The world has been warming faster than expected. Scientists now think they know why

Last year was the hottest year on record, oceans boiled and glaciers melted at alarming rates, and it has left scientists scrambling to understand exactly why.

​ Last year was the hottest year on record, oceans boiled and glaciers melted at alarming rates, and it has left scientists scrambling to understand exactly why. Read More Breaking News, Latest News and Videos | CNN