Guest Post by Willis Eschenbach
Normal carbon has six neutrons and six protons, for an atomic weight of twelve. However, there is a slightly different form of carbon which has two extra neutrons. That form of carbon, called carbon-14 or “14C”, has an atomic weight of fourteen. It is known to be formed by the interaction of high-energy cosmic rays with the atmosphere.
Therefore, the production of the carbon isotope 14C goes up and down with the number of cosmic rays.
Thus, other things being equal, the production of 14C could be a proxy for how many cosmic rays are passing through the atmosphere. And the number of cosmic rays striking the earth is regulated by a combination of the magnetic fields of the earth and the sun. When the combined magnetic field is strong, it deflects the cosmic rays away from the earth. When it is weak, more cosmic rays strike the earth.
So let me start, as I prefer to do, with the largest, longest view of the underlying raw data. In this case it is something called the “INTCAL13 Calibration Curve”. It is a record of historical variations in the levels of the carbon isotope 14C.
Figure 1. INTCAL13 calibration curve. The interval between values is five years in the recent part of the record (since 11950 BC). In the middle part of the record, from 23050 BC to 11950 BC values are ten years apart. And in the earliest part, from the beginning to 23050 BC, values are 20 years apart.
The large variations in the curve are said to be from slow changes in the earth’s own geomagnetic field over the millennia. However, our knowledge of geomagnetism millennia ago is not of the finest … given that, it does seem like a possible explanation.
Keep that INTCAL13 calibration curve in mind for a moment, and let me move on to discuss a guest post over at Judith Curry’s often-excellent website, by someone named “Javier”. The post is all about solar cycles. And there’s a new post on WUWT discussing Javier’s solar cycles. These are solar cycles that are two thousand four hundred years long, to be exact. How do they know that? Well, here’s Javier’s money graph.
So the obvious question is … how on earth did they get from the curve shown in Figure 1 to the curve shown in Figure 2? Javier says it is done by “removal of the long-term trend” … but how was that done? I went to the cited work of Clilverd et al. to find out the answer.
First, because the sun and the cosmic rays are negatively correlated, they flip the 14C record over as shown in Figure 3. In this orientation, warmer is at the top of the chart and cooler is at the bottom. That’s just a graphic convenience, no problem.
Then they throw away more than three-quarters of the data, leaving only the chunk since 9600 BC as shown in Figure 4.
Figure 4. Inverted INTCAL13 calibration curve since 9,600 BC.
Following that, they fit a linear trend to the data, and detrend it. Then they subtract out a purported 7,000 year signal of unknown origin. Figure 5 below from Clilverd et al. illustrates the procedure. Note that the upper panel of Figure 5 matches my Figure 4.
I note in passing that although Javier asserts a “correct” cycle length of 2400 years, Clilverd shows a 2300 year cycle. I guess that’s why Javier’s version is “adapted from” … but I digress.
Let me recapitulate the bidding. To get from the inverted 14C record shown in Figure 3 to the record used by Clilverd et al, they have
- thrown away three-quarters of the data,
- removed a purported linear trend of unknown origin from the remainder,
- subtracted a 7000-year cycle of unknown origin , and
- ASSERTED that the remainder represents solar variations with an underlying 2,300 year period …
I suspect that y’all can see the problems in each and every step of that process. First and foremost, why throw away three-quarters of the data? That alone disqualifies the study in my mind. But let us continue listing the difficulties:
Where did the claimed linear trend come from? What justifies removing it? Why use an exactly 7,000 year cycle, and where did it come from? How does one diagnose a 7.000 year cycle when you only have about 12,000 years of data, not even two full cycles? How do they know that the 7,000 year cycle is NOT solar-related and the 2,400 year cycle IS solar-related?
And finally, what evidence do we have that the remainder has anything to do with the sun?
But wait, as they say on the TV ads, there’s more. Let’s set the work of Javier aside entirely and return to the question of cosmic rays, which Javier does not discuss. Remember that the relationship between cosmic rays and the climate is supposed to work as follows:
In times when there are more cosmic rays, the rays cause more cloud nuclei to form. As a result more clouds form (and in addition, more 14C forms) and the world is colder. But in times when there are less cosmic rays (indicated by less 14C), there are less clouds, and thus the world ends up warmer.
And according to that theory, people claim that the final dip in the 2400-year cycle seen in Figures 2 & 5 is the cause of the cold times around the Little Ice Age. Back then it was a couple of degrees cooler than at present. If that theory is correct, this means that a change in ∆14C of about 10 per mil reflects a change in cosmic rays that is enough to cause a global temperature change of 2°C.
Now that all sounds good until you take another look at Figure 3. Let me replot it, and this time I’ll include the 10 per mil change in ∆14C, and hence in cosmic rays, rumored to be responsible for the Little Ice Age.
Figure 6. Inverted INTCAL13 calibration curve. Gray lines show the variation in ∆14C of 10 per mil claimed to be from cosmic rays and said to be responsible for the 2° cooling during Little Ice Age. The large swings are said to be due to changes in the strength of the geomagnetic field.
I reckon you folks can see the difficulty … according to this, about twenty thousand years ago it should have been about 100°C colder than today …
Now, about the only way out of this dilemma is to say that the peak-to-peak swing of about 500 per mil in ∆14C is from some kind of non-cosmic ray variations. You know, like the claimed 7,000 year cycle that was removed in Figure 5 that was ascribed to … hang on, I want to get this right … OK, they said it was from “changes within the carbon system itself”.
(Let me say that I like that particular bit of bafflegab a lot, “changes within the system itself”. Seems like that would cover a host of unpleasant variations in any dataset you might find … but again I digress.)
So to recap: IF the claims are true that the changes in ∆14C shown in Figure 6 reflect changes in cosmic rays and that the changes in cosmic rays result in the claimed changes in temperature, then twenty thousand years ago the earth should have been 100°C cooler. Even if I’m wrong by 100%, it is still saying that it was 50°C cooler back then … didn’t happen.
Since that is not possible, then it seems we must assume that “changes within the system itself” are causing the huge swings in ∆14C.
But if that is the case, then it is more than possible that these unknown changes within the system are also responsible for the smaller swings currently ascribed to variations in cosmic rays.
Anyhow, that’s my cosmic problem with rays. Here I have no problems. It’s two AM, I’m a night owl. There’s been rain for three days, wonderful rain. And there’s still rain in the area, a small cell passing north of us. But the wind has shifted. It was blowing strongly from the south or southwest for the last three days. Now the wind is just a mild breeze, and from the west. There are big gaps in the clouds, and the moon, aah, for the first time in a while the moon is finally showing its face. I can hear the distant hungry grumbling of the surf as it nibbles on the ribs of the coastline some six miles (ten km) away … a good night to be alive here in the redwood forest, with the giant trees standing stark and clear in the pale wash of moonlight, and silvered cumulus drifting across the sky.
Best to everyone,
My Usual Request: Misunderstandings are the bane of the web. Please further understanding by quoting the exact words that you disagree with. That is the only way that we can all be clear about the exact nature of what you object to.
My Other Request: Bald statements that someone doesn’t know what they are doing, even if true, are of little use to anyone. If you think someone is using a wrong method or a wrong dataset, please further everyone’s understanding by demonstrating the right method or by linking to the right dataset.