The oceans control climate change. Not only do the world's waters absorb the bulk of the extra heat trapped by greenhouse gases in the atmosphere, they also absorb the bulk of the extra carbon dioxide. And that means one thing: a more acid ocean. 

New research shows that while some shell-forming sea critters, like lobsters, will actually build thicker shells in a more acid ocean, clams and oysters, among others, have shells that partially dissolved under the new conditions. And tiny creatures known as foramnifera are already building less thick shells as a result of a drop in ocean pH from 8.2 to 8.1 over the course of the last century. That tenth of a point on the logarithmic pH scale actually means a roughly 30 percent increase in acidity. 

Warmer water also takes up more space. That's led to sea level rise of 17 centimeters over the 20th century, enough to erode or submerge some 60 extra feet of beach on the U.S. East Coast. 

Nothing agreed in Copenhagen or hereafter will be able to stop either this thermal expansion of the seas or the rising acidity of the waters. That would take actually reducing the amount of CO2 in the atmosphere, perhaps through devices to pull it out of the air. 

Already, human impacts on the ocean are large, from spurring jellyfish to dominate to boosting algae blooms and dead zones. The Baltic Sea that Copenhagen guards is the world's largest such dead zone. With water, water everywhere, perhaps it's time to think.

—David Biello

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