Cosmic rays are immensely high-energy radiation, mainly originating outside the solar system. They may produce showers of secondary particles that penetrate and impact the Earth's atmosphere and sometimes even reach the surface. How do they trigger the atmospheric mechanisms?
Some of us think that there is not so much an effect of cosmic rays on the formation of clouds but rather on the growth and possible maintenance of clouds. Cloud droplet growth near cloud edges is a very subtle process, and can be modulated by the electric properties of the atmospheric column, which are in turn strongly modulated by cosmic rays. There are several observational papers (including some of mine) with plausible mechanisms published.
The short answer is that they don't.
There was a hypothesis that cosmic rays generate a cascade of particles in the atmosphere which act like condensation nuclei. However, there is so much dirt in the atmosphere that there is never really a shortage of condensation nuclei. Instead the hypothesis was reached on the basis of correlations between clouds and cosmic ray intensities. So the hypothesis has not been properly tested. Or rather, some work in the lab, as part of the German solar research programme which was designed to test the hypothesis that sub-atomic particles can influence cloud amounts was shown to be inconclusive, if I recall correctly.
The problem with correlations between atmospheric quantities and cosmic rays is that this is equally equivalent to an anti-correlation between atmospheric quantities and the solar cycle. The point being that cosmic rays and the solar cycle are themselves anti-correlated. This is a definite piece of science since the mechanism is that the solar wind actually displaces cosmic rays, so during periods of high solar activity fewer cosmic ray particles penetrate into the atmosphere. so, in the end, what appeared to be a correlation between cloud amounts and cosmic rays might actually be a relationship between the solar cycle and cloud amounts.
The effects of the solar cycle on the atmosphere are very subtle and quite complex. There is of course the total solar irradiance effect which varies a little and this would cause a slight oscillation in global temperature, but just a few tenths K. Then there is the UV effect which changes stratospheric ozone and may lead to an enhanced signal. All of these effects can be coded into a climate model, which can be run for a hundred years or more, but ultimately, the results obtained would likely be model-dependent. It's a case of more research is needed!
John Austin.
John(/George)
Experiments: an addition/correction: it was not "some work in the lab" but at world-famous CERN, the CLOUD-program specifically designated to test Svensmark's ideas on this.
The IPCC Ar5 report is quite conclusive on the insignificance of the process, along the lines you indicate, also because the amount of material needed so that particles can serve as cloud nuclei is not formed from the cosmic radiation
http://www.climatechange2013.org/images/report/WG1AR5_Chapter07_FINAL.pdf
7.4.6 Impact of Cosmic Rays on Aerosols and Clouds
Harry,
Sorry to sound flippant. I was responding without specific notes, and was really thinking of a study supported by the German CAWSES programme, which I've now checked and find that those measurements were made in Karlsruhe. The study I was thinking of was D. Rzesanska et al., "Laboratory Experiments on the Microphysics of Electrified Cloud Droplets", Climate and Weather of the Sun-Earth system (CAWSES), F-J. Luebken (Ed.), 89-107, Springer 2013. I've not been involved with IPCC for a few years, but my ignorance of the latest work on this topic is no excuse, I admit.
As a modeller, though, I would equally have said "some climate model or other" referring without notes to the equally world famous Hadley Centre (UK) or GFDL (US) climate models!
John.
John
My mentioning of CERN was also with tongue in cheek: the experiments were actually rather redundant, because of the knowledge that there is insufficient material to grow the particles to CCN size. However Svensmark's hype made it possible to carry out the expensive tests in a cloud chamber with money imo better spent on science
In our simple laboratory, I succeed to fine impact of the ionization on cloud formation. but the accurate impact of cosmic ray is unknown for me.
Hello,
Very simple subject in theory, very complex in theory.
https://www.researchgate.net/publication/263620997_Possible_effects_of_atmospheric_teleconnections_and_solar_variability_on_tropospheric_and_stratospheric_temperatures_in_the_Northern_Hemisphere?ev=prf_pub
https://www.researchgate.net/publication/259903781_Clouds_blown_by_the_solar_wind
Article Possible effects of atmospheric teleconnections and solar va...
Article Clouds blown by the solar wind
Some of us think that there is not so much an effect of cosmic rays on the formation of clouds but rather on the growth and possible maintenance of clouds. Cloud droplet growth near cloud edges is a very subtle process, and can be modulated by the electric properties of the atmospheric column, which are in turn strongly modulated by cosmic rays. There are several observational papers (including some of mine) with plausible mechanisms published.
Maarten
You refer to this?
https://www.researchgate.net/publication/41571246_Enhancement_of_cloud_formation_by_droplet_charging?ev=prf_pub
Article Enhancement of cloud formation by droplet charging
Yes, amongst other papers that I co-authored, but I did not want to advertise my own papers; there are several research groups interested in t
https://www.researchgate.net/profile/Dimis_Poulos
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