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Could cosmic rays be causing global warming?

The skeptic argument...

"In 1996 we discovered a surprising influence of the Sun – its impact on Earth’s cloud cover. High-energy accelerated particles coming from exploded stars, the cosmic rays, help to form clouds. By regulating the Earth’s cloud cover, the Sun can turn the temperature up and down. As the Sun’s magnetism doubled in strength during the 20th century, this natural mechanism may be responsible for a large part of global warming seen then." (Henrik Svensmark)

What the science says...

While the link between cosmic rays and cloud cover is yet to be confirmed, more importantly, there has been no correlation between cosmic rays and global temperatures over the last 30 years of global warming.

Cosmic rays may play a part in helping form clouds. If this is the case, increased cosmic rays would lead to more cloud cover, resulting in a cooling effect. Conversely, decreased cosmic rays would warm the earth. To calculate the maximum possible role of cosmic rays in recent warming, global temperatures were compared to cosmic radiation levels measured by neutron monitors at the Earth's surface. While there was good correlation between cosmic radiation and temperature prior to 1970, the correlation breaks down sharply after 1970. The analysis concludes that "between 1970 and 1985 the cosmic ray flux, although still behaving similarly to the temperature, in fact lags it and cannot be the cause of its rise. Thus changes in the cosmic ray flux cannot be responsible for more than 15% of the temperature increase" (Krivova 2003).


Figure 1: Reconstructed cosmic radiation (solid line before 1952) and directly observed cosmic radiation (solid line after 1952) compared to global temperature (dotted line). All curves have been smoothed by an 11 year running mean (Krivova 2003).

Similarly, a comparison of neutron monitor measurements, Beryllium 10 and Carbon 14 isotopes (both proxies for cosmic radiation) with global temperatures found that cosmic rays "have been in the opposite direction to that required to explain the observed rise in global mean temperatures" (Lockwood 2007). Regardless of whether cosmic rays help form clouds, the trend in cosmic radiation is opposite to that required to cause warming.

Breakdown in the correlation between low clouds and cosmic rays

There are other problems proving the causality link between cosmic rays and cloud formation. One of the key proofs of Svensmark's cosmic ray theory is the high correlation between low cloud cover and cosmic rays. However, the correlation broke down in 1991 (Laut 2003). At that point, cloud cover began to lags cosmic ray trends by over 6 months while cloud formation should occur within several days (Yu 2000). The correlation completely breaks down in 1994.


Figure 2: Low cloud cover (blue line) versus cosmic ray intensity (red line) (Laut 2003).

Svensmark explained the 6 month lag as data uncertainty (Svensmark 2003). He also claims the loss of correlation after 1994 is due to long term calibration drift with the ISCCP satellites (Marsh & Svensmark 2001). The ISCCP disagree.

Critique by Sloan and Wolfendale

Another analysis scrutinizes the link between cosmic rays and cloud cover and finds several discrepancies. As cosmic radiation shows greater variation in high latitudes, one would expect larger changes in cloud cover in polar regions. This is not observed. Examining the nuclear reactor accident at Chernobyl, ionization from the radioactivity would be expected to produce an increase in cloud cover. There is no evident increase in cloud cover following the accident (Sloan 2007).

Even if these difficulties can be resolved and the causality link between cosmic rays and cloud formation is proven, this would mean cosmic rays would have been imposing a cooling influence on climate over the last few decades.

Printable Version  |  Link to this page

Further reading

A team of scientists from 17 countries have found the most likely origin of galactic cosmic rays - the centres of distant galaxies (Active Galactic Nuclei) powered by supermassive black holes. This discovery is not particularly pertinent to the global warming debate but it is cool :-)

Comments

Comments 1 to 15:

