"SKY" experiment demonstrates link between cosmic rays and condensation nuclei!

After a long embargo, results from the Danish National Space Center (DNSC) Sky experiment were finally published in the Proceedings of the Royal Society. These results will probably we overshadowed with today's announcement of this years' physics nobel prize winner (for the COBE microwave background experiment), but they are very important nonetheless.

This is the Royal Society's press release on the publication of Svensmark et al.:
“Using a box of air in a Copenhagen lab, physicists trace the growth of clusters of molecules of the kind that build cloud condensation nuclei. These are specks of sulphuric acid on which cloud droplets form. High-energy particles driven through the laboratory ceiling by exploded stars far away in the Galaxy - the cosmic rays - liberate electrons in the air, which help the molecular clusters to form much faster than atmospheric scientists have predicted. That may explain the link proposed by members of the Danish team, between cosmic rays, cloudiness and climate change.”

You can also find more about it in the Danish National Space Center press release

The experiment itself is a 7m3 cloud chamber containing marine like air. By controlling the ionization rate using different UV fluxes (i.e., mimicking different cosmic ray ionizations), the group checked to see whether the growth rate of small condensation nuclei is affected by different ionization rates, and indeed it does as can be seen in the first figure. The experiment itself can be seen in the second figure below.
Results from the Danish National Space Center SKY reaction chamber experiment: Condensation nuclei density as a function of ion density, under steady state with the environmental conditions (including SO2 at 155 p.p.t, H20 at 35% RH and H2SO4 at 108cm-3). Evidently, more ionization implies more particle nucleation.

The Danish National Space Center SKY reaction chamber experiment. The experiment was built with the goal of pinning down the microphysics behind the cosmic ray/cloud cover link found through various empirical correlations - and it was successful! From left to right: Nigel Marsh, Jan Veizer, Henrik Svensmark. Behind the camera: the author.
What do these results imply? For a long while, evidence pointing out towards a Cosmic Ray → Cloud Cover → Temperature link has been accumulating. (e.g., see this short review). The evidence was clear enough to convince many (such as your humble servant) that the Cosmic ray climate link is the only reasonable explanation for the plethora of data. However, a big thorn was the lack of physical evidence for the physical mechanism, which until now was only speculated. Until now that is.

The SKY experiment unequivocally demonstrates that more cosmic rays would imply more condensation nuclei in the atmosphere. In many circumstances, it is reasonable to expect that more of the small condensation nuclei would also imply more of the larger cloud condensation nuclei which form the seeds of clouds. Namely, there would be a link between atmospheric ionization (i.e., cosmic rays flux variations) and climate, in regions devoid of other condensation seeds (such as dust over land).

This link implies that a large fraction of the 20th century global warming can be explained through increased solar activity (which reduced the cosmic ray flux reaching Earth). More about that can be found in this discussion, or in this paper.

Kudos for Henrik Svensmark and his group!



This is fantastic! The question is what happens next? When will this result percolate throughout the scientific community? And more interestingly: when will cosmic rays be included in climate models? I guess only time will tell.

Depends on which part of the scientific community... although the evidence for a cosmic ray influence has been building up for quite a few years, "mainstream" climatologists have been very reluctant to seriously consider it. The reason is of course political, as it would weaken the case for anthropogenic greenhouse gas warming - allowing for natural global warming would imply that the anthropogenic contribution is smaller than often claimed. As for actually incorporating the effects of cosmic rays in climate models, this is still problematic. The reason is that the link is through modulation of the cloud parameters, which even without cosmic rays are the least understood ingredient of global climate models...

