L19: GCAM-E3SM CO2 coupling and land results

GCAM-E3SM atmosphere coupling progress and land coupling results

• Dalei Hao

• dalei.hao@pnnl.gov

Tim Shippert, Alan Di Vittorio, Eva Sinha, and Ben Bond-Lamberty

‘Land - River - Human’

E3SM

The full GCAM-E3SM coupling with active atmosphere and land is nearing completion. GCAM annual, regional CO₂ emissions are downscaled to a spatial grid at monthly time intervals and then passed to EAM via the coupler at the beginning of each year. Two downscaling methods are being explored: 1) a simple linear scaling based on base-year gridded emissions and 2) a more detailed downscaling that further adjusts future spatial patterns based on the assumption of convergence over time of national emission intensity (i.e., emission per GDP) to the regional average. These methods produce similar results overall, but method 1 may produce unrealistic results when there are big differences among countries within the same region, while method 2 explicitly considers the dependence of country-level CO₂ emissions to future population growth and income levels. GCAM outputs both surface and aircraft CO₂ emissions, and the IAC model component disaggregates the aircraft emissions into multiple vertical layers for input to EAM. The GCAM-ELM full feedback coupling is fully implemented and preliminary results indicate that the land use projection is sensitive to terrestrial productivity feedbacks on crop yields.

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