How Much Hotter Are The Oceans? The Answer Begins With A Bucket

If you want to know what climate change will look like, you need to know what Earth's climate looked like in the past — what air temperatures were like, for example, and what ocean currents and sea levels were doing. You need to know what polar ice caps and glaciers were up to and, crucially, how hot the oceans were.

"Most of the Earth is water," explains Peter Huybers, a climate scientist at Harvard University. "If you want to understand what global temperatures have been doing, you better understand, in detail, the rates that different parts of the ocean are warming."

Easier said than done.