Expert: Philip Stahl - 11/2/2009

Question
Is it possible for solar flares or some other solar activity to bombard Earth with increased UV radiation so that enough passes through the atmosphere to do serious damage to people? I don't mean just sunburns, but enough UV radiation to cause widespread, fatal skin cancer, especially in light-skinned individuals? This is unrelated to the crazy 2012 "doomsday" scares. I'm writing a story where European civilization collapses before Columbus sails to the Americas, and I need a scientifically plausible cause for the demise of European society but not other societies.

Answer
Hello,

Unfortunately, there are few genuine scenarios for such an event unless the flare was absolutely humongous - maybe 1 million times more powerful than the August, 1972 flares that eroded more than 20% of the then ozone layer.

Recall it is this layer which protects us from most of the harmful UV radiation. So your hypothetical would require either: a) a monster flare that could  effect nearly 90% or more erosion of the layer - then trigger a series of (similar) homologous flares, or b) some other external agent eroded the ozone layer (nearly all of it) before an energetically intense (say class X-9) flare was triggered.

Both of these are highly improbable, though I am not sure I'd insist they were "impossible".