We will only see the comet lovejoy every 622 years, that doesn't suggest it's a problem at all, let alone a big one. The fact that the water levels are very low suggest there's a big problem, that we haven't seen them this low in 400 years suggests only that we've seen them this low before and that the world has survived that.
The planet isn't going to die if we irradiate ourselves into caves, but that doesn't mean irradiating the surface of the planet for shits and giggles is a good idea.