Geomagnetic Forcing of Earth’s Cloud Cover During 2000-2008?
Guest post by Roy W. Spencer, Ph. D.
I’ll admit to being a skeptic when it comes to other skeptics’ opinions on the potential effects of sunspot activity on climate. Oh, it’s all very possible I suppose, but I’ve always said I’ll start believing it when someone shows a quantitative connection between variations in global cloud cover (not temperature) and geomagnetic activity.
Maybe my skepticism is because I never took astronomy in college. Or, maybe it’s because I can’t see or feel cosmic rays. They sound kind of New Age to me. After all, I can see sunlight, and I can feel infrared radiation…but cosmic rays? Some might say, “Well, Roy, you work with satellite microwave data, and you can see or feel those either!” True, but I DO have a microwave oven in my kitchen…where’s your cosmic ray oven?
Now…where was I? Oh, yeah. So, since I’ve been working with 9 years of global reflected sunlight data from the CERES instrument flying on NASA’s Terra satellite, last night I decided to take a look at some data for myself.
The results, I will admit, are at least a little intriguing.
The following plots show detrended time series of monthly running 5-month averages of (top) CERES reflected shortwave deviations from the average seasonal cycle, and (bottom) monthly running geomagnetic Ap index values from the NOAA Space Weather Prediction Center. As I understand it, the Ap index is believed to be related to the level of cosmic ray activity reaching the Earth. (I will address the reason for detrending below).
Note that there is some similarity between the two plots. If we do a scatterplot of the data (below), we get an average linear relationship of about 0.05 W per sq. meter increase in reflected sunlight per 1 unit decrease in Ap index. This is at least qualitatively consistent with a decrease in solar activity corresponding to an increase in cloud cover.
(I’ve also shown a 2nd order polynomial fit (curved line) in the above plot for those who think they see a nonlinear relationship there.)
But just how big is this linear relationship seen in the above scatterplot? From looking at a 70-year plot of Ap data (originally from David Archibald), we see that the 11-year sunspot cycle modulates the Ap index by at least 10 units. Also, there are fairly routine variations on monthly and seasonal time scales of about 10 Ap units, too (click on image to see full-size):
When the 10 Ap unit variations are multiplied by the 0.05 scale factor, it suggests about a 0.5 W per sq. meter modulation of global reflected sunlight during the 11 year solar cycle (as well as in monthly and yearly variations of geomagnetic activity). I calculate that this is a factor of 10 greater than the change in reflected sunlight that results from the 0.1% modulation of the total solar irradiance during the solar cycle.
At face value, that would mean the geomagnetic modulation of cloudiness has about 10 times the effect on the amount of sunlight absorbed by the Earth as does the solar cycle’s direct modulation of the sun’s output. It also rivals the level of forcing due to anthropogenic greenhouse gas emissions, but with way more variability from year to year and decade to decade. (Can anyone say, “natural climate variability”?)
Now, returning to the detrending of the data. The trend relationship between CERES reflected sunlight and the Ap index is of the opposite sign to that seen above. This suggests that the trend in geomagnetic activity during 2000-2008 can not explain the trend in global reflected sunlight over the same period of time. However, the ratio of the trends is very small: +0.004 Watts per sq. meter per unit Ap index, rather than -0.045. So, one can always claim that some other natural change in cloud cover is overpowering the geomagnetic modulation of cloudiness. With all kinds of climate forcings all mingled in together, it would be reasonable to expect a certain signal to emerge more clearly during some periods, and less clearly during other periods.
I also did lag correlation plots of the data (not shown), and there is no obvious lag in the correlation relationship.
All of this, of course, assumes that the observed relationship during 2000-2008 is not just by chance. There is considerable autocorrelation in the reflected sunlight and geomagnetic data, which I have made even worse by computing monthly running 5-month averages (the correlation strengths increased with averaging time). So, there are relatively few degrees of freedom in the data collected during 2000-2008, which increases the probability of getting a spurious relationship just by chance.
All of the above was done in a few hours, so it is far from definitive. But it IS enough for me to keep an open mind on the subject of solar activity affecting climate variations. As usual, I’m just poking around in the data and trying to learn something…while also stirring up some discussion (to be enjoyed on other blogs) along the way.
