As a scientist I’ve learned never to say “never.” So human-caused global warming is always a hypothesis to hold, at least until climate science becomes mature. 

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