Earth's oceans can absorb a tremendous amount of heat. Covering 71% of the surface, they act as a buffer, absorbing over 90% of the heat produced by global warming. But there's a limit.  

Although they may absorb enough heat to keep the planet from becoming completely uninhabitable, the oceans themselves nurture a complex and delicate web of sea life. Here are five ways that rising temperatures threaten to upset the balance, eliminating important species and threatening the food sources and livelihoods of hundreds of millions of people.