A new study just published in the Aug. 19th issue of Journal of Geophysical Research: Space Physics comes down in favor of cosmic rays. A team of scientists from the Technical University of Denmark (DTU) and the Hebrew University of Jerusalem has linked sudden decreases in cosmic rays (called "Forbush Decreases") to changes in Earth's cloud cover.
If true, that's amazing. It would also underscore the importance of measuring cosmic rays in the atmosphere. Recent balloon flights by Spaceweather.com and Earth to Sky Calculus show that cosmic rays are intensifying. Cloudy days, anyone?