The update added to the article is important
Update: Before everyone gets the dickens scared out of them, I'd like to point out that the Crab Nebula is the result of a supernova whose light arrived here in 1054 AD. It's about 6300 light years away.
To the best of my knowledge, absolutely nothing serious happened to the climate in 1054. Apparently, either Buck is right about the pinpoint beam thing, or somebody needs to take a closer look at the numbers or assumptions.