He gave a very clear way out: massively reduce consumption.
Locking people up who turn their heating up too high? Fines for those who eat too many cakes?
I'm being serious -- I can't imagine how such a thing could be enforced, and you certainly can't count on a significant majority of the world reducing their consumption just because it would be good for future generations.
Massively reducing consumption means, for instance: * Eating less meat * Frequent flyers massively reducing long haul flights across the world * Getting rid of energy inefficient appliances, such as old refrigerators
Seriously, the pareto principle applies here to, most of the emissions come from a small percentage of people.
If you think about these things from a carbon budget perspective: Whenever you take a flight you effectively rob the poorest of the world of the possibility to use fossil fuels as a way to increase their welfare.
A 2 degrees increase will kill a lot of people. And this will only get worse with a 4 degrees increase. And it will disproportionally effect the poorest of the world. An average warming of 4 degrees means massive warming of the land surface across the globe (Much more than 4 degrees, since most of the earth's surface is covered by water).
The heat wave of 2003 killed tens of thousands in developed Europe. Imagine the heat waves we will get in a 4 degrees world. Our infrastructure is not built for this. Our asphalt roads, train tracks, water pipes, emergency services will all struggle with this. A city like London has maybe food for 3 days.
Should be done for fossil fuel.
The earth will warm more than 2°C from "baseline" no matter what. Now the 1 trillion ton additional CO2 is an interesting benchmark, but I would guess staying under it has very little to do with energy consumption, and almost everything to do with advances in carbon-neutral and carbon-negative power generation technologies to be invented and scaled over the next century.
But not generating the power in the first place just isn't a choice. If it's a hard-line ultimatum I think a billion people could die trying to fight/enforce it.
The takeaway from OP is that climate changes. It changes quite dramatically. And it changes with or without humans in the mix. Maybe we need to spend that $100 trillion getting more adaptable to changing climate rather than entertaining some fantasy that we can control Mother Nature within some sliver of a temperature range relative to her broad historical performance.