (right scale, blue/black line)

Hmmm … for about 7,000 years, CO2 is going up … and Greenland temperature is going down … who knew?

Finally, here’s the recent Vinther data:

Figure 3. Recent temperature anomalies of the Greenland ice sheet.

Not a whole lot to say about that except that the Greenland ice sheet has been as warm or warmer than the 1960-1980 average a number of times during the last 2000 years.

Finally, I took a look to see if there were any solar-related or other strong cycles in the Vinther data. Neither a Fourier periodogram nor a CEEMD analysis revealed any significant cycles.

And that’s the story of the Vinther reconstruction … here, we’ve had lovely rain for a couple of days now. Our cat wanders the house looking for the door into summer. He goes out time after time hoping for a different outcome … and he is back in ten minutes, wanting to be let in again.

My best to all, rain or shine,


Study shows the Sahara swung between lush and desert conditions every 20,000 years, in sync with monsoon activity

Tallbloke's Talkshop

Image credit: BBC
These climatic swings (cycles) were in sync with changes in the Earth’s tilt, say the researchers. They therefore believe ice ages are not the primary factor in these swings.

The Sahara desert is one of the harshest, most inhospitable places on the planet, covering much of North Africa in some 3.6 million square miles of rock and windswept dunes.

But it wasn’t always so desolate and parched, reports Phys.org.

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University of Exeter research sheds new light on what drove last, long-term global climate shift

Reblogged from Watts Up With That:

Public Release: 19-Dec-2018

The quest to discover what drove the last, long-term global climate shift on Earth, which took place around a million years ago, has taken a new, revealing twist.

A team of researchers led by Dr Sev Kender from the University of Exeter, have found a fascinating new insight into the causes of the Mid-Pleistocene Transition (MPT) – the phenomenon whereby the planet experienced longer, intensified cycles of extreme cold conditions.

While the causes of the MPT are not fully known, one of the most prominent theories suggests it may have been driven by reductions in glacial CO2 emissions.

Now, Dr Kender and his team have discovered that the closure of the Bering Strait during this period due to glaciation could have led the North Pacific to become stratified – or divided into distinct layers – causing CO2 to be removed from the atmosphere. This would, they suggest, have caused global cooling.

The team believe the latest discovery could provide a pivotal new understanding of how the MPT occurred, but also give a fresh insight into the driving factors behind global climate changes.

The research is published in Nature Communications on December 19th 2018.

Dr Kender, a co-author on the study from the Camborne School of Mines, based at the University of Exeter’s Penryn Campus in Cornwall said: “The subarctic North Pacific is composed of some of the oldest water on Earth, which has been separated from the atmosphere for such a long time that a high concentration of dissolved CO2 has built up at depth. When this water upwells to the surface, some of the CO2 is released. This is thought to be an important process in geological time, causing some of the global warming that followed past glaciations.

“We took deep sediment cores from the bottom of the Bering Sea that gave us an archive of the history of the region. By studying the chemistry of sediment and fossil shells from marine protists called foraminifera, we reconstructed plankton productivity, and surface and bottom water masses. We were also able to better date the sediments so that we could compare changes in the Bering Sea to other global changes at that time.

“We discovered that the Bering Sea region became more stratified during the MPT with an expanded intermediate-depth watermass, such that one of the important contributors to global warming – the upwelling of the subarctic North Pacific – was effectively curtailed.”

The Earth’s climate has always been subjected to significant changes, and over the past 600,000 years and more it has commonly oscillated between warm periods, similar today, and colder, ‘glacial’ periods when large swathes of continents are blanketed under several kilometres of ice.

These regular, natural changes in the Earth’s climate are governed by changes in how the Earth orbits around the sun, and variations in the tilt of its axis caused by gravitational interactions with other planets.

These changes, known as orbital cycles, can affect how solar energy is dispersed across the planet. Some orbital cycles can, therefore, lead to colder summers in the Northern Hemisphere which can trigger the start of glaciations, while later cycles can bring warmer summers, causing the ice to melt.,

These cycles can be influenced by a host of factors that can amplify their effect. One of which is CO2 levels in the atmosphere.

As the MPT occurred during a period when there were no apparent changes in the nature of the orbit cycles, scientists have long been attempting to discover what drove the changes to take place.

For this research, Dr Kender and his team drilled for deep-sea sediment in the Bering Sea, in conjunction with the International Ocean Discovery Program, and measured the chemistry of the fossil shells and sediments.

