First, the corrections: The first sentence of the second paragraph needs either an added word (add and before so) or a comma and an added word (add it after so) to make sense. I went with the second option, but either would work. The em-dash in the next sentence needs to be changed to a comma, and 50 needs to be changed to fifty.
Earth is threatened by a new ice age, promising to freeze the planet solid for thousands of years.
Humanity cannot look to the stars for asylum, so it decides instead to move underground. Governments from all over the world come together and pool both money and resources to create underground cities for the time of the ice age’s arrival, which is estimated to be within the next fifty years.
This is, in my opinion, a highly unrealistic scenario (despite making for pretty good fiction if handled properly). Earth is threatened by a new ice age, although it probably won’t be a Snowball Earth situation where the ice sheets join at the equator. But do you see governments from all over the world doing much of anything to prepare for the problem, since, y’know, they’re not doing much of anything to prepare for the problem? Can you honestly imagine most people donating money and other resources to build shelters for someone other than themselves — and only themselves?
Also… ice ages really can come on a lot faster than you may think. Remember that movie The Day After Tomorrow? Remember how nearly everyone said how unrealistic it was because the ice age came on in just a few weeks? There is strong evidence that it can happen even faster than that, though: mammoths have been found frozen upright with food still in their mouths, for example.
(WordPress’ spell check wants me to change pool to pull, making it pull both money and resources. *shakes head* But yeah, keep telling me how computer programs do everything better than any person can…)