Chinese researchers claim they discovered a 500 year solar cycle that may affect climate

This new paper has done some interesting analysis, similar to what we’ve seen done here on WUWT by Willis Eschenbach. It will be interesting to see what he and our resident solar physicist, Dr. Leif Svalgaard have to say about it.


Earth Science Research; Vol. 7, No. 1; 2018

Lihua Ma, Zhiqiang Yin & Yanben Han – National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China


Direct observations of solar activity are available for the past four century, so some proxies reflecting solar activity such as 14C, 10Be and geomagnetic variations are used to reconstruct solar activity in the past. In this present paper, the authors use rectified wavelet power transform and time-averaged wavelet power spectrum to investigate long-term fluctuations of the reconstructed solar activity series. The results show an obvious quasi 500-year cycle exists in the past solar activity. Three reconstructed solar activity series from 14C variations confirm the periodic signals.

1. Introduction

Solar activity has a profound influence upon geodynamics processes, and the Sun directly or indirectly affects some terrestrial phenomena on the Earth. Some studies showed variation of solar activity closely relates to global and regional climate change (Rasmus, 2006; Miyahara et al., 2008; Mendoza & Velasco, 2009; Ogurtsov et al., 2013; Dergachev et al., 2016). After analyzing the solar variation, global and regional sea-surface temperature, Weng (2005) concluded that inter-annual and centennial climate change signals were not purely internal, but also external because of the existence of the solar activity cycle. Kilcik et al. (2008) made use of surface air temperature, pressure and tropospheric absorbing aerosol data as climate parameters and solar flare index data as solar activity indicator, to study effect of solar activity on the surface air temperature of Turkey. With Indian temperature series of more than one-hundred years, Aslam (2014) investigated the influence of solar activity on regional climate. Results indicated that the solar variation may still be contributing to ongoing climate change.

The solar activity can influence atmospheric circulation on various time scales, and variations of the atmospheric circulation then impact precipitation process in some areas (Ratnam et al., 2014). Ma et al. (2007) investigated the connection between Indian summer monsoon rainfall and solar activity series, and believed that the solar variation affects the Indian rainfall variation to some extent. Taking into account reconstructed precipitation series in Huashan mountain area of China and solar variation series, the influence of solar activity on the Huashan mountain precipitation to some extent was found (Ma et al., 2010).

More and more people attach importance to studies about long-term solar variation (Usoskin & Mursula, 2003; Yin et al., 2007; Ma, 2007, 2009). However, direct observations of solar activity in the past four centuries are insufficient to calculate the long-term solar variation. Some proxies including 14C, 10Be and geomagnetic variations can reflect the solar activity. Therefore, solar activity in the past can be reconstructed with these proxies. In this work, rectified continuous wavelet transform reveals quasi ~500-year cycle signals existing in the reconstructed solar activity series.

4. Conclusion

In this work, the reconstructed sunspot number series in the past are analyzed to research for quasi ~500-year cycle signals. Results of the rectified wavelet analysis show the obvious time-variable characteristics exist in the solar variation. Periodic amplitude of this cycle changes with time and it is not a cycle in the strict periodic sense but rather cyclicity with a varying time scale. The quasi ~500-year cycle may be a periodic signal in the solar activity, and attention should be paid to it when the long-term fluctuation in the solar variation is studied.

5. Discussion

Pollen record reflects the dynamics of vertical vegetation zones and temperature change. Using a high-resolution pollen record from a maar annually laminated lake in East Asia, Xu et al. (2014) revealed quasi ~500-year periodic cold-warm fluctuations over the past 5350 years. To investigate the possible influence of the quasi ~500-year signals of solar activity on the pollen record, we calculate scale-averaged wavelet power from 320- to 640-year of solar activity and pollen record series and plot it in Figure 3. Here the first principal component of principal components analysis (PCA F1) loadings of the pollen record series was de-trended using polynomial fit. The residuals are regards as the pollen variation.

The paper (open access) is here:

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January 31, 2018 1:20 pm

Just eyeballing it, there also appears to be an 8000 year cycle in that reconstruction. Peak to peak, and trough to trough, are both about 8000 years.

J Mac
Reply to  Les Johnson
January 31, 2018 4:08 pm

After reading this post and the underlying paper, I really don’t ‘see’ the purported quasi 500-year cycles in the graph. But then, I don’t see any quasi-motos either…..
Wait a minute – That’s a correlation, isn’t it?!!