  1. I always thought this hypothesis seemed unlikely, but...

    What about the last 10 years of global not warming? Why does CO2 get an 800 year wrong direction lag and the sun has to be exactly in step to be a viable hypothesis?
    Response: The point is that because the sun has correlated so closely with temperature in the past, when the correlation ended in the 1970's, it's reasonable to conclude some other forcing imposed itself on the climate. Re the CO2 lag, the ice core records actually confirm the amplifying effect of atmospheric CO2. As for the last 10 years of global not warming, you'll find the warming rate is the same over the last 10 years as over the last 30 years.
  2. Den siste mohikanen at 02:10 AM on 3 January, 2008
    First, the Harrison paper of 2006 state

    "...Furthermore, during sudden transient reductions in cosmic rays (e.g. Forbush events), simultaneous decreases occur in the diffuse fraction, showing that the diffuse radiation changes are unambiguously due to cosmic rays."

    http://www.cosis.net/abstracts/EGU06/07661/EGU06-J-07661.pdf

    Hence, it is pointless to argue that cosmic rays do not affect cloudiness. The correlation is there on a timescale of hours to decades, and as others have shown, on centennial to billion of years. The mechanism might not be what Svensmark has proposed but it doesn't change the basic fact if he is wrong about that.

    Secondly, your argument is nonsensical, as what Svensmark and other argue is not that cosmic rays can account for all climate influences. But if he is right - and evidence is piling up that he is - two things follows.

    1) the parametrisation in current GCMs are wrong as they fit past temperatures without taking this effect in consideration. Hence they are not reliable as tools for forecasts.

    2) climate sensitivity is overestimated by earlier attempts such as Hansens, as one major forcing was not considered when calculating those sensitivity values.

    What "sceptics" such as me claim is that there is precious little evidence to support the higher estimates on future temperatures as presented by UN (IPCC). And quite a bit of evidence against it. Emission scenarios is, well, rather extravagant, as they include projections of emissions many times higher than todays in year 2100 in spite of our likelhood to develop good alternatives to the ever more pricier fossile fuel (current trends are cutting the cost of renewables at half each decade). Climate scenarios based on these extravagant emission scenarios is then calculated with GCMs that are likely overestimating the response to a particular forcing. In general I would say sceptics accept that the climate warms when we add CO2 to the atmosphere, but we believe its effect will be muted by the climate systems rather than enhanced.

    I also want to add that I recognise all other environmental (and geopolitical) problems associated with burning fossile fuel and find that a compelling reason to put higher efforts in developing alternatives.
  3. Den siste mohikanen at 08:03 AM on 14 March, 2008
    Sir, you state that
    "The point is that because the sun has correlated so closely with temperature in the past, when the correlation ended in the 1970's, it's reasonable to conclude some other forcing imposed itself on the climate. Re the CO2 lag, the ice core records actually confirm the amplifying effect of atmospheric CO2. As for the last 10 years of global not warming, you'll find the warming rate is the same over the last 10 years as over the last 30 years."

    For sure, neither the sun nor CO2 nor the two together make up for the only climate forcing. So your argument is a bit weak by itself, but even if we assume that all the unexplained difference is due to CO2, that doesn't give as much room for IPCCs +6°C forecast that you seem to imply.

    If all the difference from Krivova et al graph is attributed to CO2 that means that burning half of our known reserves of oil and gas has yielded us less than 0,3°C in temperature change. Some may be in the pipeline but several degrees? The climatic response time would need to be many hundreds of years for that to be possible, which clearly is not the case with TSI & cosmic ray forcings.

    I would also think that the discussion would be less confusing if we started to define what kind of cosmic rays we are discussing. If I remember correctly Laut is using low energy CR but what Svensmark and others claim is that it is cosmic rays of a certain energy (around 10 GeV) that makes the difference: only these energies create the secondary particles needed for the ionisation over low altitudes far from land. Sometimes the CR of high and low energies follow eachother, other times they won't; hence we should clearly state what kind of cosmic rays we are refering to.
  4. Here are a few new studies in favor of the climate-GCR link:

    http://aps.arxiv.org/ftp/arxiv/papers/0803/0803.2765.pdf

    http://aps.arxiv.org/ftp/arxiv/papers/0803/0803.2766.pdf

    GCRs are certainly a fascinating aspect of climate.
  5. It is suggested that high level cloud formation is not affected because of the differences between ice crystals (high level)and vapour ( low level).
    There is a strong correlation between CR's and low level cloud referred to in this paper...

    http://www.solarstorms.org/CloudCover.html cosmic ray/low cloud cover.

