NASA's Goddard Institute for Space Studies has released ModelE2.1-CC2, an Earth system model that simulates how carbon moves through oceans, forests, and the atmosphere. The model builds on the previous CMIP6 version with upgraded ocean and land carbon cycles, tracking everything from phytoplankton activity to soil carbon storage. It was designed to answer a central climate question: where does the CO2 we emit actually end up, and will that change as the planet warms. The model matches observed atmospheric CO2 closely in historical runs from 1850 to 2021, and its soil carbon estimate of 1,693 petagrams is nearly identical to inventory data. The paper is open about weaknesses, including low ocean net primary productivity and overestimated forest biomass due to outdated lidar height data. Those issues are flagged for future versions, which will use NASA's GEDI and ICESat-2 data and add fire and deforestation modules. For anyone tracking carbon budgets or climate policy, this is a useful technical update. It shows how far model validation has come and where the remaining gaps are.