John Harmsworth
Reply to  J Mac
January 31, 2018 4:54 pm

Quasimodo’s hump looks suspiciously like the 500 year bump.
I know, correlation yada, yada …causation.

January 31, 2018 1:23 pm

The paper also makes this claim:
“It is obviously that solar activity influences pollen variation in East Asia on quasi ~500-year cycle, with a time
advance of nearly 1000 years”.
That alone obviously is such a red flag, that I’ll not attach much significance to the basic claim.
People have been ‘finding’ cycles [or ‘quasi-cycles’] all over the place for centuries. Nothinh new [nor significant] in this paper.

Bad Andrew
Reply to  lsvalgaard
January 31, 2018 1:32 pm

“People have been ‘finding’ cycles [or ‘quasi-cycles’] all over the place for centuries.”
And they found a Miracle Molecule that controls the temperature.

Reply to  lsvalgaard
January 31, 2018 2:18 pm

You’re right.
If you analyze a signal over a certain period, there’s no guarantee that the components you find will exist outside that period. In fact, you should assume the opposite.
Signal analysis is complicated and I would bet that the vast majority of scientists who try to use it don’t understand what they’re doing. In fact, some folks seem to have difficulty with the difference between frequency and period.
One of the best expositions of signal analysis I have seen was this WUWT article. Another is The Scientist and Engineer’s Guide to Digital Signal Processing. link You can download it for free. It’s written from the standpoint of someone who might actually have to analyze signals, rather than giving a rigorous mathematical development. What it does do is to highlight practical things that may trip you up.

Bob boder
Reply to  commieBob
February 1, 2018 5:26 am

“If you analyze a signal over a certain period, there’s no guarantee that the components you find will exist outside that period. In fact, you should assume the opposite.”!!!!
With out a doubt one of the best comments ever posted!

Richard G.
Reply to  commieBob
February 2, 2018 5:06 pm

Before you can find Baby Jesus in your pancake, first you must know what Baby Jesus looks like.
The irony is that when you do finaly find Baby Jesus in your pancake, it is still only a pancake.

Pop Piasa
Reply to  lsvalgaard
January 31, 2018 3:26 pm

Doc, until somebody enlightens me on the solar effects on pollen and the associated metrics I’m as skeptical as I would be if it were based on tree rings.

Reply to  Pop Piasa
January 31, 2018 3:35 pm

You can always employ Javier’s maxim: that you don’t need to know the mechanism if you have a good enough correlation. Example: the Sun is rising every morning, even back when people didn’t know how the mechanism worked [rotating Earth].

Pop Piasa
Reply to  Pop Piasa
January 31, 2018 3:51 pm


Pop Piasa
Reply to  Pop Piasa
January 31, 2018 4:05 pm

Does that also apply to CO2 vs. global temp, if I may be so bold as a student of yours?

Reply to  Pop Piasa
January 31, 2018 5:59 pm

You can always employ Javier’s maxim

Exactly. Mechanisms are overrated and most turn out to be wrong, anyway.
Observation rules. Explanation sucks. Science was built over observations, not over explanations. Darwin didn’t have an explanation, but he had plenty of observations. Wegener didn’t have an explanation, but he had plenty of observations.

Reply to  Pop Piasa
January 31, 2018 7:09 pm

I beg to differ. Observations without a proposed explanation or hypothesis are destined to be ignored. It is only when the contentious hypothesis, correct or incorrect, meets the data that it garners attention.
Darwin had reams of observations, but “Origin of Species” was a hypothesis that synthesized them.
Wegener had observations and a hypothesis with many faulty elements.
Even Michelson-Morley had much data, but it’s news was the data didn’t fit the accepted theory.

Crispin in Waterloo but really in Beijing
Reply to  Pop Piasa
February 1, 2018 12:58 am

Stephen and Javier
I take your point about observations being used to generate some sort of explanation. The odd thing is CAGW which has an explanation contradicted by observations. This being the case, we are subjected to additional explanations one after the other, all of which are in one way or another, in conflict with at least some observations.
If the alarmist community had warned us that the rapid heating of the 20’s and 30’s was about to be repeated, we could all get excited and unified over how we were going to deal with the impending catastrophe that would be the Great Dust Bowl II.
Instead all we have had is a series of wave riders and rent seekers with their attendant troughers and running dogs. Yawn. You are better off joining my War on Cold.

