[svara]

But there are some actions that can deliver huge gains immediately (e.g., replacing coal plants by almost anything else) for a low cost (both in terms of money and reduced standard of living / reduced growth). Reducing air travel is great, but there are few alternatives and not doing it at all anymore would drastically change modern society.

A carbon tax would make that discussion moot though: It can be adjusted dynamically to follow a defined CO2 reduction schedule, and carbon savings would come from low hanging fruit first, and ultimately affect everything.

[peterwwillis]

You have to weigh multiple costs, though. What's the cost of waiting to find out if the one huge gain is enough, versus the cost of doing them all right now?

It seems like a lot of the small changes with small impacts could actually cause a larger ripple effect which might end up causing the larger changes. Perhaps small changes, once accumulated, could be the key?