Donald Trump could "solve" global warming in less than 30 minutes with a call to the military. Vladimir Putin has a similar option. Depopulation and nuclear winter would do the trick.
Of course I am being glib, but we are living in a world where two people have the power to end civilization any time they want to. Something that I think is important to remember when talking about risks of AI.
For risks of nuclear deterrence one would hope that the military would follow Trump's orders, for humanity one would hope that they would not because he's about as stable as 74 year old nitroclycerine.