You claim that "the reason (for criticizing the cosmic ray - climate hypothesis) is of course political ...". However, are you yourself free of any polical motivation in your research? I can see a lot more political reasons to want to deny or downplay the anthopogenic influence on climate than to exaggerate it. Industry, business and politics (think that they) have much more to gain in downplaying human induced climate change (HICC) than in accepting it. The vested interests that seek to downplay HICC are much more powerful, both politically and economically speaking, than the interest groups that seek to highlight the anthropogenic component of climate change. Who do I trust more to say something sensible about climate change, SHELL or Greenpeace? You may chose the former, though I would opt for the latter. Because SHELL has a much bigger stake in a certain outcome.
You seem heavily branded on downplaying the human influence on climate. You and some others look so hard for correlations to support your preconceived notion that you finally come up with some, but by taking questionable shortcuts according to many others in the field. What political interests have other scientists to criticize your work? Their funding does not depend on downplaying your results. If anything, the more uncertainty in the climate "debate", the more chance for funding. Since your results disagree with the "mainstream" scientific findings, it adds to the perceived uncertainty, so it adds to the chances for funding.

I could much easier imagine a political motivation in your research than in the research of your critics.

A related question I have is to what extent you are responsible for the text in press releases accompanying your articles? In press releases of your work (I think it as SV2003), and also in that of Svensmark (2006), the actual research described in the paper is extrapolated miles away beyond what was studied and a heavy political message is pushed forward that the anthropogenic effect on climate change is much smaller than previously thought. It is all due to the sun, so please, go on with business as usual. (The last part is me reading in between the lines.) Smells like oil to me.

Dear Darrel,

You raise several serious "accusations". Let me address them.

First, you ask "However, are you yourself free of any polical motivation in your research?". The answer is of course yes, I am free from any political motivation. I don't get a cent from any industry organization, nor did I ever get any. My main research (and thus funding) is mainstream astrophysics. Thus, you can rest assure that I have no vested interest nor do I owe anything to anyone.

Regarding your specific question of whether I prefer SHELL or Greenpeace, I choose neither. As a scientist, I am obligated to seek the truth even if it may be unpleasant. I am personally in favor of burning less fossil fuels (because of many reasons other than global warming) and I know that my scientific stand on global warming will not necessarily help that point.

I can also attest that my colleagues whom I know best, including Jan Veizer and Henrik Svensmark don't get industry money. In fact, if any, they had a good motive not to support the views they now hold. Jan Veizer set out to reconstruct the tropical temperature over the past 550 million years because he wanted to find the CO2 fingerprint. Veizer is also more of an environmentalist than most of us. It was a disappointment to him that he couldn't quantify the effect of CO2. Moreover, he actually donates money to keep an environmental science scholarship running. Henrik Svensmark was working in the Danish Meteorological institute at the time he found that cloud cover follows the cosmic ray flux variations. His research made him a persona non-grata at his home institute. If anything, he had a good motive not to pursue that research because as a scientists he simply followed the truth. Neither of course get oil money. So how can you say any of them are politically motivated?

You are correct that on the whole, SHELL has more $'s to lose than an average mainstream climatologist, but it wouldn't mean that a single SHELL employee would fight as harshly as an average climatologist would, since the single climatologist may have more to lose than the particular oil employee. Without the anthropogenic global warming scare, the amount of money going to climate research would have been significantly reduced. So the climate community should fight hard to keep its supply line running.

Also I think of course that you're wrong when you write that "If anything, the more uncertainty in the climate "debate", the more chance for funding. Since your results disagree with the "mainstream" scientific findings, it adds to the perceived uncertainty, so it adds to the chances for funding". There are several reasons. First, because there is no evidence that the global warming is anthropogenic except for the fact that there is supposedly no other explanation, it means that if another explanation does pop up, immediately the stand of anthropogenic GHG warming weakens dramatically.

The second point can be easily demonstrated with the famous quote of Stephan Schneider in Discover magazine (I bring the whole quote so that I will not be accused of placing it out of context):

"On the one hand, as scientists we are ethically bound to the scientific method, in effect promising to tell the truth, the whole truth, and nothing but - which means that we must include all the doubts, the caveats, the ifs, ands, and buts. On the other hand, we are not just scientists but human beings as well. And like most people we'd like to see the world a better place, which in this context translates into our working to reduce the risk of potentially disastrous climatic change. To do that we need to get some broadbased support, to capture the public's imagination. That, of course, entails getting loads of media coverage. So we have to offer up scary scenarios, make simplified, dramatic statements, and make little mention of any doubts we might have. This 'double ethical bind' we frequently find ourselves in cannot be solved by any formula. Each of us has to decide what the right balance is between being effective and being honest. I hope that means being both."

