What do supernovas and fluffy white clouds have in common? That’s not a riddle, it’s a question several groups of scientists are seeking to answer. A dying star releases vast amounts of energy, some of it in the form of cosmic rays. We know these high-energy particles occasionally slam into Earth’s atmosphere, but what effect do they have? A Danish team suggests that cosmic rays can affect cloud cover, and thus, Earth’s climate.
Most cosmic rays are atomic nuclei that have been stripped of their electrons. These particles (usually hydrogen or helium) travel at a significant fraction of the speed of light. When impacting Earth’s atmosphere, they produce a shower of secondary particles that we can detect on the ground. The new study from Henrik Svensmark at the Danish National Space Institute points to a way this process could produce clouds. Svensmark claims this can even account for significant temperature swings over Earth’s history.
Svensmark and his team based the assertion on experiments with an 8-square-meter cloud chamber. By increasing the number of electrically charged particles passing through the chamber, they were able to coax small clouds to form. This is similar to the ionization effect when cosmic rays strike the atmosphere — it may produce an aerosol that leads to the formation of a cloud.
The study goes on to speculate on the potential scale of this effect with a computer model. Svensmark suggests that clouds generated by distant cosmic events could shift the global temperature by several degrees. More cosmic rays mean more clouds and lower temperatures, and vice versa. Events like the Little Ice Age between 1300 and 1900 CE could allegedly have been caused by our solar system’s passage through waves of cosmic rays.
It’s a pretty wild hypothesis, and Svensmark seems too fast to call this case closed. The scientific community remains unconvinced of “cosmoclimatology” as described in Svensmark’s latest publication. Other researchers question how the small increases in cloud formation demonstrated by Svensmark could have global effects that outweigh cloud-seeding particles already in the atmosphere. Additionally, temperature increases have tracked closely with atmospheric changes, but there’s no such correlation with supernova activity.
This is an interesting idea that will no doubt be studied in detail. CERN has a similar project running to study the effects of cosmic rays on the atmosphere. Thus far, that team has found no reason to expect cosmic rays to have a significant impact on climate or cloud cover. We need much more data than can be gathered in a tiny cloud chamber to say supernovas affect the climate, but it makes for a good headline.
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