Guardian: I have often said that global warming is really ocean warming. As humans add more heat-trapping gases to the atmosphere, it causes the Earth to gain energy. Almost all of that energy ends up in the oceans. So, if you want to know how fast the Earth is warming, you have to measure how fast the oceans are heating up.
Sounds easy enough at first, but when we recognize that the oceans are vast (and deep) we can appreciate the difficulties. How can we get enough measurements, at enough locations, and...