Bob boder
Reply to  Pop Piasa
February 1, 2018 5:19 am

I beg to differ. Observations without a proposed explanation or hypothesis are destined to be ignored. It is only when the contentious hypothesis, correct or incorrect, meets the data that it garners attention.”
True enough, however historically the observation comes first, not so true with CAGW theory.

Reply to  Pop Piasa
February 1, 2018 8:49 am


Observations without a proposed explanation or hypothesis are destined to be ignored.

Even the best of the hypotheses with the most marvelous mechanism can be destroyed by the humblest contradictory observation.
However any good, accurate and careful observation is eternal and can be used by any future hypothesis.
What is still valid from Ancient Greek science is based on the observations and measurements they made, not the explanations that they gave about them. Pythagoras theorem, Archimedes principle, are all observations.
Darwin was an acute observer and described what he saw, individuals being selected over other individuals due to small differences. He essentially expanded to the natural world what animal breeders had known for millennia. He was however unable to explain why individuals were different in the first place and how those differences could be maintained through reproduction instead of being lost.
The origin of species, a book that I have read, is a wonderful massive collection of observations in search of a mechanism, but giving a clear sense that the entire natural world is working under a single set of rules, unknown at the time. Darwin named that set of unknown rules Natural Selection. The mechanism wasn’t worked out for many decades.
Climate science will become a real science when they dump the models and embrace observations.

South River Independent
Reply to  Pop Piasa
February 1, 2018 9:49 am

Let the data speak for themselves.

Gary Pearse
Reply to  lsvalgaard
January 31, 2018 4:10 pm

Does anyone know how much time it takes for a group of plants in one locality to march to a new one where temperature has risen sufficiently to support them at the new locality? The Chinese paper suggests 1000 years. But, unfortunately on the march, 500 years would elapse and halfway, they would get cold, die off and have to start over again. But this cooling would also cool 9ff where they started….wouldnt it? For this faunal “Oscillation” I propose The-Grand-Old-Duke-of-York effect

Pop Piasa
Reply to  Gary Pearse
January 31, 2018 7:49 pm

Well… When you’re up, you’re up…

Reply to  Gary Pearse
February 1, 2018 12:49 am

Depends on the plant. Some seeds can be spread very far in a single season with wind and bird droppings. Some seeds are dormant below the surface just waiting for the right condition and can stay dormant but viable for a very long time. Things like dandelions and burrs can travel a long distance on wind or in the coats of animals. Plants that flower quickly after germination and multiple times per season will spread far very quickly.

Reply to  lsvalgaard
January 31, 2018 6:53 pm

Epicycles, all over again…

January 31, 2018 1:26 pm

It is clearly bogus because, just like Mann used only one tree, they used only one Sun!

Tom in Florida
January 31, 2018 1:45 pm

“The quasi ~500-year cycle may be a periodic signal in the solar activity,…”
Or maybe not.

Pop Piasa
Reply to  Tom in Florida
January 31, 2018 4:17 pm

Maybe “Quasi 500” is a good nameplate for a Tesla vehicle.

Reply to  Pop Piasa
January 31, 2018 6:06 pm

Khazi? “(slang, now chiefly Britain regional) A toilet: a fixture used for urination and defecation (also figuratively). quotations ▼
Well, that plan’s down the khazi. “

Pop Piasa
Reply to  Pop Piasa
January 31, 2018 8:16 pm

Thanks Lee, I really enjoy the international dialogue here and sharing of regional slang.

Reply to  Pop Piasa
January 31, 2018 10:30 pm

Any Ozzie’s out there?

Reply to  Pop Piasa
February 2, 2018 5:43 am

Earnhardt won the Quasi 500 three times.

January 31, 2018 1:49 pm

The last 2000 years of the fig 1 sunspot graph do look remarkably similar to the proxy reconstruction of global climate by the Pages2k project.
But as we all know correlation only means two things doing the same as eachother. Like consumption of cheese increasing the probability of death 💀 from entanglement in one’s bedsheets.

Patrick Powers
January 31, 2018 2:31 pm

Odd how only a few years ago many were ridiculed for suggesting that the sun had any influence on climate. Now of course we know differently and from this article there’s likely to be even more to learn…
I encourage all to follow the motto of the Royal Society which (translated) means ‘Take nobody’s word for it’. Pity the Society doesn’t in this field at least follow its own motto …

Robert of Texas
January 31, 2018 2:31 pm

Reconstructed this compared to reconstructed that, then reconstruct the result… And apply statistics… I remain somewhat skeptical.
(Oh, I guess that means I think the Earth is flat as well… I wonder if I can reconstruct that?)

