It's probably too late for population reductions to save us. If we want to stay below two degrees of warming, massive change needs to happen over the next fifteen years. Not having children, or delaying children can only help a little with this. You won't see a 90% reduction of the population in that timeframe, even if nobody had kids. Keeping population levels approximately constant or falling is important in the long term, but the climate catastrophe is by now a short term problem.

The only realistic way is a huge investment in renewable energy and storage, paired with a steep price on carbon emissions.

I am very far left and I definitely deny the solution of "don't have kids". A below-replacement birth rate would destroy civilized societies. We need to figure out how to reduce emissions per person, rather than just reducing the number of persons. Otherwise we end up in a world with a declining birth rate but a still-increasing median standard of living that continues to destroy the environment

Number one and two has a dilemma. Those who inherits the future will be descended from those that deny that "solution". Earth is going to "die" anyway then.

But pricing carbon and other pollution externalities in is well and good solution, and hopefully will be achievable soon.

I hope it will be achievable soon. See my other comment in this thread (https://news.ycombinator.com/item?id=20121618) to read about the carbon pricing bill that's in US Congress right now.