The NASA Carbon Monitoring System (CMS) Flux Pilot Project as a Means to Evaluate Global Land Surface Models

NASA's Carbon Monitoring System (CMS) Flux Pilot Project provides global land-atmosphere CO2 fluxes, among other products, constrained by the full suite of land, ocean, and atmosphere satellite remote sensing capabilities available with respect to the carbon cycle. We use the CMS CO2 fluxes to compare to 23 land surface models: 9 from the TRENDY model intercomparison project (run globally), and 14 from the NACP Regional Synthesis (run over N. America). The CMS fluxes also provide quantified uncertainties and represent an accurate bound with which the bottom-up land surface models should reside within. As such, we are able to pinpoint which land surface models exceed the limits of uncertainty and observational bounds. The CMS project is still in development so we make no conclusions as to model "skill" relative to CMS. In general, most models were able to capture the mean annual global averaged CO2 flux, but when disaggregating to finer scales of space and time, differences greatly increased.