Tag Archives: clouds

ConCERN Trolling on Cosmic Rays, Clouds, and Climate Change

Image courtesy of Flickr user “Mr DeJerk”, used under Creative Commons

OR: Nope, cosmic rays still not driving climate change, cont’d, cont’d…

Clouded “Reporting”

Depending on where you get your science news, you might be hearing claims to the effect that CLOUD at CERN has “proven that cosmic rays drive climate change”, or something to that effect. That’s certainly the impression that climate “skeptics” would like you to get. Unfortunately for “skeptics” (and if we don’t rein in greenhouse emissions, everyone else), it’s not true. While cosmic rays may have some influence on cloud formation, they are not responsible for the present, human-driven climatic change or alleged changes in the geologic past.

What’s the deal?

Although seemingly out of fashion for a while until recently, the “cosmic rays are driving climate” myth has long been one of the mainstays of the self-contradictory climate “skeptic” argument stable, and it’s something covered fairly often at this blog (previous posts here, here, here, here, here, and here). And as with any good falsehood, it starts with a kernel of truth.

It is completely accepted in mainstream science that galactic cosmic rays (GCRs) might be able to influence the nucleation process of potential cloud condensation nuclei (CCN), and that it’s conceivable that this could influence cloud behavior at some level. As the IPCC AR4 noted (I’ll include the full text at the end, after the jump):

By altering the population of CCN and hence microphysical cloud properties (droplet number and concentration), cosmic rays may also induce processes analogous to the indirect effect of tropospheric aerosols. The presence of ions, such as produced by cosmic rays, is recognised as influencing several microphysical mechanisms (Harrison and Carslaw, 2003). Aerosols may nucleate preferentially on atmospheric cluster ions. In the case of low gas-phase sulphuric acid concentrations, ion-induced nucleation may dominate over binary sulphuric acid-water nucleation.

While a plausible mechanism exists, real world verifications are necessarily difficult to undertake. The CLOUD project at CERN is seeking to do exactly that. The “skeptic” and right wing blogospheres are abuzz because Jasper Kirkby, et al. have just published the first results in Nature (Kirkby 2011).

RealClimate has a good rundown of what Kirkby et al.’s results do and do not mean. The short version is that Kirkby et al. do find increased aerosol nucleation under increased ionization (i.e. “more cosmic rays”), particularly in the mid-troposphere, but the effect is smaller at warmer, lower levels where the cosmic ray-climate myth proponents claim it has its greatest climatic effect. Lead author Jasper Kirkby has tried to set the record straight, stating (all following emphases mine):

[The paper] actually says nothing about a possible cosmic-ray effect on clouds and climate, but it’s a very important first step.

While their results provide some confirmation of the potential mechanism by which GCRs might induce cloud nucleation, they in no way demonstrate that GCRs do significantly promote cloud formation in the real world, let alone support the myth that GCRs drive significant climatic change.

“But wait!” I’m sure some of you may be thinking, “the Kirkby et al. results certainly don’t disprove GCRs drive significant climatic changes.” And that’s true enough.

How Do We Know That Cosmic Rays Aren’t Driving Significant Climatic Change?

In reference to the present anthropogenic climatic changes that we’re driving through alteration of the planetary energy balance notably through greenhouse gas emissions, we can theorize what certain “fingerprints” of enhanced greenhouse warming should look like, and examine observational data to see whether those fingerprints show up. And they do.

Moreover, we can examine the claims made by Svensmark, Shaviv, and others who proclaim GCRs drive climate and see whether or not they hold up. They don’t:

We can look at the paleoclimatic record during periods of significant changes in GCR activity, and there is no corresponding change in climate, e.g. the Laschamp excursion ~40kya (Muscheler 2005).

We can examine the change in GCRs in response to solar variability over recent decades or the course of a solar cycle, and find there is no or little corresponding change in climate (Lockwood 2007, Lockwood 2008, Kulmala 2010).

