The surface of the Earth was bathed in life-damaging radiation from nearby supernovae on several different occasions over the past nine million years. That is the claim of an international team of astronomers, which has created a computer model that suggests that high-energy particles from the supernovae created ionizing radiation in Earth’s atmosphere that reached ground level. This influx of radiation, the astronomers say, potentially changed the course of the Earth’s climate and the evolution of life.
More details HERE. The part that interested me was the impact of cosmic rays on the climate, through increased cloud cover.
The cosmic rays may have also changed Earth’s climate. The most recent batch of supernovae came just before Earth entered a series of ice ages, at the end of which paved the way for humans to emerge. One possible link between the supernovae and climate is that muons in the lower atmosphere affected cloud cover, thereby cooling the planet.
“When ionization takes place down in the troposphere, where all our weather occurs, what will that do to our weather and climate?” asks Melott. “I’m not going to claim it causes ice ages, but it’s a possibility that needs to be investigated.”
The next step, says Melott, is to scour the geological record, searching for any evidence that supernovae really did have an effect, while further refining the models describing the propagation of cosmic rays from supernovae through space.
A quiet sun reduces the influence of the magnetosphere on cosmic rays, thus more high energy cosmic rays reach the lower atmosphere producing more cloud cover and a cooler planet. Low sunspots could enhance the impact of a supernova.