So, clearly, scary scenarios are more advantageous than benign ones.

Anyway, if you "smell oil", perhaps it is because we were told too many times that if someone is against anthropogenic GHG he is "one of them, one of the bad guys". The climate community turned many of us into paranoids. You smell oil everywhere even where there is no drop of it. The difference between us, though, is that my research led me to change my preconceptions, so I am not gullible to the propaganda I hear (and I admit I used to be before stumbling into the field).

As for my claims about global warming over the 20th century, these are not just based on long term climate variations. If you empirically study Earth's climate sensitivity on a wide range of time scales, ranging from the 11year solar cycle to 100's of millions of years, you find that Earth consistently behaved with a low (black-body like) response, not much larger as advocated by the climate community. Take a look here. Thus, my own research leads me to conclude that a large fraction of the warming is natural, and the anthropogenic caused increase by say 2100 will not be larger than say 1 deg C, and I couldn't care less what Shell thinks nor Greenpeace.

I think you and all your cousin Darrels and all the other Darrels of the EcoMarxist fraternity are on the track of all cults. Humiliation.
The US Government alone, you know the Great satan to all Left Wing groups, passes over to the Funding Parasites in excess of $5 billion a year for politically motivated Darrels. Why do you accept the money if it is tainted by Capitalism??
The whole issue is Political, it has only an Environmental platform. It is about Extreme Left wing politics subverting the Industrial Complex as it has developed.
Young, impressionable people are being radicalised into the most dishonest political movement in human history.
All the EcoMarxists have is a chart showing a relationship and an increasingly dodgy one at that.(and a lot of taxpayers money)
The issue of funding also explains a lot about the amount of press given to the Left. They can afford it.
The EU countries are hot on Kyoto because the carbon Tax will go along way to solving their unbelievably large pension and health care shortfall. Unless it is world wide their uncompetitive industries will be wiped out by the Non Kyoto nations. Particularly Asisn nations.
So I suggest you take a hockey stick to you portrait of Al (scary movie 4) Gore and remember that great tennet of the Left about Democracy, the right to dissent etc etc.
Science will win out, not Dodgy relationship charts.

Why is it so important for humans to be the source of Global Warming, politically speaking that is?

Well I read the paper, and suffice it to say there is little relation between the press release and the paper. The paper itself merely shows that aerosols form around ions if you provide a ton of SO2, O3 and UV light. This is well known, and it is even well known that the main source of ions in the lower atmosphere is cosmic rays (about 10^3/cm3)

Under such conditions, the formation of aerosols is limited by the number of condensation nuclei and ions. There was little to no aerosol in the gas entering the cell, which left the ions and the walls of the cell as the only possible nucleation sites. In such a situation, the formation of aerosols depended on the ion density.

If you want a discussion of the photochemistry see Rabett Run which also points to a Mexico City study that shows the limiting factor in that natural atmosphere is the availability of SO2 and, to a lesser extent, NO2 (there is a smoking gun figure from the study at the end of the post). The NO2 is a source of ozone, which plays the same role as the ozone in the smog chamber, but at a much lower concentration.

Eli, natural marine concentration ranges between 10 to 200 p.p.t.v (e.g., Lelieveld et al., Phil. Tran.: Bio. Sci., 352, 149). The graph you see above is taken at 155 p.p.t.v, so obviously, Svensmark et al. did take a value which is within that found in the clean marine environment, i.e., they didn't take Venus type concentrations, nor anything like Mexico city. So it isn't a ton of SO2.

Ion concentration in the lower half of the troposphere ranges between less than 1000 to about 2000 ion pairs / cm3, so the range they cover in the experiment does correspond to terrestrial conditions. So it isn't a ton of ions.

