The dilemma of the dwarf Earth's CO2 degassing: Irrelevant or crucial?

Abstract

The role of Earth's CO2 degassing is often confined to the definition of its limited absolute value and considered irrelevant to the global CO2 emission budget. Results reported in literature are contradictory leading to the evidence that the global Earth's CO2 degassing, independently from its absolute value, is virtually unknown. Global estimates are inconsistent with point source volcanic degassing and with the new discovered diffuse degassing sources. In the last twenty years, global Earth's CO2 flux extrapolations increased with the number of measurements from 110 to 937Mt/yr. Updated addition of CO2 degassing measurements from less than 10% of recognized geological sources equals the mostly agreed global estimates. Careful analysis of data shows evidence of large uncertainties on the estimates of CO2 Earth's degassing, requiring a better understanding of the physical and geological mechanisms behind climate variability and of processes governing the global carbon cycle. Beside model uncertainties and stabilization scenarios, an unknown value of the natural Earth's emissions, with a distinctive C isotopic ratio, leads to inadequate parameterization of unsettled pivotal processes relevant to studies of the global carbon cycle, atmospheric processes, ocean and land uptake, air–sea exchanges, and mantle petrology and dynamics.