That's 5x larger than the Krakatoa explosion; huge but not alone big enough to exterminate humanity. The most dangerous nukes are actually the smallest, since

That's 5x larger than the Krakatoa explosion; huge but not alone big enough to exterminate humanity. The most dangerous nukes are actually the smallest, since politicians may convince themselves that just a few small nukes is permissible, resulting in a rapid escalation that sees every major city showered with megaton h-bombs, destroying civilization and sending humanity into a poisoned dark age. If it seems implausible that politicians might use tactical nukes, ask what those nukes were created for. The US made many thousands of them to be used against a conventional Soviet ground invasion of West Germany; lobbing small nukes at tank columns. Escalation from a conventional war to a nuclear war was a common assumption in the military planning of the late cold war. But sides anticipated it and were prepared to perform that escalation themselves.