The team were able to create a detailed reconstruction of oceanic water masses through time – and found that the closure of the Baring Strait caused the subarctic North Pacific became stratified during this period of glaciation.

This stratification, that argue, would have removed CO2 from the atmosphere and caused global cooling.

Dr Kender added: “Today much of the cold water produced by sea ice action flows northward into the Arctic Ocean through the Bering Strait. As glaciers grew and sea levels fell around 1 million years ago, the Bering Strait would have closed, retaining colder water within the Bering Sea. This expanded watermass appears to have stifled the upwelling of deep CO2-rich water and allowed the ocean to sequester more CO2 out of the atmosphere. The associated cooling effect would have changed the sensitivity of Earth to orbital cycles, causing colder and longer glaciations that characterise climate ever since.

“Our findings highlight the importance of understanding present and future changes to the high latitude oceans, as these regions are so important for long term sequestration or release of atmospheric CO2.”

It’s the gradient, stupid!

Reblogged form Watts Up With That:

How does the Sun drive climate change?

Guest Post by Javier

The dispute between scholars that favor a periodical interpretation of climate changes, mostly based on astronomical causes, and those that prefer non-periodical Earth-based explanations has a long tradition that can be traced to the catastrophism-uniformitarianism dispute and how the theory of ice ages (now termed glaciations) fitted in.

Prior to the scientific proposal of ice ages in 1834, most scholars that cared about the issue believed that the Earth had been progressively cooling from a hot start, as tropical fossils at high latitudes appeared to support. By 1860 scholars had been convinced by evidence that not one but several glaciations had taken place in the distant past. By then scientists trying to explain the cause of past glaciations were split in two. Those following Joseph Adhémar, who had already proposed orbital variations in 1842, and those following John Tyndall, who proposed that they were due to changes in GHGs (greenhouse gases) in 1859, particularly water vapor.

For a time, the anti-cyclical, pro-GHG camp had the advantage, after James Croll’s hypothesis was rejected, and Svante Arrhenius in 1894 proposed CO2 as the responsible GHG. But then, doubts about the CO2 effect and a new formulation of the cyclical astronomical hypothesis by Milankovitch appeared that fit popular geological reconstructions of past glaciations. This swung the field again.

By the late 1940’s Milankovitch theory was well established, particularly in Europe, but not so much in America where reconstruction of Laurentide ice-sheet changes did not match the theory very well. But in the 1950’s a new consensus formed. The GHG theory was reinforced by Suess, Revelle, and Keeling’s work, while carbon dating led to glacial reconstructions at odds with Milankovitch theory.

In the 1960’s and early 70’s Milankovitch theory was discredited with only a handful of followers left. The anti-cyclical, GHG explanation enjoyed wide consensus, but due to the cooling at the time, scholars believed other factors must be at play. Then disaster struck for the anti-cyclical camp. In 1976, Hays, Imbrie, and Shackleton, analyzing Indian Ocean benthic cores for the past 450,000 years and showed that glaciations followed some of Milankovitch frequencies within 5% error. A 140-year quest had ended, and the cyclical orbital supporters had won.

Of course, GHG supporters are bad players and did not accept the defeat graciously. Since it was soon discovered in ice cores that GHGs followed orbital changes (as they should), it was soon proposed (and accepted without evidence) that they were required to amplify the orbital changes and to maintain inter-hemispheric synchroneity. Trying to turn the defeat into a victory, they claim that the frequency is set by Milankovitch but a great deal of glacial-interglacial climate changes are due to GHG changes.

You would think that after showing that climate was cyclical and astronomically based, propositions that other astronomical phenomena (like lunar periodicities or solar variability periodicities), might affect climate would at least be given the benefit of doubt. But no. The anti-cyclical camp enjoys centennial beatings by the cyclical mavericks, so they are building up for the next one by flatly rejecting any significant climatic effect from periodical solar changes. Apparently, they are undeterred by the evidence showing most periods of low solar activity during the Holocene are associated with cooling and atmospheric circulation and precipitation changes, like the LIA. There are about 10 abrupt climate events (ACEs) associated with low solar activity during the Holocene. Some have names like the pre-boreal and boreal oscillations, or the 9.3 or 2.7 kyr events, showing that the most frequent cause for ACEs is prolonged low solar activity.

