Comment: A significant sudden cooling period

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A significant sudden cooling period

would be a drastic enough "regulatory action" on human activity that
tree huggers will be the least of your worries.

FWIW the biggest cooling
events of the last 10,000 years occurred during a period when the general
trend was of rapid global warming. Some of the effects of the third one of
these, which started suddenly at about 8,200 years BP:

Drier conditions were notable in North Africa, while East Africa suffered five centuries of general drought. In West Asia and especially Mesopotamia, the 8.2ky event was a three-hundred year aridification and cooling episode, which provided the natural force for Mesopotamian irrigation agriculture and surplus production that were essential for the earliest class-formation and urban life.