Recent Interannual Variations in Exchanges of CO2 with the Atmosphere: Inverse Model Results and Consistency with Bottom-up Approaches

We have inferred regional biospheric and oceanic exchanges of CO2 with the atmosphere by an inverse calculation from measurements of the concentration and C13/C12 isotopic ratio of atmospheric CO2. Over the last 20 years, tropical biospheric fluxes have been primarily responsible for El Nino scale variations in atmospheric CO2. The magnitude We have inferred regional biospheric and oceanic exchanges of CO2 with the atmosphere by an inverse calculation from measurements of the concentration and C13/C12 isotopic ratio of atmospheric CO2. Over the last 20 years, tropical biospheric fluxes have been primarily responsible for El Nino scale variations in atmospheric CO2. The magnitude and timing of biospheric fluxes from our inversion are only broadly consistent with results from terrestrial biospheric process models. However, in order to reliably predict future changes in atmospheric CO2, we must accurately characterize the role of biological processes which requires agreement between the atmospheric inverse calculation and biospheric models. We will present results from a biological model and an examination of the the spatial and temporal patterns of primary climate drivers and of new time series of the satellite greenness index, NDVI, as a step towards resolving current discrepancies between the "top-down" and "bottom-up" estimates of biological CO2 fluxes.