The recent ®nding of a signi®cant correlation between variations of the cosmic ray ¯ux and the global cloud coverage by Svensmark and Friis-Christensen (1997; hereafter abbreviated S&FC) lent countenance to the idea that cosmic rays might aect the Earth's weather and climate, which was suggested 40 years ago by Ney (1959). To establish their correlation, S&FC used normalized cosmic ray ¯ux data from various observatories around the world, one located in Peru, one at Moscow (Russia), and the remaining three in North America. Cloud data were obtained from the International Satellite Cloud Climatology Project (ISCCP, Rossow and Schier, 1991), and additional satellite data sources, viz. from the NIMBUS-7 CMATRIX project, and from the Defense Satellite Meteorological Program (DMSP) Special Sensor Microwave/Imager (SSM/I). The correlation found by S&FC provides an interesting hint of a possible physical mechanism that is able to link solar activity phenomena to atmospheric variability. However, in an attempt to emphasize the importance of their results for global climate variability, the authors interpret this correlation in a very bold way that is Ð in our opinion Ð not justi®ed considering their sparse data base. In the following we shall give some arguments for why we think that S&FC's con-