I used to have a blog about Earthship Villages and sustainable survivability through them having a small variety of manufacturing ability and talent, cooperative interior year around gardens and seasonal fields for grains and other food, pastures for some animals, and forest for backup wood stoves and materials. Well defended and use of golf cart type electric vehicles. Enough couples of the right age to prevent genetic erosion, and remote enough to be away from gangs of thieves and cannibals. Enough food storage capability to last through several bad seasons from AGW effects. I realized that not all Earthship Villages would make it as climate worsened, or if they were attacked by a more well armed and larger gang.
With the idea of going past the tipping point for first tundra methane self-release, then oceanic methane hydrates self-release, to the point of worse conditions than the Paleocene-Eocene Thermal Maximum, 10 times as fast, and an Extinction Level Event by 2300 to 2500, the Earthship Village concept doesn't work as well.
I thought of the Bushes and "Rev." Moon's vast acreage over the last untapped large aquifer in extreme northern Paraguay on the Bolivian and Brazil borders. How Bush had an airfield built nearby with 500 special forces type guards. An underground nuclear powered bunker complex with centuries of supplies, grow lights, strict population control, and air filtration. Then I realized that eventually they would have to surface during this period. Equatorial jungle type areas faired better during PETM, so perhaps they could survive with the proper testing equipment for toxins, and living in hot conditions on a diet that is a lot different. A "Brave New World"?
There are additional problems. If the population does not have a die off event mid century and humans continue to burn fossil fuels until they are totally gone, then a runaway greenhouse effect could destroy the biosphere forever. If resource/overpopulation/religion driven warfare goes to large scale nuclear war, that could also sterilize most of the planet. The beginnings of lower strength magnetosphere and pole reversal have started, with the ozone layer still weaker. This is another thing that could be a problem for much of life on Earth. Low strength magnetosphere shield with low strength ozone shield and coronal mass discharge hit. Maybe the biosphere will be lucky.......