It's cold outside, but that doesn't mean climate change isn't real

Sammy Roth, USA TODAY Published 5:13 p.m. ET Dec. 28, 2017

This week's cold snap has brought record-low temperatures, freezing rain and heavy snow to much of the United States. But 2017 is still on track to be the second- or third-hottest year ever recorded globally — and scientists say climate change is to blame.

Even this week's cold weather is probably being caused at least in part by global warming, said Jonathan Overpeck, a climate scientist at the University of Michigan.

The Arctic is warming much faster than most of the planet, leading to a dramatic decline in the amount of sea ice that covers the region each winter. That loss of ice has allowed more heat to transfer from the ocean to the atmosphere, causing a weakening of the polar vortex winds over the Arctic. Those winds usually "insulate the rest of the Northern Hemisphere" from freezing Arctic temperatures, Overpeck said. But as the winds have weakened, it's gotten easier for freezing Arctic air to swoop further south, he said.