The 50-Year CO₂ Balance: Crucial Roles of Agriculture, Forestry and the Ocean

CO₂ exchanges between continents, oceans and atmosphere are analyzed over the last 50 years, correcting for the importance of agriculture and forestry. To do this, we simply considered their commercial production statistics and their 40 to 50% of dry weight carbon content. These vital activities have captured on average 39.9 GtCO₂/year from the atmosphere over the last decade. This carbon capture and storage (CCS) by plants has more than doubled since 1970 and compensated for 36.0 GtCO2/year of fossil emissions. After mineralization by respiration and combustion, the carbon mobilized in those biomasses returned to the atmosphere as CO2 . This release, which takes a quarter of a century after harvest on average, has stabilized at around 10.2 GtCO₂/year over the last half-century, leading to a continental balance, including the combustion of fossil hydrocarbons, of 6.8 GtCO₂/year emitted on average. Contrary to what is generally accepted, CCS by plant cultivation has completely offset emissions from the combustion of fossil hydrocarbons. As a result of this new balance, the ocean appears to have been an increasingly important source of CO₂, going from neutral in the 1970s to an average of 10.6 GtCO₂/year over the last decade. Over the half-century, the ocean has contributed 52% to the increase in atmospheric CO₂ concentration, with the remainder coming from the continents