UPDATE (12:30 p.m. 10 December 2009)
There is a question on how other solar indices compare to the CERES reflected sunlight measurements. The following lag correlation chart shows a few of them. I’m open to suggestions on what any of it might mean.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Leif Svalgaard (14:17:06) :
Isn’t the pressure at the surface simply the weight of all the overlying molecules which wouldn’t change?
It is a dynamic system. I don’t think the association of low barometric pressure with storm fronts is in any way contentious. Am I misreading your meaning?
Sorry, I should have entered a question at the end about how that theory might have an effect on our geomagnetic field and our climate. I’m not trying to hijack anything.
I watched Jasper Kirby and we need a magnetic cosmic ray shield to keep us from spiraling into another ice age. CO2 is not the cause of global warming which gets humans off the hook at least as to Carbon. Aerosols may be the problem but this is so technical you can’t get political types to latch onto something so small.
Jasper needs to speak up in the scientific community that CO2 is obviously not the problem. Everyone should watch the video but it is an hour long.
http://cdsweb.cern.ch/record/1181073
David Radioboy (13:39:06) : “If sunspot activity has such demonstrably dramatic affects on the upper atmosphere, it is a racing certainty that it affects the twelve miles or so of the lower atmosphere that controls our weather.”
Nah. The lower atmosphere isn’t ionized, David. Keep thinking, though.
Dr Spencer, all;
My degree is in archaeology, i xpercialized in obsidian hydration dating, which is an entirely temperature dependent phenomenon. Ergo, I had to study past temperatures, and my own research confirmed the Little Ice
Age and the medieval warm period, so when I first saw the Hockey Stick I was immediately prejudiced against it. Nothing I have seen since has changed my mind.
My willingness to believe Svensmark’s model also comes from archaeology. The principal dating method used is C14, an isiotope of carbon with a half life of about 5600 years crasted in the atmosphere by cosmic ray bombardment, something that has been known since about 1950. Also known is that certain eras have to have their C14 dates “calibrated” using tree ring dating, because in certain periods there was much more C14 produced (obviosly by an increased cosmic ray flux.) Theswe coincide with tghe little ice age and other colder periods.
Correlation is not causation , but when correlations follow a predictable patern it’s certainly worth while to look for a cause, and I find Svensmark’s, Shaviv’s and Veiner;s hnypothesis convincing.
Of course, I;’m only an archaeologist, and not a “climate scientist.”
I also have recently developed arthritis and my touch typing has gotten miserable.
Bart (14:40:21) :
“Isn’t the pressure at the surface simply the weight of all the overlying molecules which wouldn’t change?”
It is a dynamic system. I don’t think the association of low barometric pressure with storm fronts is in any way contentious. Am I misreading your meaning?
The pressure is the weight of all the molecules from the surface all the way up to the ‘top of the atmosphere’. Right?
Expanding the atmosphere a bit does not change the number or total weight of the atmosphere [ignoring a small decrease in gravity with altitude], so the pressure would not depend on the atmosphere breathing.
After the interplanetary geomagnetic index (Ap) is homogenized to correct for the step function in Oct 2005 the current value is no longer unprecedented. The science is settled.
http://img513.imageshack.us/img513/1096/apnoaadec2009.png
ShrNfr (11:26:47) : “Actually, you can “see” cosmic rays (or rather their byproducts) when you are the ISS. When a muon goes through the right area of your skull it causes a flash of light in you visible field.”
OT, but as a word of caution, those flashes could also indicate a torn or about to be torn retina. Been there, done that. If they persist have it checked.
>Bart (13:14:21) :
>
>OK, one thing is, my familiarity with the bulge is a good bit higher than the >stratosphere. But, the higher the clouds, as I understand it, the more they >induce net warming.
I, too, expect to get pummeled for dabbling in things I am not trained in…BUT… I have had the same idea.
I have the idea that when there is a bulged area of clear atmosphere, it is like a thick comforter on a sleeping person–it promotes more warmth. By the same token, a reversed situation, where the clear part of the atmosphere is thinner, that will lead to the cold of space being closer to the surface of the earth…leading to more cold, like a sleeping person covered only by a thin sheet.