As for the lack of aerosols in the gas entering the cell, isn't it the whole point to see that in regions devoid of natural sources of aerosols (such as dust over land), aerosol growth depends on ion density?

As for SO2 being the bottleneck, it is very likely that under various conditions, it is the bottle neck in aerosol formation and growth. This would explain why the correlation between cloud cover and cosmic rays (ionization rate) is observed to be predominantly with low altitude clouds. Over the clean marine environment, the really low ion concentrations make the ions the bottleneck, while everywhere else, there is either enough ions (e.g., at higher altitudes) to make the SO2 the bottleneck, or there are enough natural sources of aerosols (e.g., dust over land), such that aerosol growth is unimportant.

As I told you in person, you gloss over the fact that climate models, after being "tuned" over a decade or two, do reconstruct the observed climate for the next few decades.
These models are then run foreward 50-100 years and they show the warming of 2-5 degrees.
Many processes may change and influence the parametrizations used, but if anything these changes will probably increase the warming.
Also, non-linear, irreversible, outcomes can cause a catastrophic release of greenhouse gases or warming. So criticizing the models actually points out the opposite - the warming may be much underestimated.
One more thing about paleoclimate CO2. Nobody claims there were ancient civilizations which released CO2 and caused warming. It is agreed that the ice ages over the previous 1E6 years are a result of Milankovich cycles. The CO2 may have amplified the original very small temperature variations and increased them many times.
So, again, this is a cause to worry, not to dismiss worries.

Amnon, first let me begin by writing that that it always was fun having debates with you. It reminds me of debates we had some 15 years ago... (so, was Nixon a good president or not? ;-) )

Anyway, as for science. You are correct that there are numerical models which (sort of) reproduce the global warming observed over the past century. However, as I explain below, it doesn't mean much. In fact, if you look carefully, you will find inconsistencies which should raise an eyebrow.

The graph we discussed in person is one similar to the one in this figure (from the IPCC report). Basically, it shows how typical GCMs can reproduce the observed temperature. However, I took the liberty to show the effect of one uncertainty in the model. If you open the IPCC TAR you will find that the indirect aerosol contribution to the warming is estimated to be anywhere from 0 to -2 W/m2. The depicted calculation used the nominal -1 W/m2, which happens to fit the observations. Since these GCMs typically have a CO2 doubling sensitivity of ΔTx2 ~ 3°C, a 1 W/m2 error can cause a warming (or cooling) uncertainty of 1/4*3°C ~ 0.75 °C at equilibrium. Over a century, the climate still doesn't reach equilibrium so a good guesstimate would be about a 0.5°C uncertainty. As you can see from the plot, this known uncertainty can significantly offset the model predictions by a lot! In other words, the fit should be considered coincidental. All it tells you is that in principle, the warming could be explained as being anthropogenic, but it is no proof whatsoever.

Incidentally, when you take a more careful look, you will realize that even if the indirect aerosol effect was better known and miraculously happened to be the -1 W/m2 taken in climate models (and not 0 or twice larger), then there are still interesting inconsistencies. If you look at the graph, you will note several periods during which the models predict a large temperature decrease, which is not seen in the actual data. The reason for these discrepancies, as Prof. Richard Lindzen pointed, is that if you assume too large a sensitivity in the climate model, you will over estimate the effect of a large volcanic eruption (such as Krakatoa). Namely, the sensitivity should be smaller than the typical ΔTx2 ~ 3°C of the models.


someone at the climatesceptics mailing list pointed out that there is another means of producing ions, namely ice, which in turn among other things is the source of lightning. Obviously the lightning is just the tip of the iceberg, loads of ions are produced by ice that don't result in lightning. The primary argument presented is that this ion production invalidates the assumption of climate models, namely that energy is primarily dissipated through radiation. With the massive mechanical production of ions this is obviously not the case and represents a potential explanation for low climate sensitivity. But another interesting aspect of the argument is that it also goes counter to the claim that ions are the limiting factor in cloud formation, thus, also attacking the cosmic ray-cloud connection. Are you familiar with this line of reasoning? And if so, do you have a response to it?

