Americans have endured extreme weather this winter, but not just extreme cold.

The ancient Earth has seen its global climate come and go — a few million years of ice-covered cold at times, and long epochs of dry, ice-free warmth at others, all due to the vagaries of nature.

Antarctic Ice Shelf Melt: Remember the Holocene

Foreshadowing potential climate chaos to come, early global warming caused unexpectedly severe and erratic temperature swings as rising levels of greenhouse gases helped transform Earth, a team led by researchers at UC Davis said Thursday.