Question: What circumstances (theoretical or based on actual past events) could lower the global temperature on Earth or an Earth-like planet to an average of 30℉–40℉ (-1℃–4℃)?


  • Both natrual and man-made solutions are acceptable.
  • The cooling transition may take up to 2,000 years.
  • The "ice age" or final cooled condition would last 500–700 years.

The best answer:

  • Uses the least amount of magic.
  • Causes the least amount of damage to current life on Earth.

I understand that some extinction or endangerment is inevitable.


2 Answers 2


A period of solar inactivity. There are less sun spots and solar flares and the output of the sun drops enough to cause a cooling effect on the Earth.

It's believed to be the cause of the ice ages throughout history.

Solar Inactivity

Diminishing solar activity may bring new Ice Age by 2030


Nazi Necromancers summon an Avatar of Ymir

The allies are closing in and Hitler pulls out all the stops, looking for victory in the occult. Whether or not this thing is actually Ymir, a personification of the collective will of the Aryan people, an esoteric thought form or just an opportunistic demonic being - they pull something through.

And of course, he is about as disinterested in the Nazi cause as you can imagine. He starts the never-ending Fimbulwinter and begins spawning a race of frost giants to inherit the earth.

  • 1
    $\begingroup$ Reviewers! This is in the low-quality queue. Please understand that this was posted in response to the OP's original question. It was a perfectly reasonable (and fairly creative, it'd make a good B-movie) answer back then. Please bear this in mind as you complete your reviews. Past answerers are not notified of question edits. $\endgroup$
    – JBH
    Jul 11, 2018 at 20:28

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