Against Coherence: Truth, Probability, and Justification

Abstract

Previous studies have demonstrated the importance of enhanced vegetation\textbackslashngrowth under future elevated atmospheric CO2 for 21st century climate\textbackslashnwarming. Surprisingly no study has completed an analogous assessment\textbackslashnfor the historical period, during which emissions of greenhouse gases\textbackslashnincreased rapidly and land-use changes (LUC) dramatically altered\textbackslashnterrestrial carbon sources and sinks. Using the Geophysical Fluid\textbackslashnDynamics Laboratory comprehensive Earth System Model ESM2G and a\textbackslashnreconstruction of the LUC, we estimate that enhanced vegetation growth\textbackslashnhas lowered the historical atmospheric CO2 concentration by 85 ppm,\textbackslashnavoiding an additional 0.31 \textbackslashpm 0.06 \textbackslash,\textasciicircum\textbackslashcirc\C warming. We\textbackslashndemonstrate that without enhanced vegetation growth the total residual\textbackslashnterrestrial carbon flux (i.e., the net land flux minus LUC flux)\textbackslashnwould be a source of 65–82 Gt of carbon (GtC) to atmosphere instead\textbackslashnof the historical residual carbon sink of 186–192 GtC, a carbon\textbackslashnsaving of 251–274 GtC.