Cosmic Rays, Clouds, and Climate

TLDR

Variations in galactic cosmic ray intensity have been linked to changes in Earth’s cloud cover over a solar cycle, though the reliability of this correlation remains debated. The study aims to investigate the physical mechanisms by which cosmic rays could influence cloud formation to determine whether the observed correlation reflects a causal relationship. The analysis suggests that a cosmic ray–cloud interaction could amplify small solar output variations into larger climate changes, offering a potential explanation for the observed climate sensitivity.

Abstract

It has been proposed that Earth's climate could be affected by changes in cloudiness caused by variations in the intensity of galactic cosmic rays in the atmosphere. This proposal stems from an observed correlation between cosmic ray intensity and Earth's average cloud cover over the course of one solar cycle. Some scientists question the reliability of the observations, whereas others, who accept them as reliable, suggest that the correlation may be caused by other physical phenomena with decadal periods or by a response to volcanic activity or El Niño. Nevertheless, the observation has raised the intriguing possibility that a cosmic ray-cloud interaction may help explain how a relatively small change in solar output can produce much larger changes in Earth's climate. Physical mechanisms have been proposed to explain how cosmic rays could affect clouds, but they need to be investigated further if the observation is to become more than just another correlation among geophysical variables.