This doomsday thinking is just an excuse to pursue an insane goal to try to colonize a planet that has nothing to do with us. As other people here have pointed out, no matter how bad Earth is screwed, it will still be a better place than Mars. If the problem is survival of our species, we should build self sustained bases on Earth (maybe underground) and good planetary defenses against asteroids. The real reason for this insane plan to colonize Mars is not our survival, it is because these people are still in the space age of the 20th century and they think a colony on Mars is very cool. And even if we decide to do it just for fun, it is reasonable to point to note that we are on the verge of an AI revolution, when machines will surpass humans in most of our abilities. Machines are perfect for the space and the hostile environments of other planets, so in 20 years will make no sense to send humans to work on colonization. It makes much more sense to send the machines, wait for them to build farms, factories, mining facilities and cities there, and then just go and chill.