https://www.sciencedaily.com/releases/2019/07/190703121407.htm
New evidence suggests that high-energy particles from space known as galactic cosmic rays affect the Earth's climate by increasing cloud cover, causing an 'umbrella effect'.
"The Intergovernmental Panel on Climate Change (IPCC) has discussed the impact of cloud cover on climate in their evaluations, but this phenomenon has never been considered in climate predictions due to the insufficient physical understanding of it," comments Professor Hyodo. "This study provides an opportunity to rethink the impact of clouds on climate. When galactic cosmic rays increase, so do low clouds, and when cosmic rays decrease clouds do as well, so climate warming may be caused by an opposite-umbrella effect. The umbrella effect caused by galactic cosmic rays is important when thinking about current global warming as well as the warm period of the medieval era."