January 31, 2018 2:39 pm

Make no mistake, nothing ….. nothing ….. comes out of China without a political reason and government sanction. Call me cynical but I see this is a back track on AGW. They see the impending solar minimum and temperature drop, know that CO2 will continue to rise, and that Trump is going to out their Paris Treaty commitment (or I should say lack of it) to the world.

Reply to  markl
January 31, 2018 2:53 pm

After learning the depth of the nonsense and manipulation our own government has been up to, I’m not as smug about criticizing the Chinese as I used to be.

Rhoda R
Reply to  wws
January 31, 2018 4:42 pm

But with the Chinese being the new world leader on climate change, this reorientation away from CO2 toward the sun is refreshing.

Extreme Hiatus
Reply to  wws
January 31, 2018 4:47 pm

“But with the Chinese being the new world leader on climate change, this reorientation away from CO2 toward the sun is refreshing.”
Their only real leadership is trying to sell the most solar panels so the Sun is important to them.

Nick Stokes
Reply to  markl
January 31, 2018 3:40 pm

“comes out of China without a political reason and government sanction”
If the government was pushing this, they would have found a better journal.

Extreme Hiatus
Reply to  Nick Stokes
January 31, 2018 4:45 pm

“If the government was pushing this, they would have found a better journal.”
Like Nature. That seems to be the propagandist’s favorite these days.

Reply to  Nick Stokes
January 31, 2018 5:22 pm

It’s a test announcement.

January 31, 2018 3:11 pm

Willis is gonna blow this up in 3..2..1 🙂

January 31, 2018 3:23 pm

The problem with solar worshipers, happens to be no much different than with the AGW ones…even when the later one call the former as stupid.
No hot spot no AGW, and also no sun doing it…stupid….
Same nullification in both counts, as both RF dependent….
Oh…wait…stupid as as stupid does.

January 31, 2018 3:57 pm

As an econometrician, never trust squiggle matching.

Reply to  ristvan
January 31, 2018 4:15 pm

Translation, please. 🙂

J Mac
Reply to  whiten
January 31, 2018 6:04 pm

The human brain is wired for pattern recognition, a survival trait from countless generations learning to recognize the faint patterns of a predators partial outline camouflaged in natural cover. The same holds true for being able to discern edible plants mixed in with inedible and even poisonous plants of similar shape, size, and color. Think ‘mushrooms’. The best at pattern recognition had higher survival rates and the trait became genetically ingrained. It works against us today, as many will look at graphed random data points, and see ‘patterns’ in the wiggle squiggles. Compounding the problem, inappropriate use of statistical methods can seem to confirm trends, where none exists.

Reply to  whiten
January 31, 2018 9:19 pm

Ever look at a cloud and see a face or a bunny? That is squiggle matching.

Gary Pearse
January 31, 2018 4:22 pm

Wouldnt it be a lark if someone found that the sun was actually responsible for our climate. Apparently they found it to be so on Mercury and other researchers found the lack of sunshine was responsible for the cold weather on Pluto. I know that’s dumb, though. That probably wouldnt even happen.

Extreme Hiatus
Reply to  Gary Pearse
January 31, 2018 4:55 pm

There is already an ongoing experiment that proves the sun’s role. It produces what scientists and others calls seasons. Different parts of the planet have different climates that correlate with the lowest amount of daily sun they receive over the course of a year.
Of course you need to factor in elevation and regional weather patterns influenced by topography and ocean currents but that’s the big picture. Close enough for me at least but then I haven’t factored in the quasis.

Tom in Florida
Reply to  Extreme Hiatus
February 1, 2018 8:31 am

Yes, and those are due to orbital patterns of the Earth not changes in solar activity.

J Mac
Reply to  Gary Pearse
January 31, 2018 6:06 pm

That’s just crazy talk, man! };>)

Tom in Florida
Reply to  Gary Pearse
February 1, 2018 8:32 am

You are addressing insolation not solar activity.

January 31, 2018 4:24 pm

I don’t see a 500 year cycle in the chart. What is in the ‘quasi’?