    "The correlation of low cloud factor and cosmic ray flux is unexpected as the maximum degree of ionization by cosmic rays occurs in the altitude range 12-15km, i.e. close to or above the tropopause. The altitude ranges covered by clouds of different type are: 0-3.2 km for the low clouds, 3.2-6.5 km for the mid-level clouds and 6.5-16 km for the high clouds. Thus any cosmic ray induced cloud effect would be expected to be stronger for high rather than low cloud layers (Kernthaler et al. 1999; Jorgensen and Hansen, 2000). An explanation may lie in the fact that, as the neutron detectors are located at ground level, the measured flux is more representative of lower than higher regions of the atmosphere. Also, we suspect that the physical state of the cloud droplets may play a significant role in the cosmic ray-cloud interaction. It has been pointed out before that the physics of ice and liquid clouds may differ (Gierens and Ponater, 1999). By analysing different low cloud types separately we found that clouds in a liquid phase account for almost all the variability during the observed period, leaving the ice clouds constant in time, except at the poles where a slight increasing trend for some of the ice cloud types is found. Thus the greater sensitivity of low cloud to cosmic rays may result from the preponderance of liquid phase cloud types at lower altitudes (less than 6-7 km). "
  6. A thought: cosmic rays are essentially protons, alpha and beta particles (90%,9%,1%) and since it is well known that both alpha and beta particles cause condensation trails in cloud chambers thro' ionisation, does it not follow that in appropriate atmospheric conditions they would cause condensation nuclei to form?
    And that the extent of such formation would depend on the quantity and energy levels of these particles?
    Also, is the ratio of particles always the same or is there variation which would allow for increased/decreased cloud formation regardless of the overall level of CR's?
  7. More recent studies:

    http://www.sciencedaily.com/releases/2008/12/081217075138.htm

    http://www.sciencedaily.com/releases/2009/05/090511122425.htm
  8. George Curzon at 01:25 AM on 30 May, 2009
    The point is how much heat arrives on the surface of the earth for what duration. If you leave water in a pot on the stove, and do with the the heat control a mock-up of the suns behaviour over the past 1100 years, the water will get hottest when you turn the heat up and leave it up.
    The water will not get hot hot when you give irregular bursts of heat, then turn it down again, or no heat.
    That temperatures continue to rise when sunspots level off is analogous to the water continuing to heat when you leave the stove turned on.
    Perhaps a pig on a spit might be a sizzling analogy for some.
    Until our planet reaches the temperature of the surface of the sun as it would be at this solar radius, we are going to continue heating up. Hopefully, sunspots will drop off before then.
    The 'exact' set interacting mechanisms of cloud formation would be interesting to know, and must affect the amount of the suns energy arriving at what the oil-well-country-occupying military types refer to as 'ground zero', eh?
  9. I am sure the global warming denialists are going to climb onto the bandwagon that cosmic rays are found to influence tree ring growth - http://news.bbc.co.uk/earth/hi/earth_news/newsid_8311000/8311373.stm - and then try to tie that to proof that cosmic rays are responsible for climate change.
    What really amuses me about climate change denialists is the fact that they postulate all of these other reasons for climate change, like cosmic rays, water in the atmosphere, and so on, and then state that there is no climate change, or at least that it is not anthropogenic. What a great cop out so that life can continue as normal. And so it goes........
  10. "The bottom line is even if these difficulties can be resolved and the causality link between cosmic rays and cloud formation is proven, all they'll find is the cloud formation 50 years ago is similar to now and has had little to no impact on the last 30 years of long term global warming."

