https://phys.org/news/2018-06-power.html

It turns out that these are the activities that crucially determine how much carbon dioxide will be emitted within this century; if and how much the world will have to rely on negative emissions and ultimately if the internationally agreed climate targets can be met.

The Paris targets of keeping global warming well below 2°C and possibly even at 1.5°C imply a tight limit on cumulative CO2 emissions until 2100. To put this into perspective: the remaining budget for the 1.5°C target could be as low as 200 Gigatons of CO2, which is in stark contrast to the 4.000 Gigatons of CO2 that would be emitted if current trends continue. Mitigation efforts pledged so far are inadequate to reduce emissions sufficiently. This gives rise to concerns about the increasing reliance on uncertain and potentially risky technologies for so-called negative CO2 emissions, pulling greenhouse-gases out of the atmosphere by scaling up for instance bioenergy plantations or carbon capture and storage (CCS).