A piece of coal at the Neryungrinsky coal mine of Yakutugol, a part of Mechel Group of Companies | Artyom Geodakyan\TASS via Getty Images
Climate

The Formation of Today’s Planet-Warming Coal Nearly Froze Earth Long Ago

The planet was nearly a snowball during the Carboniferous Period about 300 million years ago, when forests died and slowly transformed into coal.

Published On 10/09/2017
3:49 PM EDT