VARIATION OF COSMIC-RAY FLUX AND GLOBAL CLOUD COVERAGE - A MISSING LINK IN SOLAR-CLIMATE RELATIONSHIPS

In the search for a physical mechanism that could account for reported correlations between solar activity parameters and climate, we have i nvestigated the global cloud cover observed by satellites. We find tha t the observed variation of 3-4% of the global cloud cover during the recent solar cycle is strongly correlated with the cosmic ray flux. Th is, in turn; is inversely correlated with the solar activity. The effe ct is larger at higher latitudes in agreement with the shielding effec t of the Earth's magnetic field on high-energy charged particles. The observed systematic variation in cloud cover will have a significant e ffect on the incoming solar radiation and may, therefore, provide a po ssible explanation of the tropospheric and stratospheric 10-12 year os cillations which have been reported. The above relation between cosmic ray flux and cloud cover should also be of importance in an explanati on of the correlation between solar cycle length and global temperatur e, that has been found. (C) 1997 Elsevier Science Ltd.