Onar, let me try me try to succinctly summarize my understanding of the role of ice.

- Ice may certainly play an important role in the formation of thunderstorms, which in essence drive the global electric circuit (the "battery"). The conductivity, however, of the lower troposphere, through which the circuit 'discharges', depends on the background level of ions, which are dominated by cosmic ray ionization.

- The ions formed by thunderstorms are of course not important for cloud nuclei formation chemistry, since they recombine very quickly. (A typical ion in the atmosphere lives 100's of seconds only).

- Perhaps Ice may be a source of some of the atmospheric ionization, however, balloon measurements of the background tropospheric ionization levels clearly reveal the solar cycle modulation of it, pointing out that cosmic ray ionization is the dominant source of ionization.

- Last, given that the cosmic ray cloud cover link is apparent also in the warm low latitude (and low altitude) clouds, clearly implies that non-ice related ionization is important.

no single experiment is unequivocal. It must be replicated by other scientists, then perhaps a hypothesis that is confirmed by others can become a theory.

You are of course correct. This is why an experiment is planned in CERN. Hopefully they will corroborate the results. In any case, this experiment is just one piece of evidence in a growing coherent picture.

I wrote Jan Veiser this evening on the same subject, so I guess I'll ask you too. Given that sulphur gasses react with GCR in the atmosphere, is it possible that Tambora (Dalton Minimum) and Krakatoa (before 20th century high sunspot activity) when there were more GCRs entering the atmosphere, actually amplified the cooling effect? Thus, Pinatubo (while smaller) during high sunspot activity and low GCR, would have cooled the climate even less? So maybe the cooling effects of volcanoes during the LIA are up to par with GCM's then, but not today.

Also, I have a strong hunch that you are still giving too much to greenhouse gas warming, 33 - 50 % still seems too high to me... mainly because I cant find a graph that correlates temperature to CO2 increases any better than a flea on a bull. Are you sure that the ocean is done absorbing this 11,000 year high level of sunlight?

Volcanoes: I am not sure how large of a cross effect there will be, namely, volcanoes with more CRs vs. Volcanoes with less CRs. My hunch is that there won't be a cross effect. The reason is that the volcanic dust in the troposphere sinks relatively fast. Most of their effect is dust in the stratosphere which takes long to clean out. Up there, the CRs are not expected to have any effect.

As for the greenhouse warming, it could very well be less than a third. The only reason I am saying it can be is because my best CR contribution towards global warming is about 2/3s of the 20th century warming, implying that my best guess for the rest (i.e., anthropogenic causes) is 1-2/3s = 1/3...

OOPS! I forgot, you're an astrophysicist not a volcanologist. I read in Svensmark's Cosmoclimatology paper that Jan sent me that the CRs react with SO gases which is the aerosol that volcanoes belch. The reason I asked is because the cooling during the Dalton Minimum seemed stronger than other solar minimums. Of course, Tambora blew in 1815, right in the middle of the Dalton Minimum.

By the way, my kid (that's the Kris in the screen name) is about to finish her global warming paper that she is writing for her Honors Earth Science class. She made mention of your CR effects and even quoted you. I was wondering if you would like to take a look at it and offer your thoughts. She seems to have stumbled onto something that pokes a big hole in anthropogenic warming... and I mean a big hole. It made me laugh actually, something that is so simple and right in front of everyone's faces.

a) I think the crucial question is how much do volcanoes affect the amount of aerosols in the low troposphere, and for how long. In the stratosphere, the aerosols can stay airborne for quite a while (>yr), but in the troposphere, they'll be washed away pretty quickly. So, volcanos are probably affecting climate, but I don't think this mechanism interferes with the CR one.
b) Well, ask her to send it.
-- Nir

