Quantifying airborne fraction trends and the destination of anthropogenic CO2 by tracking carbon flows in a simple climate model

摘要: Atmospheric carbon dioxide (CO 2) concentrations have increased as a direct result of human activity and are at their highest level over the last 2 million years, with profound impacts on the Earth system. However, the magnitude and future dynamics of land and ocean carbon sinks are not well understood; therefore, the amount of anthropogenic fossil fuel emissions that remain in the atmosphere (the airborne fraction) is poorly constrained. This work aims to quantify the sources and controls of atmospheric CO 2, the fate of anthropogenic CO 2 over time, and the likelihood of a trend in the airborne fraction. We use Hector v3. 0, a coupled simple climate and carbon cycle model with the novel ability to explicitly track carbon as it flows through the Earth system. We use key model parameters in a Monte Carlo analysis of 15 000 model runs from 1750 to 2300. Results are filtered for physical realism against historical …