Warmer winters can wreak as much havoc as hotter summers, say scientists

Warmer winters are happening across the globe, and can be drivers of catastrophic weather events and profound changes

As climate scientist Kai Kornhuber walks around New York City this winter, an eerie feeling creeps into his body. It's warm enough for a T-shirt in December, and the birds are chirping loudly.

The temperatures tell birds and trees that it's time for action, but the systems are out of sync for December, says Kornhuber, a postdoctoral researcher at Columbia University's Earth Institute.