Hello Nir,

there is one question dithering me for a long time and I'd be very interested in an answer.
If you look at the steady raising temperature since about 1975, don't you think that aerosol deficit is man-made?
This was the time, when catalysators came up, filtering many useful aerosols. This was the time when first raise in Ozone was apparently.
Later came CFC from old refrigerators being replaced with "green" gas to avoid expansion of the Ozone Hole. Nowadays the speech is of soot filters for cars, and so on.
These all are examples of our "clean and green world" policy, but what (in my opinion) has been forgotten is thereby reducing important aerosols, like SOx and others.
Do you think, this might have a secondary effect to the current system in view of cloud condensation nuclei?

Thanks a lot for an answer

I'm a complete lay person but with a keen interest in the AGW theory. One thing which has me puzzled is the decline in temperature 1940-1970, then the steep rise thereafter.Could the drop in temperature during this period have been caused artificially by our use and testing of Nuclear weapons? I understand the basics of the theory behind cloud formation and understand Carbon14 plays a role (?). Nuclear testing increased the levels of C14 in the atmosphere so surely if the cloud formation theory is correct, this must have had some impact, or am I being incredibly simplistic?
I would appreciate your opinion upon this.
Many thanks

Regarding your C-14 question
1. 14-C behaves exactly the same as 12-C (stable carbon). A 14-CO2 molecule is the same as a 12-CO2 molecule. Both molecules will react and behave in the environment exactly the same. That an atmospheric molecule contains a 14-C atom has no bearing on climate science.
2. A radioactive atom only emits its radiation once, then it becomes a different atom (not counting metastable states). A 14-C atom emits a beta particle then instantaneously the atom becomes a 14-N atom. 14-N is stable, not radioactive. Question: if a carbon-14 atom only emits radiation once, what’s it doing the rest of the time? Answer: Nothing - except acting like carbon, smelling like carbon and going out on dates like carbon likes to do. WHEN a radioactive atom emits its radiation is still a mystery, but if you have twelve 14-C atoms: the odds are that six of the atoms would emit in the first 5,000 year period, only three in the next 5,000 years, and the last three would emit sometime over the next 40,000 years. (Half-life value is rounded in this example)
3. 14-C is created in the atmosphere as the result of cosmic radiation interacting with other atmospheric molecules - every minute of the day, ever since the earth got an atmosphere. As a result, it is in everything containing carbon. You have it in your body - naturally. 14-C created as the result of nuclear weapons is absolutely miniscule compared to the amount found in nature. The amount of naturally occurring 14-C being emitted in the burning of coal and other hydrocarbons also dwarfs any created in nuclear weapon explosions.
4. My really bad joke and stupid way of solving the carbon footprint issue is that we should figure a way to convert all of our carbon emissions to 14-C emissions because eventually all the 14-C would convert to stable nitrogen. (I really am joking, folks)

Or we could ban cat-cons.

"In searching for a new enemy to unite us, we came up with the idea that pollution, the threat of global warming, water shortages, famine and the like would fit the bill ... All these dangers are caused by human intervention and it is only through changed attitudes and behaviour that they can be overcome. The real enemy, then, is humanity itself."

— in The First Global Revolution, pp.104-105 by Alexander King, founder of the Club of Rome and Bertrand Schneider, secretary of the Club of Rome


First Global Revolution is a book...good reading with extraordinary accuracy.

I read a book about this research into cosmic rays and cloud formation and to me it seems pausible. So, we now know something more about what controls cloud cover, but we don't fully understand how much clouds heat the planet, by acting as a blanket, or cool, by reflecting incoming sunlight. Hopefully we will soon.

On another related subject, and in the form of a question: the earths magnetic field has declined approximately 10% over the last 150 years and has shown some major field changes at the surface, such as the South Atlantic Anomaly. Since the magnetoshpere protects us from solar radiation, and radiation from deep space, and we now believe there is a link between ionizing radiation and cloud formation, has there been any research into the relationship between changes in the magnetosphere and climate?