Steve Zell
January 31, 2018 4:35 pm

If there was a 500-year cycle, we should see about four oscillations every 2000 years in the chart. There seem to be lots of oscillations with periods much less than 500 years, superimposed on a cycle which looks to be about 2500 to 3000 years long, but no real indication of a 500-year cycle on the graph.
Maybe the researchers should have done a Fourier analysis of the data to find the cycle length(s) which best match the data.

January 31, 2018 4:52 pm

Lossa noise, little or no discernable signal.
Anyone for a random walk?

January 31, 2018 5:09 pm

They wrote the conclusion before the discussion.

Michael S. Kelly
January 31, 2018 5:10 pm

This is the first time I’ve seen wavelet analysis applied to climate research. It’s welcome. Much more powerful than Fourier analysis, and the results are generally meaningful rather than misleading.

Peter Sable
Reply to  Michael S. Kelly
January 31, 2018 5:58 pm

nd the results are generally meaningful rather than misleading.

I think you might be wrong, since in this case they didn’t apply the wavelet analysis correctly. They found one 500 year blob in one waveform that matched a 500 year blob in another waveform and said “see, there it is”..
If they had done Fourier analysis, they would have seen nothing above the noise floor.
If you want to see wavelets done right, here’s an excellent paper on looking for El Nino cycles in SST:

John Harmsworth
January 31, 2018 5:12 pm

Well, there’s that pesky LIA again. On the other end of the same 500 year cycle there’s the medieval warm period. Go figure!

George Daddis
January 31, 2018 5:24 pm

From a semi educated layman:
If there are almost an infinite number of drivers for our climate, why would we not expect an infinite number of researchers to find a cycle?

Reply to  George Daddis
January 31, 2018 6:11 pm

No and as a simple example you might be able to follow as a layman lets deal with noise and it’s colours
These sorts of noise have every frequency across whatever range you are studying. In your terms they can be infinitely driven from infinite sources and they all interact with each other. However as you can see by the noise colours you can still end up with and overall characteristic you can easily identify.
So you can have infinite drivers but the real question is how variable and what level are the drivers, which is the bit your questions leaves left out. For example if you have ransom infinite drivers and they all vary equally from 0 to max you get the equivalent of white noise.
So the question isn’t about infinite drivers, it’s about how the drivers are varying and across what range.
Universe and Planentary motion also works the same way there are infinite drivers of gravitational attraction working on our earth and each of them is varying over time. So Earth still plots a predictable path around the sun and in a pattern you can easily identify regardless of the infinite forces of gravity working on it.

January 31, 2018 5:48 pm

It is a rather poor article. Their own data shows that the 500-year periodicity is found only between 1200-200 BC for the past 6000 years. And then the pollen 500-year periodicity takes place between 200 BC and 1000 AD, outside the solar periodicity. The figure above shows this clearly.
Sometimes one has to scratch the head and wonder about how some journals conduct peer review.

Nick Stokes
Reply to  Javier
January 31, 2018 6:02 pm

“how some journals conduct peer review”
I don’t think this one does; maybe it goes through the motions. Their business is based on author payments.

John Dowser
Reply to  Javier
January 31, 2018 10:55 pm

It seems you are misinterpreting that graph or the meaning of wavelet analysis representation.
But do carry on.

Peter Sable
January 31, 2018 5:53 pm

Good use of wavelet to get a picture, terrible conclusion from there.
There is one spike of 500 year cycles correlated at the center of ~750 BC in all three signals. That’s it.
And at no other time is there a spike in the 500 year cycle energy on all three waveforms.
I look at the full wavelet analysis in Figure 2 and it looks indistinguishable from pink noise. Those sidebars are what pink noise looks like when you properly window finite series data.
Also, I find the ~200 year cycle more distinguishable than the 500 year cycle. It’s in all 3 series, and happens more often. The averages on Figure 2 show a higher peak for all three at the ~200 year cycle. That actually might be statistically significant. I’d need the raw data source to be sure.
The ONE 500 year peak is not statistically meaningful.
This quote, while I realize it might be a foreign language issue, is a dead giveway:

n this work, the reconstructed sunspot number series in the past are analyzed to research for quasi ~500-year cycle signals

You don’t go LOOKING for a particular signal. You analyze and see what you find. They have the process backwards.

Reply to  Peter Sable
February 1, 2018 3:15 pm

Good use of wavelet to get a picture, terrible conclusion from there.

Spot on! The analysis results in Figure 2 at semi-millennial periods show none of the persistence of power that characterizes truly quasi-periodic, narrow-band processes. The authors’ claims are terribly far-reach “science.”

