Against Coherence: Truth, Probability, and Justification

Abstract

Previous studies have demonstrated the importance of enhanced vegetation\ngrowth under future elevated atmospheric CO2 for 21st century climate\nwarming. Surprisingly no study has completed an analogous assessment\nfor the historical period, during which emissions of greenhouse gases\nincreased rapidly and land-use changes (LUC) dramatically altered\nterrestrial carbon sources and sinks. Using the Geophysical Fluid\nDynamics Laboratory comprehensive Earth System Model ESM2G and a\nreconstruction of the LUC, we estimate that enhanced vegetation growth\nhas lowered the historical atmospheric CO2 concentration by 85 ppm,\navoiding an additional 0.31 \pm 0.06 ,^\circ\C warming. We\ndemonstrate that without enhanced vegetation growth the total residual\nterrestrial carbon flux (i.e., the net land flux minus LUC flux)\nwould be a source of 65–82 Gt of carbon (GtC) to atmosphere instead\nof the historical residual carbon sink of 186–192 GtC, a carbon\nsaving of 251–274 GtC.