    Not so; as I posted somewhere else on this site there are 2 factors here - cosmic radiation and water vapour. If CR remains essentially the same you can still increase cloud formation if WV concentration increases.
    Temperature rises from CO2 increases are 'amplified' by increased WV according to AGW hypothesis - which is confirmed to be ocurring in the lower troposhere by direct measurement.
    Work by the Danes has shown that CR's act more like a catalyst in that single particles can cause many nucleation events, so the effect becomes SO2/WV dependant if CR level is constant.
    There is a link to the website of the Danish Technical University on the page "Do cosmic rays cause clouds?" (#40)
    "Set loose by cosmic rays passing through the atmosphere, the electrons attach themselves to fragile clusters of sulphuric acid and water molecules. Their electric charges stabilize the clusters while more molecules join them. When the molecular clusters are big enough, the electrons can leave them in a stable state, and go off to encourage other clusters to grow.

    In other words, the electrons act as catalysts, which promote chemical action while remaining unchanged themselves. A single electron can make many attempts to grow clusters, even though it will fail if it leaves too soon. "
  11. Recently I watched a lecture by Dr. Richard Alley, at the AGU (link below). He mentions a "Muschler et al. 2005" paper, with a very neat graph showing a distinct spike in cosmic rays during the Laschamp event some 40 thousand years ago, with no corresponding change in temperature at the same time.

    I could not find the paper, though. Could anyone help?

    (relevant part at 42:10 min)
    http://www.agu.org/meetings/fm09/lectures/lecture_videos/A23A.shtml
  12. Mizimi, it doesn’t matter what the purported mechanism of GCRs’ effect is--water vapor, cloud formation, or anything else.

    Once the changes in GCR level stopped (i.e., GCR level became constant), the resulting energy imbalance of the Earth must “immediately” have started to shrink as the Earth “immediately” started to heat and therefore radiate more to match the new, now constant, level of GCR--regardless of whether the GCR effect occurs via some additional mechanisms involving water vapor, and regardless of whether the higher level of GCR amplifies the effect of increased water vapor.

    But the Earth’s energy imbalance has not been shrinking. It has continued to grow, which means the cause of the imbalance has continued to grow, which means the cause cannot still be GCR, because GCR has been constant for half a century. It is impossible for the effect to lag this long.

    This is the same reason the effect of solar radiance’s increase up to the 1950s cannot lag this long. The same argument applies to any factor once it stops changing.
  13. Possible error in this article...

    I try always to verify quotes from original sources in order to eliminate the possibility of misattribution. In this article, there is a quote referenced from a Max Planck article here: http://www.mps.mpg.de/dokumente/publikationen/solanki/r47.pdf (Krivova 2003).

    The quote is "between 1970 and 1985 the cosmic ray flux, although still behaving similarly to the temperature, in fact lags it and cannot be the cause of its rise. Thus changes in the cosmic ray flux cannot be responsible for more than 15% of the temperature increase".

    The above referenced .pdf file is a scan and is therefore not searchable for this quote. I have attempted to read the entire article (a daunting task for a non-scientist like myself) and cannot locate the referenced quote. A Google search finds only additional references to this .pdf and this article.

    Is the above quote actually in the referenced article? If so, I'm blind and didn't see it. If not, where does this quote come from?
    Response: The quote is on page 281 of that paper, beneath the graph I reference above.
  14. Thanks! I now see the quote (and will have my eyes checked).
  15. Here's the graph I mentioned above about the Laschamp event:

    http://ossfoundation.us/projects/environment/global-warming/myths/images/galactic-cosmic-rays/LaschampAnomaly.jpg/view

    I presume it comes from this paper:

    Muscheler et al. 2005
    "Geomagnetic field intensity during the last 60,000 years based on 10Be and 36Cl from the Summit ice cores and 14C"

    http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VBC-4FTS349-2&_user=10&_coverDate=09%2F30%2F2005&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1188611081&_rerunOrigin=scholar.google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=d7767a216035551c2353da3f1cd38838

    The graph looks pretty strinking to me.

    John, do you think it would be worth adding this to a future update on this argument?

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