Lab grown meat.
I'm of the opinion that animal agriculture by non-sustainable methods is a major contributor to climate change (maybe even the main contributor, if you believe these guys [1]), but switching any significant segment of the population to plant based diets is politically a non-starter. It isn't talked about and isn't going to happen. A well funded Manhattan project to make lab grown meat palatable and economically viable would be the best shot in the short term at bringing us back from the brink.
What's stopping me is a lack of capital, a lack of relevant expertise, and a lack of the kind of personality that's useful for convincing anyone of anything.
There would be no more problem.
Unlimited time and money? Sure, I would put just about everything that looks human made under ground. The planet would appear mostly uninhabited. The load on the electric grid would mostly vanish as underground temperature is mostly constant near 50F/9.9C and there would be more room for low profile non reflective hidden solar panels. Heating from 50F to whatever people want would be trivial with solar inductive heating, heat batteries, geothermal. Global warming and cooling could be mostly ignored. All the roads would be dozens of layers up and down based on their usage requirements, maintenance loops, locality, interstate, etc... The whole planet would be walkable, e-bikable, scooterable. Internet latency would drop everywhere. Dedicated high speed tubes would get people from anywhere to anywhere in no time.
Whats stopping me? Enough money to bribe everyone into going along with the plan.