NOTE: All relative terms (e.g., recent decades, recent global warming) are relative to the respective times of publication of each of these articles.
As with all my lists of this type, most of the papers on it agree with the climate realist perspective on climate change, as defined on the About page. (In this case I think that would mean accepting a large solar forcing on climate and multiple solar amplification mechanisms.) This is because the purpose of all these lists is to show that the climate realist perspective is supported by a substantial portion of the scientific literature.
A controversial hypothesis, originally proposed in 1959 but which only became very well-known in 1997, is a possible link between cosmic rays, clouds, and the earth’s climate. The IPCC and others do not think the “Svensmark hypothesis” (named after the man who popularized it) of ion-induced nucleation holds much merit. I and some papers I shall list respectfully disagree, as with the solar list. To be fair to the IPCC and the other skeptics, though, I must add that there are papers supporting a negligible or absent connection between cosmic rays and climate. In my opinion, there is a solid argument to be made for some kind of connection between cosmic rays and climate, however small it may be. Whether or not they caused recent warming I do not have a strong opinion on yet, though.
Thus, I present a list of significant, select papers on some aspect of the cosmic rays-cloud-climate connection that were published since 1989. Note that I have chosen not to list a good amount of papers because they were written before 1989 or aren’t significant enough to include. Also note that I do not necessarily endorse the findings of these papers, nor do I endorse the opinions of the scientists who wrote them.
However, before listing these papers I believe it is important to have background knowledge. Cosmic rays, high-energy particles composed mainly of solar energetic particles (SEPs) and galactic cosmic rays (GCRs) (the difference being their origin: SEPs come from the Sun and GCRs from supernovae), are modulated by solar activity (more specifically the solar wind), as well as earth’s magnetic field, so higher solar or geomagnetic activity means less cosmic rays strike the earth. (Because of this, a correlation between earth’s magnetic field and climate could be interpreted as evidence of a connection between cosmic rays and climate.) When cosmic rays strike the atmosphere, they produce ions, which could, through multiple proposed mechanisms, form and/or alter clouds. The most well-known mechanism for a cosmic ray effect on clouds is ion-induced nucleation, by which cosmic rays produce aerosol particles in the atmosphere. These particles reflect more sunlight (though not very well at small sizes), make clouds brighter and live longer, and if they grow enough can serve as seeds for cloud droplets to form on. All of those effects cool the earth, so if cosmic rays affect aerosol particles in any way (which they do), they could alter climate. Secondly, cosmic rays could affect clouds by altering the global electrical circuit, which would then alter the electrical properties of clouds around the globe and change droplet collision rates. This affects formation of clouds, which of course would affect the climate. Since the Sun occasionally, for short periods of time, emits large amounts of electromagnetic radiation and plasma which lower the amount of cosmic rays striking the earth, (known as Forbush Decreases), the possibility of such a connection can be studied by measuring if cloud properties change within afterward. In addition, there are other possible effects of cosmic rays on climate and other mechanisms for such an effect, and though they may be included in the list I will not go over them here because their numbers are small.
It’s important to note that because of what’s discussed above, an effect of cosmic rays on climate is a good candidate for a solar amplification mechanism, as discussed on the solar list.
As with all my working lists, it may be incomplete and reasonable new suggestions are welcome. In addition, if anyone has a publicly accessible link to the full paper for those that are paywalled, feel free to show me it.
Just to be fair, I would like to thank PopularTechnology.net for his list of papers on cosmic rays and climate, some of which are also on my list.
GCR – Galactic Cosmic Ray
Why I think it’s important – It argues that evidence has accumulated for an effect of GCRs on climate, that GCRs, including Forbush Decreases, may influence vertical temperature profiles, atmospheric vorticity, cyclones, and jet streams. This paper introduces one of the two main hypotheses for a cosmic ray effect on climate.
Why I think it’s important – It argues that GCRs, by modulation of atmospheric electricity properties, can affect atmospheric circulation, vorticity, and cyclones through influence on cloud microphysics.
Why I think it’s important – It argues that cosmic rays can cause ozone depletion, which would cool the earth (see above).
Why I think it’s important – It argues that GCRs may influence the transparency of the atmosphere, which depends on the amount of aerosol particles in the atmosphere (see above for significance of this). Thus, GCRs may influence clouds through modification of aerosol particle content.
Why I think it’s important – It defends the hypothesis of a cosmic-ray influence on climate via the global electric circuit, and argues that GCRs can influence precipitation, latent heat release, cloud vertical motions, atmospheric vorticity, and general circulation.
Why I think it’s important – It argues, similar to Pudovkin and Babushkina 1992, that cosmic rays can affect atmospheric transparency.
Why I think it’s important – It affirms and reiterates the conclusions of Tinsley and Heelis 1993, and argues that the process described the above paper can provide explanation for correlations observed between the solar wind, atmospheric electricity, and climate.
Why I think it’s important – It argues that Forbush Decreases can affect rainfall. This result conceivably could support a link between cosmic rays and clouds, for less clouds would produce less rainfall.
Why I think it’s important – It argues that Forbush Decreases can influence total cloud cover. This result obviously could support a link between cosmic rays and cloud cover.
Why I think it’s important – It corroborates the findings of Shumilov et a. 1992, and argues that cosmic rays can even form ozone “miniholes”.
Why I think it’s important – It argues that both types of cosmic rays can influence atmospheric circulation and transparency and cloud cover.
Why I think it’s important – It argues that cosmic rays can influence temperature through modification of cloud cover.
Why I think it’s important – It argues that stratospheric aerosol concentration is increased after an increase of cosmic rays, and that this is due to a cosmic ray influence on aerosol concentration.
Why I think it’s important – It argues that the air-Earth current density (associated with atmospheric electricity, ions, and thus cosmic rays) can influence atmospheric dynamics, including cloud properties, precipitation, latent heat release, and storm intensity.
Why I think it’s important – It argues that galactic cosmic rays, by modulating ionosphere-Earth electric currents and thus cloud microphysics, can influence zonal winds, atmospheric circulation, and possibly even important climate features like the MJO and NAO.