Cosmic rays and climate of the Earth: Possible connection

Despite much evidence relating climatic changes on Earth to solar variability, a physical mechanism responsible for this is still poorly known. A possible link connecting solar activity and climate variations is related to cosmic rays and the physical-chemical changes they produce in the atmosphere. Here we review experimental evidence and theoretical grounds for this relation. The cosmic ray-climate link seems to be a plausible climate driver which effectively operates on different time scales, but its exact mechanism and relative importance still remain open questions.