I have already shown some evidence for that in my previous articles:

Do-It-Yourself: The solar variability effect on climate

Do-It-Yourself: Solar variability effect on climate. Part II

I have also shown that ENSO is under solar control:

Solar minimum and ENSO prediction

Yet the anti-cyclical crowd (IPCC included) takes refuge in the bean-counting argument that solar variability is only 0.1% and therefore too small to produce much of a change. This only shows how narrowly focused their view of climate is. They think that Earth’s climate can be explained solely with terms of W/m2 and after all 0.1% is only 1.4 W/m2 over the 11-yr cycle (solar irradiation), adjusted to only 0.34 W/m2 annual average insolation change at top-of-the-atmosphere (TOA) at 1 AU. However, the Earth received the same TOA insolation during the Last Glacial Maximum as now, so climate is clearly not a case of bean-counting Watts.

Today I am going to show you how solar variability affects Earth’s rotation speed, and why it is important. This issue was raised several times in 2010, but it is not understood by most:



Changes in the rotation speed of the Earth are measured as variations in the length of day (ΔLOD) defined as the difference between the astronomically determined duration of the day and 86,400 Standard International (SI) seconds. ΔLOD has been measured daily down to a 20 microsecond (µs) precision by interferometry since 1962. Annual changes at 1 millisecond (ms) precision have been reconstructed for the telescope era from astronomical observations. Variations in ΔLOD on annual and seasonal (semi-annual) time scales are highly correlated with angular momentum fluctuations within the atmosphere, mainly due to changes in zonal winds. The averaged annual and semi-annual oscillations in ΔLOD feature almost equal amplitudes of approximately 0.36 ms.

The semi-annual oscillation in ΔLOD has the following characteristics:

From November to January the Earth accelerates to ~ 0.2 ms-day (ΔLOD changes by -0.2 ms). Then it decelerates by nearly the same amount by April. Afterwards it accelerates to ~ 1 ms-day by July (ΔLOD change of -1 ms), before decelerating back to the initial value by the next November. The average amplitude is ~ 0.35 ms, but the NH winter component is much smaller than the SH winter component (see figure 1, inset).

This change is caused by the angular momentum of the atmosphere being higher in winter because the meridional circulation is much stronger during that season. This is the result of the winter pole receiving very little insolation as the Sun is above the opposite hemisphere. The dark pole becomes colder and the latitudinal temperature gradient steeper, and as a result more heat needs to be transported poleward, activating the meridional circulation in that hemisphere. The asymmetry of the NH (Northern Hemisphere) winter and SH (Southern Hemisphere) winter components of ΔLOD is due to the asymmetry in land masses between hemispheres having a strong effect on wind circulation.

Le Mouël et al., 2010 showed that the semi-annual component of ΔLOD responds to solar variability. This is an extremely important result highlighted only by a few skeptics and ignored by everybody else. Part of the problem is that the article’s method to show it is quite complicated, and most people did not understand the article or its implications. Let’s try a simpler way.

Let’s concentrate only on the NH winter acceleration (ΔLOD decrease) that by being smaller, more clearly shows the effect. We start with LOD data from the International Earth Rotation and Reference System Service EOP C04 IAU2000A file:


This is a 20,700 data point file with daily ΔLOD values since 1962. It is converted to monthly values to work with only 680 points and eliminate all the oceanic and atmospheric tidal higher frequencies. The result is shown in figure 1.

Figure 1. Monthly ΔLOD. The inset shows two years of data with four semi-annual components. What I am going to measure every year is the acceleration (ΔLOD decrease) of the NH-winter component.

The NH winter trough in ΔLOD might take place in Dec-Jan-Feb (DJF), so for every year I select the lowest value among those three months, and then subtract from that value the highest value (ΔLOD fall peak) within the four prior months to the one selected. If there is no peak value in the 4 prior months this means there was no ΔLOD decrease the prior fall and I introduce a zero (it happened in 1983 and 1993, see figure 1). The result is a number for every year measuring the Earth’s acceleration from Oct-Nov to DJF in milliseconds, that varies between 0 and -0.9 ms.

As ΔLOD is affected by anything that affects the angular momentum of the atmosphere, like ENSO, the obtained NH winter acceleration yearly dataset is noisy, so we smooth it with a triangular filter (ΔLODsm[t] = 0.5*ΔLOD[t] + 0.25*ΔLOD[t-1] + 0.25*ΔLOD[t+1]). The result is then compared to solar activity, in this case monthly 10.7 cm flux smoothed with a gaussian filter. It is shown in figure 2.

