We do not need "depopulation, as I specifically noted in my comment there is no issue with our population numbers being significantly higher than they are, let alone at our current levels. The issue is the kinds of technology that we are using and policies that we have, oil-based transportation, cow-based agriculture and to a lesser extent meat-based agriculture, food waste, coal-based energy generation, etc. We need to decarbonise the grid and transportation (we already know how to do this, it is only a matter of doing it), significantly reduce GHG emissions in agriculture through selecting different crops and livestock as well as increasing efficiency (this will need large scale public buy-in, so it needs to be led by the government), and put serious R&D into decarbonising heavy industry like steel and cement production. Once we get that far, we can focus on solving the remaining GHG issues like synthetic fuel for planes + high-speed rail replacements, and carbon capture & sequestration for what we can't solve in a cheaper way. "Depopulation" is an absurd, unrealistic, and unworkable proposal that does not actually solve the central problem and would actively make it worse. Population size is a huge part of what makes us able to achieve significant scientific and technological progress, "depopulation" would actively harm our efforts to restructure our economy and distribute technology as necessary to combat climate change.