January 31, 2018 6:30 pm

Why does everyone go looking for strictly periodic cycles? Is there any reason to believe that the sun is some kind of regular oscillator? Yes, there are models of the processes in the sun that are helpful in explaining some solar flares and to a degree the sunspot variations and some magnetic field movements, heat and mass transfers. But there is no reason to believe the sun is any different that the earth’s climate.- a chaotic process possibly with one or more strange attractors that does not behave like a mathematical sine wave. Just as the earth has gone through multiple ice ages, temperate periods including a snowball earth, hot house periods, and ice ages similar to the current one.
I’m glad the Chinese have found one possible clue and they are independent enough that they don’t care that it doesn’t point to CO2, a good thing.

Alan Tomalty
January 31, 2018 10:01 pm

At least they didnt use computer simulations. I agree with above poster that said that he didnt believe in sun cycles. Nonone has yet explained why the sun would not be chaotic and how it could produce cycles. I am more inclined to believe in the planet wobble theories than solar cycles. But one thing does puzzle me though. I believe the Chinese long term plan is to suck the West into sinking their economies by believing in global warming. Therefore this study doesnt fit that agenda. Maybe the above poster is right because of Trump the Chinese may have given up on that plan…………….But somehow I dont buy it. I think the Chinese will milk this as far as it goes. So far it is working well. In Ontario alone companies last year were forced to buy $2 billion worth of carbon credits. I wonder what the world total is now. So in the end I think this is a rogue study that got past the sleeping censors.

January 31, 2018 11:31 pm

In a paper we are submitting to a peer review journal, did make use of the paper:
A.K. Kern, M. Harzhauser, W.E. Piller, O. Mandic, A. Soliman: 2012.
Strong evidence for the influence of solar cycles on a Late Miocene
lake system revealed by biotic and abiotic proxies. Palaeogeography,
Palaeoclimatology, Palaeoecology 329–330 (2012) 124–136

DOI: 10.1016/j.palaeo.2012.02.023

where, e.g in fig.7, a 500 yr peak, within a gray band defined as “unnamed 500yr cycle” is clearly visible.
So I cannot understand what kind of new information could the actual paper have effectively discovered.

Reply to  francozavatti
February 2, 2018 2:18 pm

Due to side-band leakage of the spectral window and record-length effects, the results of periodogram analysis are notoriously unreliable in discerning QUASI-periodic components in random or chaotic data. Instead of Figure 7, the wavelet analysis of Figure 10 in your paper should be used for that purpose. It shows only weak, sporadic evidence for a semi-millennial oscillation.

Peter Sable
Reply to  1sky1
February 3, 2018 5:52 pm

Instead of Figure 7, the wavelet analysis of Figure 10 in your paper should be used for that purpose.

As an old signal processing EE, I strongly agree with this assessment. With the wavelet analysis in Figure 10 the windowing is made obvious. It’s fairly obvious that a proper window was not applied for Figure 7.

Peter Sable
Reply to  francozavatti
February 3, 2018 5:58 pm

I note that you run REDFIT and then ignore its conclusions.
Your REDFIT stops at 600 years. The rest of your analysis should also stop at 600 years.
Which means from Figure Figure 7 the only statistically significant intervals are 88, 151, 209, and 352 years
The 500 and 1000 year peaks are not statistically significant. Remember with RED noise, the low frequencies will have very large but statistically insignificant spikes.
You are fighting Nyquist and nature. You simply need more data…2

Charles G Battig
February 1, 2018 8:16 am

Fred Singer and Denis Avery documented these cycles within cycles over a decade ago:
“Unstoppable Global Warming: Every 1,500 Years is a book about climate change, written by Siegfried Fred Singer and Dennis T. Avery, which asserts that natural changes, and not CO2 emissions, are the cause of Global Warming. Published by Rowman & Littlefield in 2006, the book sold well and was reprinted in an updated edition in 2007.
The title refers to the hypothesis of 1,500-year climate cycles in the Holocene first postulated by Gerard C. Bond, mainly based on petrologic tracers of drift ice in the North Atlantic.[1][2]”

Pamela Gray
Reply to  Charles G Battig
February 3, 2018 7:47 am

What cycles? Solar? Oceanic? Plate tectonics?

February 4, 2018 8:24 am

However you may feel about the significance of a couple of 500 year cycles they are proof positive compared to the thin 150 year slice of history that Global Warming is based on.

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