It isn't statistically probable that we will encounter a supervolcanic eruption within the next century (or even millennia). But it isn't statistically probable that an asteroid will hit us either, and that doesn't stop us from preparing for the worst.
Uncertainty in exactly how something happens does not translate into uncertainty that it is happening. There is no rational basis for denial of the reality, or the risks, of global warming. And there is no excuse for ignoring it.
Today scientists are closely tracking 434 asteroids that are large enough and come close enough to the Earth to be of potential future concern, and while none of these pose any significant risk today, increased surveillance is required.
The probability of impact by one of these before the end of the century is 0.0005 percent. On the other hand, recent research suggests a 2 percent probability of global catastrophe from anthropogenic climate change by the end of this century.