On relationship between Galactic Cosmic Rays and Cloud cover

Intriguing relationship between Galactic Cosmic Ray (GCR) and Cloud Cover (CC) puts a challenge in understanding climate variability and global warming. Correlation obtained between Galactic Cosmic Ray and Cloud Cover is explained by ionization of air molecules due to cosmic rays. This atmospheric ionization affects cloud nucleation and hence changes distribution of cloudiness. On the other hand, clumping of aerosols resulting from ionization is yet to prove. Uncertainty in cloud measurements is another barrier for proving any specific relationship between Galactic Cosmic Ray and Cloud Cover.