If you were in charge tomorrow, what concrete, measurable milestone would you have the most the talented scientists and 0.4% of GDP go to solving?

Energy breakthroughs (likely fusion or geothermal)

Excessive available energy can solve a lot of problems.

I'm online sometimes

https://bento.me/m-j-r

Yea, desalination and carbon capture are two projects that could change a lot if we had lots of excessive energy to power them.

energy breakthrough + water purification + cross-continental network of pumped storage would probably eradicate famine, arid environments, and climate control for starters.