Now, when we’re exploring these possible futures, we will be proceeding dialectically. Going from one end of the spectrum to the other, and attempting to sift the truth from each shift.
So, for starters lets examine the two polar opposites of possibility: all bad, and all good.
World 1: All best cases. This is essentially the vision of the future put forth by transhumanists and extropians like ray kurzweil, hans moravec, etc. Not because they actively concern themselves with population, climate, and energy, but rather that their vision of technological determinism assumes that all these things go well, without really speaking of it, or they inflate the power of technology to the point where it trumps everything else, which, historically has tended to be true, so it’s a fair assumption to at least argue from.
Technology makes unlimited energy possible, and the associated economic progress causes population growth to subside. If carbon dioxide or methane are an issue, genetically engineered biorgs, or nano-factured carbon sinks offset the problem. Everything eventually becomes so efficient and powerful, we need not burn fossil fuels or toxify the environment any further. The only limitation left for us is our own psychology.
Cue the music from 2001: A Space Odyssey…
World 2: All worst case. This is the brainchild of the most wildly paranoid primitivists and even they don’t really take it seriously.
The world sails off a thermodynamic cliff, but technology manufactures just enough low grade foodstuff to keep an ever increasing population alive at an extremely meager subsistence level, and little else besides. Some sort of cheap engineered seed of an extremely resilient type, or a nanotech device for creating lots of nitrogen phosphate makes this possible. Either that or soylent green.
Quality and expectancy of life plummet. These pressures are compounded by climate collapse, as a diaspora onto the open oceans or inland begins, and hurricanes wreck what’s left of the energy infrastructure. The rolling blackouts apply pretty much everywhere except the pockets of technology that are developing targeted bioweapons, swarming killer drones, and tactical AI’s to fight resource wars.
Eventually the earth turns into an apocalyptic wargame for posthuman intelligences who devastate the earth in attempts to eliminate each other. This lasts until energy constraints bring the thing to a standstill, and the biosphere devolves into a hellworld of killer transgenic monstrosities, wretched starving people and permanent darkness in a frothing ecological super-storm. There’s no way for anyone to get to safety because with the vast throng of people and shrinking landmass, there’s no where left to go. Eventually the cascading combination ( an engineered pandemic amongst a tightly packed global population of 12 billion or so, and no particular medical infrastructure or pharmaceutical industry left, is a likely candidate) wipes us out below replacement level and we go extinct. The AI’s eventually break down and undergo their own entropic collapse, and fail to outlive us by long. Some exceptionally virulent engineered killer takes our place at the top of the food chain, and begins their slow trek towards intelligent folly. The End.