In 1983 there was a movie called "War Games". It introduced the concept of DEFCON, or defense condition. It related to nuclear war. Recall that the only way to win is not to play! One suspects we are reaching DEFCON2, with Putin threatening all out nuclear war the DoD may very well have all forces on full alert. DEFCON1 is all out destruction.
The man must be insane to make such threats, it shows a malignant lack of understanding that there is no win in such a situation. Global warming will be taken care of in a global nuclear cloud. The only things remaining are my ginkgos, descendants from the Hiroshima blast.
The last time we faced this was with Kennedy and Cuba. Biden is no Kennedy and the current team in DC is no WW II survivors. In addition Russia has massive nuclear capacity, not to mention the US.
Hopefully some Russians can see the light and remedy the situation before a total calamity.