We can look at alleged correlations between GCRs and climate in the geologic past due to our sun passing through galactic spiral arms, and find that these “correlations” were based on an unrealistic, overly-simplified model of spiral structure and are not valid (Overholt 2009). Standard climatic processes (like CO2) more parsimoniously explained the climatic changes even before taking the flawed spiral model into account (Rahmstorf 2004).

We can examine the specific mechanisms by which Svensmark and others have claimed GCRs influence climate via cloud behavior and show that alleged correlations between GCRs and clouds were incorrectly calculated or insufficiently large, proposed mechanisms (e.g. Forbush decreases) are too short lived, too small in magnitude, or otherwise incapable of altering cloud behavior on a large enough scale to drive significant climatic change (Sloan 2008, Erlykin 2009, Erlykin 2009a, Pierce 2009, Calogovic 2010, Snow-Kropla 2011, Erlykin 2011).

Basically, what’s actually been demonstrated by Kirkby, et al. isn’t at odds with the IPCC. What is at odds with the IPCC hasn’t been demonstrated by Kirkby, et al. And the claims by Svensmark, Shaviv, and other ‘GCRs drive climate’ proponents have been debunked at pretty much every step of the way. GCRs may have some influence on cloud behavior, but they’re not responsible for significant climatic changes now or in the geologic past.

To Be Continued?

The CLOUD project at CERN is essentially just getting started. Its preliminary findings will help aerosol modelers, and hopefully it will continue to provide useful results. After the initial furor of “skeptic” blog-spinning dies down, cosmic rays will probably find themselves falling out of favor once again. But there’s no such thing as too debunked when it comes to myths about climate change, and there’s little chance this will be the last time cosmic rays will be trotted out to claim that we don’t need to reduce greenhouse gas emissions.


  • Calogovic, J., et al. (2010): Sudden cosmic ray decreases: No change of global cloud cover. Geophysical Research Letters, 37, L03802, doi:10.1029/2009GL041327.
  • Erlykin, A.D., et al (2009): Solar activity and the mean global temperature. Environmental Research Letters, 4, 014006, doi:10.1088/1748-9326/4/1/014006.
  • Erlykin, A.D., et al (2009a): On the correlation between cosmic ray intensity and cloud cover. Journal of Atmospheric and Solar-Terrestrial Physics, 71, 17-18, 1794-1806, doi:10.1016/j.jastp.2009.06.012.
  • Erlykin, A.D., and A.W. Wolfendale (2011): Cosmic ray effects on cloud cover and their relevance to climate change. Journal of Atmospheric and Solar-Terrestrial Physics, 73, 13, 1681-1686, doi:10.1016/j.jastp.2011.03.001.
  • Kirkby, J., et al. (2011): Role of sulphuric acid, ammonia and galactic cosmic rays in atmospheric aerosol nucleation. Nature, 476, 429–433, doi:10.1038/nature10343.
  • Kulmala, M., et al. (2010): Atmospheric data over a solar cycle: no connection between galactic cosmic rays and new particle formation. Atmospheric Chemistry and Physics, 10, 1885-1898, doi:10.5194/acp-10-1885-2010.
  • Lockwood, M., and C. Fröhlich (2007): Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature. Proceedings of the Royal Society: A. 463, 2447- 2460, doi:10.1098/rspa.2007.1880.
  • Lockwood, M., and C. Fröhlich (2008): Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature. II. Different reconstructions of the total solar irradiance variation and dependence on response time scale. Proceedings of the Royal Society: A, 464, 1367-1385, doi:10.1098/rspa.2007.0347.
  • Muscheler, R., et al. (2005): Geomagnetic field intensity during the last 60,000 years based on 10Be and 36Cl from the Summit ice cores and 14C. Quaternary Science Reviews, 24, 16-17, 1849-1860, doi:10.1016/j.quascirev.2005.01.012.
  • Overholt, A.C., et al. (2009): Testing the link between terrestrial climate change and galactic spiral arm transit. The Astrophysical Journal Letters, 705, 2, L101, doi:10.1088/0004-637X/705/2/L101.
  • Pierce, J.R., and P.J. Adams (2009): Can cosmic rays affect cloud condensation nuclei by altering new particle formation rates? Geophysical Research Letters, 36, L09820, doi:10.1029/2009GL037946.
  • Rahmstorf, S., et al. (2004): Cosmic Rays, Carbon Dioxide, and Climate. Eos Transactions AGU, 85(4), doi:10.1029/2004EO040002.
  • Sloan, T., and A.W. Wolfendale (2008): Testing the proposed causal link between cosmic rays and cloud cover. Environmental Research Letters, 3, 024001, doi:10.1088/1748-9326/3/2/024001.
  • Snow-Kropla, E.J., et al. (2011): Cosmic rays, aerosol formation and cloud-condensation nuclei: sensitivities to model uncertainties. Atmospheric Chemistry and Physics, 11, 4001-4013, doi:10.5194/acp-11-4001-2011.

