We'll all die. It's not so terrifying as depressing. Clathrate gun means death for essentially everyone. Maybe Bezos and Musk are right to make off planet life temporarily viable. Modern society is based on relatively predictable large scale agriculture being able to redistribute goods (transportation infra, tech to support distribution). We simply, as a society, are not capable of adapting to those circumstances. Most humans would die and the survivors would not enjoy a modern lifestyle.

I think humanity can handle (adapt to) the combo of forests burning, ocean acidification, and thawing tundra. At great cost, measured in lives, gold, and lost opportunities, of course.

Until recently I considered the "clathrate gun" to be an extermination event. The earth hasn't had those level of CO2 and methane (in the air) since the Eocene (~2000 CO2 ppm). It's hard to imagine industry and agriculture functioning in that context.

But perhaps humans are more resilient. There's growing evidence validating the Young Dryas theory, where the global temps plunged and then spiked 1000 years later. Somehow humans survived, even though our fledgeling civilization was reset.