Suspect the study was based on temp increases generated by the MIT model a few years back. MIT advised me over a year ago that threir model needs to be updated to reflect the UNFAO/IPCC/NASA/DOE updated models which a few years back identified a fifty fold increase in our knowledge about the global flow units involved in determining our atmospheric CO2 level.  Please go the CARBON CYCLE DIAGRAM in google ..the updated models with their 430 GtC units of flow are right in front of your eyes. In the the early 2000's,  UNFAO/IPCC/NASA/DOE etal all believed that there were only 6 to 7 GtC units involved with fossil fuels being 6 GtC of those units. I am merely the messenger drawing your attention to the quantum change and highlighting how easy it is for you to access the updated models. There are more than 420 GtC units of flow in land and oceanic areas that were previously ignored. Fossil fuels are still 6 GtC  . The data is all from the innermost sanctum of climate change global orgs.