A new University of Colorado study suggests that supernovae in the past may have triggered climate change events here on Earth. According to the model, a sudden influx of high energy photons from a supernova could thin the ozone layer, which shields the Earth from the Sun’s rays. Simultaneously, the radiation could degrade methane in the stratosphere, a major contributor to the greenhouse effect that keeps the Earth warm. Put together, these interactions would dampen greenhouse warming and increase the amount of ultraviolet radiation that reaches Earth from the Sun. The study suggests that knock-on effects could include selective animal extinctions, increased wildfires, and global cooling.