"Scientists know that the Arctic is warming about twice as fast as the rest of the planet on average, a phenomenon known as Arctic amplification," writes Michael Lemonick. "And they have a pretty good idea of why: warmer temperatures lead to more meltback in sea ice in the summer, which exposes more ocean water. The water, which is darker and less reflective than ice, absorbs energy, heats up and warms the air in turn, leading to even more melting. It's a classic feedback loop, and it makes all sorts of sense"