Surprised by Simplicity: Model Experiments Reveal Rule of Thumb for Carbon-Climate Dynamics

Together, the land vegetation and the ocean take up approximately half of anthropogenic carbon emissions, thereby keeping that fraction out of the atmosphere and mitigating human-induced climate change. But how much longer will this invaluable service be provided, and how much warmer will it get when their ability to absorb carbon declines? Scientists use complex Earth system models to answer these questions. A team of researchers led by the Max Planck Institute for Meteorology (MPI-M) has derived useful, easy-to-use approximations from such model experiments that can be evaluated with paper and pencil. These approximations help draw general conclusions about how atmospheric carbon dioxide evolves with further increasing carbon emissions and about the implications for global warming.

The team used idealized model experiments that examined what would happen if fossil fuel emissions remained at 10 PgC/year—the current emission level—over 100 years and then slowly reversed to 10 PgC/year carbon removal from atmosphere within the next 200 years. By analyzing the results, MPI-M researchers Victor Brovkin, Noel Brizuela, Tatiana Ilyina and Hongmei Li, in collaboration with colleagues from several international climate modeling groups, found that accumulated carbon uptake on land and in the ocean increase proportionally for most Earth system models analyzed.

“This was surprising, as carbon uptake on land and in the ocean are driven by very different processes. On land, carbon uptake is governed by biological processes such as photosynthesis and microbial respiration, while in the ocean, the chemical uptake of carbon dominates”, explained lead author Victor Brovkin.