Figure 2. NH winter ΔLOD vs. Solar activity

This is a simpler way to look at the dependence of the speed of rotation of the Earth on solar variability. Let’s remember that Le Mouël et al., 2010, and Paul Vaughan here at WUWT, showed that both semi-annual components respond to solar variability, and not only the NH winter one that I have shown. The agreement with solar data is even better using both components (see Le Mouël et al., 2010 or the WUWT links above).

Now we know how solar variability affects climate despite being only a 0.1% change in TSI. But before explaining that, let me explain why ΔLOD is so important for climate.

Changes in Earth’s rotation speed act as a climate integrator, reflecting changes in atmospheric circulation that then cause changes in temperature. ΔLOD is not known to be a cause for climate change, but a way of measuring it that responds in real time to changes in the angular momentum of the atmosphere. It is therefore a leading indicator of climate change. It is not known to respond to radiative changes and therefore to CO2, and thus it does not appear in the IPCC reports. I searched the WG1 AR5 report and could not find any mention of it. Yet, in 1976 Kurt Lambeck and Anny Cazenave reported that changes in ΔLOD for the past 150 years correlate well to a variety of climate indices, and they produced one of the few trend-change climate predictions that have proven accurate. They indicated that since ΔLOD had started accelerating in 1972 (see figure 1) the observed cooling trend was about to end. 1976 was the exact year when that happened.

Adriano Mazzarella in 2013, and Mazzarella and Scafetta in 2018 showed the good correlation between several climate indices and ΔLOD. In figure 3 I compare, as he did, yearly NH SST from HadSST3.1 and yearly ΔLOD (both linearly detrended for the period shown).

Figure 3. Detrended changes in Northern Hemisphere Sea Surface Temperature and detrended changes in Earth’s rotation speed (ΔLOD inverted).

On average changes in ΔLOD precede changes in SST by 4 years, indicating that atmospheric changes affecting ΔLOD are also responsible for cooling or warming the ocean surface.

So, how does the Sun affect ΔLOD? As figure 2 shows, when solar activity is high the winter NH acceleration does not take place, and when solar activity is low the winter NH acceleration is greater. So, the winter NH atmospheric circulation suffers more profound changes when solar activity is low. Low solar activity is also associated with a stronger activation of the winter meridional circulation that causes stronger meridional heat transport towards the poles and more frequent winter blocking. Further, low solar activity is associated with persistent winter negative NAO (North Atlantic Oscillation) conditions over high latitudes. The subpolar oceanic gyre then becomes weaker. A warmer North Atlantic current feeds more snow to Scandinavia (remember the great 2010 snowstorm that blanketed Great Britain and several other European countries), while weaker Westerlies result in a more southward winter storm track that dries Northern Europe and wets the Mediterranean.

During the LIA (Little Ice Age) the planet got stuck in this situation during years and decades of low solar activity. And every 200 years there was a Grand Solar Minimum that lasted for 80-150 years, so it got cooler and cooler and glaciers grew and grew, until solar activity returned to normal and there was a recovery. It was a slow cooling and it is a slow warming. Long-term solar activity has been growing to the late 20th century (figure 4). According to my calculations of solar periodicities, long-term solar activity should continue being high for at least another 100 years, but it won’t increase much more over the levels seen in the second half of the 20th-century. So, it should not significantly contribute to additional global warming.

Because of the land mass asymmetry between hemispheres, the atmospheric circulation changes caused by solar variability are proportionally smaller in the Southern Hemisphere. Although the effect is global it is stronger in the Northern Hemisphere, providing an explanation for the unexplained fact that climate change is more intense in that hemisphere. LIA effects were also stronger in the Northern Hemisphere, to the point of some suggesting it was a regional phenomenon. It is a feature of asymmetric solar variability effect on hemispheric atmospheric circulation, and the reason I selected NH-winter acceleration to show the effect.

Figure 4 shows how solar activity changed during the LIA and how it has been increasing since. Temperature has been trailing the recovery in solar activity with a delay. While solar activity started recovering after ~ 1700, temperature bottomed a second time in 1810-1840 and only started recovering after the cluster of large volcanic eruptions during the Dalton period (~1790-1840) ended. Temperature is affected by more things than just solar activity.

Figure 4. a) Solar activity reconstruction from 14C record (Muscheler et al., 2007), with a 2nd degree polynomial showing the long-term trend. b) Total solar irradiation reconstruction (Vieira et al., 2011) compared to Northern Hemisphere summer temperature reconstruction (Anchukaitis et al., 2017).