[Ed.'s Note: This post has been lightly edited since publication for grammar, style, and the addition of relevant references.]

The full text from the IPCC AR4 section on cosmic rays and climate:

When solar activity is high, the more complex magnetic configuration of the heliosphere reduces the flux of galactic cosmic rays in the Earth’s atmosphere. Various scenarios have been proposed whereby solar-induced galactic cosmic ray fluctuations might influence climate (as surveyed by Gray et al., 2005). Carslaw et al. (2002) suggested that since the plasma produced by cosmic ray ionization in the troposphere is part of an electric circuit that extends from the Earth’s surface to the ionosphere, cosmic rays may affect thunderstorm electrification. By altering the population of CCN and hence microphysical cloud properties (droplet number and concentration), cosmic rays may also induce processes analogous to the indirect effect of tropospheric aerosols. The presence of ions, such as produced by cosmic rays, is recognised as influencing several microphysical mechanisms (Harrison and Carslaw, 2003). Aerosols may nucleate preferentially on atmospheric cluster ions. In the case of low gas-phase sulphuric acid concentrations, ion-induced nucleation may dominate over binary sulphuric acid-water nucleation. In addition, increased ion nucleation and increased scavenging rates of aerosols in turbulent regions around clouds seem likely. Because of the difficulty in tracking the influence of one particular modification brought about by ions through the long chain of complex interacting processes, quantitative estimates of galactic cosmic-ray induced changes in aerosol and cloud formation have not been reached.

Many empirical associations have been reported between globally averaged low-level cloud cover and cosmic ray fluxes (e.g., Marsh and Svensmark, 2000a,b). Hypothesised to result from changing ionization of the atmosphere from solar-modulated cosmic ray fluxes, an empirical association of cloud cover variations during 1984 to 1990 and the solar cycle remains controversial because of uncertainties about the reality of the decadal signal itself, the phasing or anti-phasing with solar activity, and its separate dependence for low, middle and high clouds. In particular, the cosmic ray time series does not correspond to global total cloud cover after 1991 or to global low-level cloud cover after 1994 (Kristjánsson and Kristiansen, 2000; Sun and Bradley, 2002) without unproven de-trending (Usoskin et al., 2004). Furthermore, the correlation is significant with low-level cloud cover based only on infrared (not visible) detection. Nor do multi-decadal (1952 to 1997) time series of cloud cover from ship synoptic reports exhibit a relationship to cosmic ray flux. However, there appears to be a small but statistically significant positive correlation between cloud over the UK and galactic cosmic ray flux during 1951 to 2000 (Harrison and Stephenson, 2006). Contrarily, cloud cover anomalies from 1900 to 1987 over the USA do have a signal at 11 years that is anti-phased with the galactic cosmic ray flux (Udelhofen and Cess, 2001). Because the mechanisms are uncertain, the apparent relationship between solar variability and cloud cover has been interpreted to result not only from changing cosmic ray fluxes modulated by solar activity in the heliosphere (Usoskin et al., 2004) and solar-induced changes in ozone (Udelhofen and Cess, 2001), but also from sea surface temperatures altered directly by changing total solar irradiance (Kristjánsson et al., 2002) and by internal variability due to the El Niño-Southern Oscillation (Kernthaler et al., 1999). In reality, different direct and indirect physical processes (such as those described in Section 9.2) may operate simultaneously.