Didn’t they say last December that the ionosphere was not where they expected it to be? Wasn’t it 400 meters lower than they expected to find it? How thoroughly do we track its height?
One of the observations I have seen from published papers is that there is a lot of noise when the AP index is between about 10-16. We see it here again in this data. Nothing clear. However when its above 18 the earth trends towards more warming. It maybe that there is in fact an AP index threshold of 18 required before there is appreciable reductions in cosmic rays reaching the lower atmosphere. I personally think there could by chance be a profound simplicity to climate change. It appears we only get appreciable effects when the AP index moves above 18. You can see it in this paper.
Can we use the aa geomagnetic activity index to predict partially the variability in global mean temperatures?M.A. El-Borie1 and S.S. Al-Thoyaib2 International Journal of Physical Sciences Vol. 1 (2), pp. 067-074, October, 2006. It may be we could consider the effects of the AP index like a variable fan beside a cooking pot. It takes an appreciable change to start to have a trend towards warming or cooling of the pot ( I work on cooking issues in addition to work as an agroecologist/climate change scientist). Beans won’t cook in a warming pot unless a threshold temperature is reached and cosmic rays may not be knocked away reliably unless the AP index gets above 18.
Maybe i should have used the analogy of a variable fan on a grain cleaner and that would have been even simpler.
…”so the pressure would not depend on the atmosphere breathing.”
Have you confused me with another poster? I’m not even sure what “breathing” in this context means. There is no doubt whatsoever that atmospheric pressure varies at the surface, and that low pressure there brings on clouds. But, I’m not making any point with regard to low level clouds anyway. I’m merely saying that:
1) I know lower pressure at the surface is associated with cloud formation
2) Perhaps lower pressure in the upper atmosphere could therefore stoke cloud formation there
What I know about that is, at high altitudes, the the so-called diurnal bulge expands significantly when the Sun is active. If gets a lot denser at orbital altitudes, but that is only because it gets pushed up that high where it wasn’t before. Since there is more atmosphere at higher altitude, I would expect the pressure to drop at slightly lower altitude, hence perhaps creating high altitude clouds.
Thus, in a Sun active phase, you could get more high altitude clouds, which would let sunlight through but reflect radiation from the Earth back down, leading to elevated temperature. In a low activity phase, you would get less high cloud cover, resulting in less reflected energy back down, thus enhancing the cooling effect of diminished energy flux. That is the conjecture I am placing forward for review.
Wow – someone on CNN just referred to Global Warming as “weird science that they’ve manufactured” as the last word of a discussion about Sarah Palin trying to become the Anti-Gore
JonesII
Thanks. For further details see: NASA on Galactic Cosmic Rays
Galactic Cosmic Rays also cause ionization. e.g.
The galactic cosmic ray ionization rate, A Dalgarno – Proceedings of the National Academy of Sciences, 2006
Cosmic ray induced ionization in the atmosphere: Full modeling and practical applications Ilya G. Usoskin and Gennady A. Kovaltsov, JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, D21206, doi:10.1029/2006JD007150, 2006
Latitudinal dependence of low cloud amount on cosmic ray induced ionization I.G. Usoskin, N.Marsh, G.A. Kovaltsov, K.Mursula, O.G. Gladysheva, arXiv:physics/0407066v1 [physics.ao-ph] etc.
Bart (15:31:59) :
What I know about that is, at high altitudes, the the so-called diurnal bulge expands significantly when the Sun is active. If gets a lot denser at orbital altitudes, but that is only because it gets pushed up that high where it wasn’t before. Since there is more atmosphere at higher altitude, I would expect the pressure to drop at slightly lower altitude, hence perhaps creating high altitude clouds.
The diurnal bulge is a global [ok, semi-global] phenomenon. You are saying that the combined weight of two unequal sacks stacked on top of each other is different when the heavy sack is on top rather than the lighter one?
Jack Green (14:43:39) : I watched Jasper Kirby and we need a magnetic cosmic ray shield to keep us from spiraling into another ice age.
