I am speaking specifically about Betelgeuse. I do not believe it's possible for Betelgeuse to cause 3-4C global temperature increase. Assume Betelgeuse explode

I am speaking specifically about Betelgeuse. I do not believe it's possible for Betelgeuse to cause 3-4C global temperature increase. Assume Betelgeuse explodes in a typical Type II-P supernova. This will give it an absolute magnitude in the ballpark of -16.5, call it an even -17. Betelgeuse is approximately 220 parsecs away, which would give an apparent magnitude of 5*(log10(220) - 1) - 17 = -10.3. The full moon is -12.9, so is approximately 10 times as bright. Specifically regarding energetic particles, the amount of material blown out at relativistic speeds from a II-P supernova is negligible. The high energy interactions happen way inside the star's envelope. The high energy stuff all gets absorbed and re-emitted as lower energy light. The plateau in the light curve of a Type II-P supernova is caused because the outer layers are completely opaque and are trapping energy in the interior. That's actually the reason I keep contrasting Type II-P with gamma ray bursts. In those events, the outer layers have been stripped away, and we have a direct view on the high energy interactions happening in and around the collapsing core. There is no material to block it, so everything about it is more intense; there are vastly more high energy particles spilling out as cosmic rays, the peak brightness is much brighter, and the light that is emitted is much hotter. Basically, supernova are fundamentally different from each other. They're a family of phenomena, not just one thing. A gamma ray burst directed at Earth will be catastrophic at 1000ly; (which is why the article talks about supernova up to 1000ly) a Type II-P supernova at 10ly will be comparably catastrophic, but simply won't register at 700ly.