

If you live in an open and transparent society: there will be an investigation and there is a high chance they will find out. You’ll be expected to take care of the mess with disaster relief for the survivors. Also about 40% of the people did vote for you. Also even the ones who did not vote for you still pays tax.
If you live in a dictatorship: police brutality is cheaper and is a bit more selective in it’s targeting.
Speed up by far. All the focus will be on producing enough stuff to replace whatever the enemy blows up. Any invention in the renewable department will only come as a result of having used all available fuel already.
The world population still increased during the previous world wars so unless we have a major nuclear exchange that probably won’t change. If we do have a major nuclear war global warming is suddenly not a big deal anyway.