Agreed. You mean a kind of reflective dome shield like this
http://www.meteo.psu.edu/~mann/Mann/home/mann_treering.jpg
…of course it would need to be launched into space to have the most effect.
Roy
Per comment above on looking at the poles, see Figure 3 in:
Latitudinal dependence of low cloud amount on cosmic ray induced ionization I.G. Usoskin et al 2006. They show about 5 times greater intensity at the poles at a solar minimum than at the equator.
The present solar cycle 23 to 24 is unusually low, so the pole to equator difference may currently be even greater.
Note also Svensmark’s cloud impact being a maximum 7-10 days after a Forbush event. See: Cosmic ray decreases affect atmospheric aerosols and clouds H Svensmark, T Bondo, J Svensmark – Geophysical Research Letters, 2009
Thus comparing the ratio of clouds or reflectivity at 7 days after a Forbush event minimum to the day before one, at the magnetic poles compared to at the magnetic equator, may provide interesting five fold difference in the expected signal, compared to at the solar maximum.
Russian astrophysicists have discovered that the size of the sun varies.
They have constructed a complicated device that can more precisely
measure the suns changing size. It is to be attached to the space station in 2012, and after six years of data sampling they hope to find data which can explain the sun´s size variability to possibly have some connexion with earth´s climate variability But what mechanisms? Very thrilling, but longstanding wait, Alas.
I would like to hear or read more on this topic.
Anyone with more informations?
Jensen
Leif Svalgaard (15:56:12) :
It appears to me you think I am arguing something I am not.
I am not arguing about the surface. I am not conceding anything, but I want you to forget about the surface pressure.
I am arguing that the diurnal bulge increases the volume of the upper atmosphere, more than it increases temperature, and since pressure is inversely proportional to volume divided by temperature in an ideal gas (PV=nRT and all that), I am guessing that the pressure in the upper atmosphere most likely decreases.
My focus is entirely on the upper atmosphere, OK?
In particular, I am not arguing that the diurnal bulge has any effect on surface pressure.
I was merely using surface cloud formation phenomena to extrapolate behavior to the upper atmosphere. But, I can see that only confused the issue.
I am only interested in the upper atmosphere from here on out.
Here is a comparison using many different aspects of magnetism and comparing it to temperature variability.
http://www.appinsys.com/GlobalWarming/EarthMagneticField.htm
And, I am suggesting that lower pressure in the upper atmosphere should lead to cloud formation there.
Leif Svalgaard: (14:17:06)
“If it increases the rate of energy loss to space during a period of more turbulent solar activity then it would have an effect on climate.
What energy loss?
Reply:
The energy loss described in my link:
“Sunspots unleash solar flares that create a ripple effect well beyond Earth. But when that energy flow does reach Earth, the atmosphere reciprocates by ejecting radiation as a cooling effect.”
I take that as meaning a net cooling effect i.e. the cooling exceeds the energy value added by the very tiny increase in solar power. Rather like the way increased windspeed over a mobile fluid takes away energy faster due to the wind pressure creating waves that increase surface area.
Leif Svalgaard:
“Also, if the Earth’s warms, its energy loss to space will increase correspondingly.”
Reply:
Of course it does but you keep saying that the variation in solar power is too small to account for observed temperature variations so the Earth warming is not the cause of the increased rate of energy loss to space. It has instead to be caused by the extra turbulence of the energy flow impacting the upper atmosphere and causing disturbances that increase the surface area of all the layers down to the top of the stratosphere.
Roy Spencer (10:19:43) : writes about cloud chamber particle tracks:
“sounds like a cool experiment, Jeff. But how do you know they are not pixie contrails?”
Until a few weeks ago I would have said the science was settled [heh], so my first question is how much of that “settled science” was done by CRU. The second question would be whether the people who peer reviewed the cosmic ray research excluded those scientists advocating a Pixie Dust Theory. I did find an article [PIXIE DUST: THE SILICATE FEATURES IN THE DIFFUSE INTERSTELLAR MEDIUM] on interstellar pixie dust, but it referred to silicates as opposed to ionized particles.
Given the current state of science, I’ll hedge and say I lean towards cosmic rays being responsible, and agnostic about pixie dust as I’m not an expert in that field.
Jeff