The planet’s climate is determined by the latitudinal temperature gradient, not the average global temperature. The poles are energy sinks to space (particularly in winter) and the efficiency of the poleward heat transport determines how much energy the planet retains, not the amount of CO2 in the atmosphere, which has a much smaller effect. We are studying the thickness of the glass in the windows, when it is the open door to the poles that matters regarding warming. The door has been closing, so the Earth has been warming, and solar variability is responsible, while CO2is just contributing. Zonal wind vertical strength is proportional to the latitudinal temperature gradient and inversely proportional to the Coriolis factor. Solar variability, despite being only 0.1%, shows a demonstrable capacity to affect the zonal/meridional wind balance during winters. There are several possible mechanisms, but a strong possibility is through stratospheric latitudinal temperature gradients due to winter ozone distribution and UV changes with solar variability. These gradients could affect tropospheric wind circulation through changes in geopotential height. Alternatively, the atmosphere is known to expand and contract with solar activity, but this effect is dominated by the rarefied outer atmosphere that has very little mass, and the atmospheric angular momentum changes that affect Earth’s rotation are dominated by the effect of tropospheric winds in the lower 30 km. It could be a combination of solar variability effects over the entire atmosphere acting in the same direction and affecting zonal wind circulation.

The importance of the latitudinal temperature gradient cannot be overstated. Christopher Scotese has been reconstructing the climate of the distant past by reconstructing changes in the latitudinal temperature gradient on a 10-million-year scale over the Phanerozoic. The main difference between a hothouse climate and an icehouse climate is in the gradient, and the average temperature of the planet is just the result of how much energy is moved through the gradient.

When this is sufficiently researched, once again the cyclical climate camp will have given a sound beating to the GHG crowd, let’s hope that this time is for good. And the TSI bean counters will discover that the climate of the planet is a lot more complex than they think and it is not only a matter of W/m2. Simple answers are satisfying, but rarely solve complex questions.

And if you want to know how climate change is going to evolve over the next 4 years, you only have to look at how ΔLOD is evolving now. You will know more about it than the IPCC, Gavin Schmidt, and all the consensus builders looking at their models based on an incorrect paradigm.

I leave for another day how the Moon produces some of the most abrupt cyclical climate change events of the past.


Hays, J. D., Imbrie, J. and Nicholas J. Shackleton. 1976. Variations in the Earth’s orbit: pacemaker of the ice ages. Science 194 (4270), 1121-1132. Link.

Le Mouël, J. L., Blanter, E., Shnirman, M., & Courtillot, V. (2010). Solar forcing of the semi‐annual variation of length‐of‐day. Geophysical Research Letters, 37(15). Link.

Na, S. H., Kwak, Y., Cho, J. H., Yoo, S. M., & Cho, S. (2013). Characteristics of perturbations in recent length of day and polar motion. Journal of Astronomy and Space Sciences, 30, 33-41. Link.

Lambeck, K., & Cazenave, A. (1976). Long term variations in the length of day and climatic change. Geophysical Journal of the Royal Astronomical Society, 46(3), 555-573. Link.

Mazzarella, A. (2013). Time-integrated North Atlantic Oscillation as a proxy for climatic change. Natural Science, 5(01), 149. Link.

Mazzarella, A., & Scafetta, N. (2018). The Little Ice Age was 1.0–1.5° C cooler than current warm period according to LOD and NAO. Climate Dynamics, 1-12. Link.

Muscheler, R., Joos, F., Beer, J., Müller, S. A., Vonmoos, M., & Snowball, I. (2007). Solar activity during the last 1000 yr inferred from radionuclide records. Quaternary Science Reviews, 26(1-2), 82-97. Link.

Anchukaitis, K. J., Wilson, R., Briffa, K. R., Büntgen, U., Cook, E. R., D’Arrigo, R., … & Hegerl, G. (2017). Last millennium Northern Hemisphere summer temperatures from tree rings: Part II, spatially resolved reconstructions. Quaternary Science Reviews, 163, 1-22. Link.

Vieira, L. E. A., Solanki, S. K., Krivova, N. A., & Usoskin, I. (2011). Evolution of the solar irradiance during the Holocene. Astronomy & Astrophysics, 531, A6. Link.

[Update, because of some rogue code that made it into this post, it may appear on your device that you can edit it.  Just refresh to undo any edits you think you’ve made.  No harm. No foul..~ctm]

[HiFast Note:  Lively comment thread at WUWT here.]