Galactic cosmic ray and El Niño–Southern Oscillation trends in International Satellite Cloud Climatology Project D2 low‐cloud properties

Abstract

The recently reported correlation between clouds and galactic cosmic rays (GCR) implies the existence of a previously unknown process linking solar variability and climate. An analysis of the interannual variability of International Satellite Cloud Climatology Project D2 (ISCCP‐D2) low‐cloud properties over the period July 1983 to August 1994 suggests that low clouds are statistically related to two processes, (1) GCR and (2) El Niño–Southern Oscillation (ENSO), with GCR explaining a greater percentage of the total variance. Areas where satellites have an unobstructed view of low cloud possess a strong correlation with GCR, which suggests that low‐cloud properties observed in these regions are less likely to be contaminated from overlying cloud. The GCR‐low cloud correlation cannot easily be explained by internal climate processes, changes in direct solar forcing, or UV‐ozone interactions. Instead, it is argued that a mechanism involving solar variability via GCR ionization of the atmosphere is consistent with these results. However, the results are marginal when including the recently extended ISCCP‐D2 data covering the period until September 2001. This, we believe, is related to problems experienced with the ISCCP intercalibration between September 1994 and January 1995.

The role of atmospheric ions in aerosol nucleation – a review

“…Dickinson (1975) speculated on how ions can influence aerosol nucleation and clouds; later Arnold (1980) suggested that multi ion complexes can serve as condensation nuclei in the stratosphere, and Turco et al (1998) argued that the recombination of ions could nucleate aerosols. In 1997 the role of ionisation from galactic cosmic rays was linked with cloud formation based on satellite observations of clouds and ground based cosmic ray measurements (Svensmark and Friis-Christensen, 1997;Marsh and Svensmark, 2003). A similar connection was later discovered by Harrison and Stephenson (2006) for the UK.…”

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