This looks like a steep number for me – 31 Gt CO2 (8.4 GtC). In my UNEP publication “Putting Carbon back where it belongs – the potential of carbon sequestration in the soil” (probably published under the head of the division, Jacqueline McGlade, see below), estimates are more in direction of 7.5-11 Gt CO2.
Using better farming techniques to store 1% more carbon in about half of the world’s agricultural soils would be enough to absorb about 31 gigatonnes of carbon dioxide a year, according to new data. That amount is not far off the 32 gigatonnes gap between current planned emissions reduction globally per year and the amount of carbon that must be cut by 2030 to stay within 1.5C.
The estimates were carried out by Jacqueline McGlade, the former chief scientist at the UN environment programme and former executive director of the European Environment Agency. She found that storing more carbon in the top 30cm of agricultural soils would be feasible in many regions where soils are currently degraded.
McGlade now leads a commercial organisation that sells soil data to farmers. Downforce Technologies uses publicly available global data, satellite images and lidar to assess in detail how much carbon is stored in soils, which can now be done down to the level of individual fields.