(2002) We construct a Galactic cosmic ray (CR) diffusion model while considering that CR sources reside predominantly in the Galactic spiral arms. We find that the CR flux (CRF) reaching the
solar system should periodically increase each crossing of a Galactic spiral arm. We search for this signal in the CR exposure age record of Iron meteorites and confirm this prediction. We then check the hypothesis that climate, and in particular the temperature, is affected by the CRF to the extent that glaciations can be induced or completely hindered by possible climatic variations.