Instead of the UN or various militaries, we should be putting trillions into collaborative science efforts like Sustainable Earth or Space stuff.
50 years ago the US (NASA) got to the moon with only a $45b (adjusted) budget, today it is around $20b. If NASA or a sustainable Earth association got to $45b or even 80-100, significant things could happen.
A reduction of the military budget from $693b to $613b would be impactful but quite small. And it would save the environment with the budget cuts to the significantly oil using military vehicles.