Experts seem divided on whether or not Russia's invasion of Ukraine already qualifies as a global war. There's no doubt that the conflict is having negative consequences on an international scale. There are those who claim that these consequences are grave enough to eventually end society as we have come to know it.
I think anyone can envision a scenario whereby V. Putin makes a decision that provokes other powers into direct armed conflict.
The major problem is that there is an individual in power in Russia who can neither admit mistakes nor accept defeat. If this individual cannot somehow be removed from power, peacefully or otherwise, then the future is dark. The destruction of the Ukrainian dam is but prelude. It is almost certain the Ukrainian power reactor is wired for detonation as well. The tactical nuclear missiles in Belarus are not just there for bluster or show. They are undoubtedly targeted on scores of major Ukrainian population centers. Keep your fingers crossed...