Negative emissions tech: can more trees, carbon capture or biochar solve our CO2 problem?

As CO2 levels rise, controversial techniques including carbon capture and storage, enhanced weathering and reforestation may be solutions

In the 2015 Paris climate agreement, 195 nations committed to limit global warming to two degrees above pre-industrial levels. But some, like Eelco Rohling, professor of ocean and climate change at the Australian National University's research school of earth sciences, now argue that this target cannot be achieved unless ways to remove huge amounts of carbon dioxide from the atmosphere are found, and emissions are slashed.

This is where negative emissions technologies come in. The term covers everything from reforestation projects to seeding the stratosphere with sulphates or fertilising the ocean with iron fillings.