Some results relevant to the discussion of a possible link between cosmic rays and the Earth's climate

Based on a 16-year observation period (1980-1995), it was claimed recently that Earth's climate was linked to variations in the flux of cosmic rays pe netrating into the atmosphere via their postulated effect on global cloud c over. Data from three independent studies yield information relevant to the ongoing discussion of the likelihood of the existence of such a link. (1) Model calculations show that the relative change in the ion production rate from a solar maximum to a solar minimum is of the same order as, or even g reater than,the corresponding change in global cloud cover. (2) However, th e smoothed combined flux of Be-10 and Cl-36 at Summit, Greenland, from 20-6 0 kyr B.P. (proportional to the geomagnetically modulated cosmic ray flux) is unrelated to the corresponding delta O-18 and CH4 data (interpreted as s upraregional climate proxies). (3) Furthermore, although a comparison of th e incoming neutron flux with cloud cover in Switzerland over the last 5 dec ades shows a significant correlation at times during the 1980s and 1990s, t his does not occur during the rest of the period.