Splitting Anthropogenic and Biomass Burning Sources of Organic Carbon in GOCART-2G

Splitting Anthropogenic and Biomass Burning Sources of Organic Carbon in GOCART-2G

Authors: Allie Collow, Joe Ardizzone

Editors: Bennett Erdman

Published February 19, 2026

For the past few years, NASA's GMAO has been integrating a new version of the aerosol module, Goddard Chemistry Aerosol Radiation and Transport (GOCART), into its operational products. The upgrade from GOCART to GOCART Second Generation (GOCART-2G) required years of development and testing, and incorporates a refactored code, science updates, and the selection of more modern emissions datasets. We are pleased to announce that the hard work has come to fruition with the release of GOCART-2G in GEOS FP 5.43.

The biggest science change, and therefore impact on the user community, is the split of organic carbon into its components from anthropogenic and biomass burning sources. At smaller wavelengths, organic carbon emitted by biomass burning is more absorbing than organic carbon from anthropogenic sources, and this distinction is now represented by GOCART-2G. New diagnostics have been added, and referred to as brown carbon, to represent the contribution of organic carbon from wildfire smoke and processes controlling brown carbon aerosol. The anthropogenic portion of organic carbon is still referred to as organic carbon.

Figure 1: Aerosol optical depth associated with organic carbon, brown carbon, and sea salt from a GEOS simulation with GOCART-2G at 0z on 28 August 2025. Orange shading indicates where there is brown carbon (smoke) while green shading depicts organic carbon associated with anthropogenic emissions.

An example of this new speciation can be seen in the animation below and still image above for late summer of 2025. The orange shading depicts aerosol optical depth due to brown carbon, or the portion of organic carbon affiliated with biomass burning. Wildfires are typically prevalent during the boreal summer months across Canada, central Africa, and Siberia though this period was a relatively mild for Siberia. Smoke emitted by wildfires can travel hundreds of miles, having far reaching impacts. The green shading is organic carbon emitting by anthropogenic sources such as the combustion of fossil fuels for energy production or transportation. Within GEOS, anthropogenic emissions are released in the lowest model level for non-energy sources and emissions from energy sources are released at a height akin to the tower of a power plant. This allows anthropogenic emissions to stay closer to the surface, and therefore closer to the source compared to wildfire smoke. In the animation, organic carbon is maximized near cities around the globe, though higher values of aerosol optical depth are evident in India and China.