In the terms of national security aggression has to be deterred, and nuclear risks managed by the architecture of international order to tackle the self-imposed existential risk to humanity, that of massive technological devastation to the whole planet by the unleashing of nuclear firepower. But now, another series of self-imposed existential risks are looming, caused as a consequence of the success of other forms of firepower, the successful manipulation of combustion to power modern societies. Climate change is now a matter of security too, and international relations thinking needs an overhaul to deal with this new category of threat.