Thought experiment:
What about reforestation on a massive (yet manual) scale?
Plus strict population controls.
Plus FDR-scale decarbonization and sustainable agricultural projects - in every country around the globe all at once.
Without using carbon-based energy to power all this projected work.
If you want your ration of Soylent Green (or sustainably produced local food paste), you take the rail or walk to The Project and wield the pick and shovel. Perhaps developing EV based public transport and heavy construction equipment could be prioritized.
Throw in massive, fast-adoption of modern, smaller-scale nuclear power.
And let’s further toss in a dire assumption that 2 billion people die rather quickly.
I know that is pie-in-the-sky and ‘people’ aren’t wired for that. It would require totalitarian + religious levels of control and brainwashing. Would that be able to stave off what is coming, and perhaps get the Lower Emissions Scenario or better?
BTW: I generated about 11 kWh from my 6 panels today (2.1 kWh system, off-grid), and pounded most of that into my EV car. In a few weeks the installers are coming to put a grid-tied 10kWh system on my roof.
Our chance to do this voluntarily and make it our ‘culture’ and the basis of our societies was between 125-150 years ago, with the last gasp about 60 years ago.