It’s 2010 and cosmic rays still aren’t driving climate change

I hope everyone had a nice holiday season, for those to whom that might apply. Although for many it’s the start of a new year, I’ve got some decidedly not new “news”: cosmic rays aren’t causing global warming and climatic change. Previous studies debunking this meme discussed here, here, here, here, and here.

Yes, it’s probably true that most sane people and even many denialists are no longer trafficking in this particular myth. However, among the fever swamps of the denialosphere and their political allies, this canard remains predictably popular and the idea still garners an inexplicable amount of attention in some physics circles (e.g. arXiv).

Henrik and Jacob Svensmark’s last paper claimed to find a reduction in cloud water content after Forbush decreases (essentially a reduction in cosmic rays hitting Earth during solar flares), and asserted that they had established a global link between cosmic ray activity and climate. Basically, the Svensmarks propose that cosmic rays “seed” cloud cover via ionization, which in turn reduces (increases) the amount of incoming solar radiation received by the Earth, cooling (warming) the climate.  Like so many prior incarnations of the cosmic ray idea, the only problem is that reality completely fails to conform to the hypothesis.

Others have pointed out that the Svensmark selection criteria for the Forbush decrease seemed, shall we say,  “in need of further explanation”. Now Calogovic et al. have  a paper in press [doi:10.1029/2009GL041327] at GRL entitled “Sudden Cosmic Ray Decreases: No Change of Global Cloud Cover” in which they explore this and other problems with Svensmark 2009′s ostensible results.

From the abstract (all following emphases mine):

Currently a cosmic ray cloud connection (CRC) hypothesis is subject of an intense controversial debate. It postulates that galactic cosmic rays (GCR) intruding the Earth’s atmosphere influence cloud cover. If correct it would have important consequences for our understanding of climate driving processes. Here we report on an alternative and stringent test of the CRC-hypothesis by searching for a possible influence of sudden GCR decreases (so-called Forbush decreases) on clouds. We find no response of global cloud cover to Forbush decreases at any altitude and latitude.


In a recent study Svensmark et. al.[2009] analyzed 26 Forbush decreases and, contrary to us, found a significant response in cloud cover and aerosol content. However, a closer inspection of Svensmark’s list of used Fd events revealed 5 Fd events which did not fulfill our selection criteria. For example, the third strongest Fd event in Svensmark’s list which occurred on January 20, 2005 was accompanied by one of the strongest solar proton events. Mironova et al. [2008] analyzed this event and found a significant increases in the aerosol content for the Antartic region. Without further discussion we would like to state that a study as the one by Svensmark et al. [2009] including Fd events which are associated with the solar proton events leads easily to questionable or even contradictory results (see also [Laken et al., 2009]).

The paper concludes:

All our tests did not provide any evidence for a response of the cloud cover to Fd events: 1. No significant global average correlation (Pavg) nor median maxima were found in independent analysis of every Fd event for all cloud layers (not shown). The geographical locations where the cloud cover correlates more positively with the CR intensity are different for each single Fd event, an indication of stochastic correlations. 2. Median values calculated for the frequency distributions of the correlation coefficients are all almost zero and independent of the lag time (not shown). 3. There are no indications for regional effects of CR changes on cloud cover. Pavg and median values obtained in the analysis of grid cells corresponding to particular geographical regions (high and low latitudes, grid cells over oceans and land, see details in AM) show no considerable difference in significance. In conclusion, our global and regional analysis does not indicate any significant response of the cloud cover to undisturbed Forbush decreases.

You’d think that at a certain point, the Svensmarks would just acknowledge defeat and move on. I have a feeling, though, that we’ll be assured that the cosmic ray-climate idea still has some bite to it.

Continents revealed by cloud cover

Cloud fraction data collected by MODIS on NASA’s Terra satellite. Colors range from blue (no clouds) to white (totally cloudy).

