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SOURCE: Scientific American

DATE: March 13, 2018

SNIP: The Intergovernmental Panel on Climate Change, in its Fifth Assessment Report, presented more than 100 modeled scenarios that it said had a high likelihood of keeping global temperatures within 2 degrees Celsius of preindustrial levels. Nearly all of them assumed that negative emissions technology would be viable and widely used, particularly BECCS.

The idea calls for massive plantations of trees and other crops to draw carbon dioxide out of the air. The trees could then be harvested for the production of energy or biofuels, with carbon capture technology used to sequester their emissions. The whole process would be carbon-negative. This could theoretically cool the climate. But it would have to be done at a massive scale.

It’s still almost an entirely hypothetical concept. But it has rapidly risen to prominence as a strategy for meeting the world’s climate targets established under the Paris Agreement.

But there’s a major problem: Research increasingly suggests that the process is not feasible at the scale necessary to make a real dent in global climate goals—at least, not without causing massive environmental or social disruptions. If that’s the case, some experts worry that the models could mislead policymakers into believing there’s a definite “out” if global emissions don’t fall fast enough in the future.

A study published in the journal Nature Climate Change in January is among the latest to raise doubts. It suggests that the large-scale deployment of BECCS—which calls for massive, managed plantations of trees—would likely require an unsustainable use of land, water and other resources.

“Our main message is that really relying on BECCS via the land system is a very high risk to the Earth system in general,” said the paper’s lead author, Vera Heck of the Potsdam Institute for Climate Impact Research in Germany.