Earth’s atmosphere protects the biosphere from nearby supernovae

Geological evidence suggests supernovae within 100 parsecs of Earth occur about once per million years. These events can cause intense gamma-ray bursts and significantly increase cosmic rays. This study uses Earth system models to assess the atmospheric effects. Gamma-ray bursts are found to be strongly attenuated. While cosmic rays affect stratospheric ozone, compensating chemical cycles limit depletion. The increase in aerosols and clouds from increased cosmic rays creates radiative forcing comparable to, but opposite in sign to, current anthropogenic forcing. The Earth's atmosphere effectively shields the biosphere from nearby supernovae.

Theodoros Christoudias, Jasper Kirkby, Dominik Stolzenburg, Andrea Pozzer, Eva Sommer, Guy P. Brasseur, Jos Lelieveld