Click to massively embiggen

The highest contrast occurs where the difference between moist ocean and very dry areas of land is greatest. Unsurprisingly South America’s Atacama, with its perfect storm of dry conditions, stands out immediately. As does Oz.

Read more at Earth Observatory’s Image of the Day.

[h/t NOVA Geoblog]

Provisional evidence for positive cloud feedback

Clouds represent one of the largest areas of uncertainty in climate modeling and sensitivity and thus one of the last refuges of the deniers. This is especially true of the ones that still manage to garner respect/attention from serious journalists (e.g. Dick Lindzen, Freeman Dyson, and to a lesser extent- in terms of credibility, not overall obsession with clouds- Roy Spencer), but is also rampant in the fever swamps home to common internet denialists. The claims vary but inevitably reduce to the idea that positive forcings will engage one or more negative feedbacks relating to cloud cover. Although the effect is always assumed to be global, the “evidence” offered, such as it is, comes pretty much exclusively from the lower latitudes.

Of course there are several obvious, immediate problems with the existence of such negative feedback(s). As with any claim of low climate sensitivity, it ignores empirical evidence that our climate is fully capable of 5-6°C global changes in both (warming and cooling) directions. Continue reading

Sky remains blue, water still wet

Image courtesy of flickr user eye d

Cosmic rays still not driving global warming. Via Climate Ark:

In research published in Geophysical Research Letters, and highlighted in the May 1 edition of Science, Adams and Pierce report the first atmospheric simulations of changes in atmospheric ions and particle formation resulting from variations in the sun and cosmic rays. They find that changes in the concentration of particles that affect clouds are 100 times too small to affect the climate.

I’ve not read the GRL paper, but here’s the blurb in Science. Previous posts on the cosmic ray myth here and here.

Of moles and whacking: “Global warming is caused by cosmic rays”

The denialosphere is a desperate sort of place. In it, you’ll hear whoppers like “humans aren’t responsible for the increase in carbon” or even sillier, “CO2 isn’t a pollutant, it’s life!” Every once in a while, however, there arises an argument that isn’t quite so absurd on its face which may require a bit of doing to debunk.

For years, Henrik Svensmark has championed the idea that the current warming can largely be attributed to the variance of cosmic rays and subsequent reduction of cloud nuclei- a hypothesis that has been slightly inconvenienced by the lack of supporting evidence. You can read a succinct and rather amusing take down in Gavin Schmidt’s review of  Svensmark’s book for Physics World.

Back in April, a study published in ERL by Sloan and Wolfendale put the matter to rest for the few rational proponents of the theory that remained. However most lunatic denialists like Senator Jim “[global warming is the] greatest hoax ever perpetrated on the American people” Inhofe aren’t rational people, and the good Senator has propped this little mole back up once more (“cosmic rays” appears at least 25 times in his latest round of FUD).

Unfortunately for Inhofe, his timing couldn’t be worse, as a further debunking of the idea has recently been published in Atmospheric Chemistry and Physics. The study, led by Jon Egill Kristjánsson, went further than Sloan and Wolfendale’s paper from earlier this year and examined MODIS data since 2000 allowing the team to examine cloud factors in addition to cover such as droplet size, depth, and water content. The study concludes:

The overall conclusion, built on a series of independent statistical tests, is that no clear cosmic ray signal associated with Forbush decrease events is found in highly susceptible marine low clouds over the southern hemisphere oceans. Whether such a signal exists at all can not be ruled out on the basis of the present study, due to the small number of cases and because the strongest Forbush decrease events indicate slightly higher correlations than the average events… For the ongoing global warming, however, the role of galactic cosmic rays would be expected to be negligible, considering the fact that the cosmic ray flux has not changed over the last few decades…

Of course, a lack of observable evidence has yet to prove a limiting factor for denialists’ claims. For the rest of us, though, this is yet another nail in the coffin of the cosmic ray argument.

[LATE, LATE UPDATE: New study again refutes the alleged causation.]

Image courtesy of Flickr user “Eyes Closed” used under Creative Commons