Cosmic Rays, Clouds, and Climate

Abstract

It has been proposed that Earth's climate could be affected by changes in cloudiness caused by variations in the intensity of galactic cosmic rays in the atmosphere. This proposal stems from an observed correlation between cosmic ray intensity and Earth's average cloud cover over the course of one solar cycle. Some scientists question the reliability of the observations, whereas others, who accept them as reliable, suggest that the correlation may be caused by other physical phenomena with decadal periods or by a response to volcanic activity or El Niño. Nevertheless, the observation has raised the intriguing possibility that a cosmic ray-cloud interaction may help explain how a relatively small change in solar output can produce much larger changes in Earth's climate. Physical mechanisms have been proposed to explain how cosmic rays could affect clouds, but they need to be investigated further if the observation is to become more than just another correlation among geophysical variables.

Solar wind-atmospheric electricity-cloud microphysics connections to weather and climate

“…While ion-mediated nucleation of condensation nuclei on cosmic-ray produced ions (Dickinson, 1975;Carslaw et al, 2002;Kirkby et al, 2011) has been postulated as a source for CCN and cloud microphysical changes related to Forbush decreases and 11-year cycles of GCRs, it cannot account for the Mansurov, Burns, Veretenenko or Wilcox effects. For these, there is no correlated change in cosmic ray flux and ion production in the lower troposphere, where the responses of cloud cover and vorticity are seen (there can be changes in ionization in the middle atmosphere that modulate J z ).…”

Solar Influence on Global and Regional Climates

“…A long-standing suggestion is that cosmic rays can aid the formation of clouds (see reviews by Ney 1959;Carslaw et al 2002;Kirkby 2007). This would be a highly significant effect because clouds modulate Earth's energy balance by changing the albedo A and by enhancing the infrared greenhouse trapping effect.…”

Possible effect of extreme solar energetic particle events of September–October 1989 on polar stratospheric aerosols: a case study

“…Cosmic rays produce a direct effect on the Earth's atmosphere via ionization of the ambient air and form the main source of the atmospheric ionization for the lower and middle atmosphere (Bazilevskaya et al, 2008). There are some indications that it may affect properties of the atmospheric aerosols (Kazil et al, 2008;Mironova et al, 2008Mironova et al, , 2012 and possibly even cloud formation (Carslaw et al, 2002;Tinsley, 2008), which may be crucially important as an indirect factor affecting the climate. However, it is still a subject of intensive debates (Kulmala et al, 2010;Usoskin et al, 2010b;Calogovic et al, 2010).…”