Cutting carbon emissions is better than carbon removal, says study

Science : Although carbon dioxide removal (CDR) from the atmosphere has been proposed as one method to mitigate global warming, a new study shows that it would have only limited effect. Sabine Mathesius of the Potsdam Institute for Climate Impact Research in Germany and colleagues used computer simulations to model the effects of removing about half the atmospheric CO₂ currently being emitted from manmade sources. Such an effort would require some 5000 new facilities, each the size of a sports stadium, and could cost a trillion dollars. Yet the researchers found that the environmental benefits were surprisingly small. That’s because CDR removes CO₂ from the air but not from the deep ocean, which has been shown to be a significant carbon sink.The carbon sequestered in seawater, organic matter, and the shells of sea creatures takes thousands of years to return to the surface, so the only way to significantly reduce ocean acidification, they say, is to cut the amount of carbon being emitted into the atmosphere. “Our paper shows that emitting CO₂ today and taking it out sometime later is not the same as never emitting it at all,” says study coauthor Ken Caldeira.