We're going to need a bigger bucket of water.
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We're going to need a bigger bucket of water.

Global warming could be reversed using a combination of burning trees and crops for energy, and capturing and storing carbon dioxide underground (CCS), according to an analysis by scientists. But experts cautioned that trying such an approach after temperatures had passed dangerous levels could be problematic, as climate change reduced the number of trees available for "bioenergy."

The bioenergy and CCS method was the most cost-effective way of tackling carbon emissions, said the team at Chalmers University of Technology in Sweden, publishing their research in the journal Environmental Research Letters on Thursday. Such an approach could offset and even reverse other emissions from fossil fuels, they claimed.

The lead author of the study, Christian Azar, said it could help bring temperatures down even if they rose above the 2 degrees C level that world leaders have agreed to avoid: "Even if current political gridlock causes global warming in excess of 2 degrees C, we can reverse the temperature trend and reach targets later. This means that 2 degrees C targets, or even more ambitious targets, can remain on the table in international climate negotiations."

He said that to achieve a reversal of temperatures, the combination of bioenergy and CCS would need to be combined with a huge expansion in renewable energy or nuclear power, in order to reduce emissions almost to zero. He also admitted that there was a political risk that the proposal's ability to reverse rises at a late stage could be used as an excuse for short-term inaction on emissions.