Scientists highlight mismatch in land-use emissions estimates

As the urgency to meet global climate goals intensifies, a new Comment published in Nature Sustainability underscores the need to reconcile how countries and global modelers account for land-use CO₂ emissions and removals. The paper, led by Giacomo Grassi and co-authored by LMU’s Julia Pongratz and Clemens Schwingshackl among others, identifies a 7-billion-tonne annual gap between national greenhouse gas inventories and global scientific models—equivalent to 20% of global fossil CO₂ emissions. This mismatch stems from differing definitions of what constitutes anthropogenic land-use change and has critical implications for tracking progress under the Paris Agreement.

Global models, which inform decarbonization pathways, typically include only direct human-induced effects, such as deforestation, reforestation and other anthropogenic land-use changes. National inventories, however, often count indirect effects—like CO₂ uptake from elevated atmospheric concentrations or fertilization effects from nitrogen deposition—and even natural variability from climate events like droughts and wildfires. Adding to the complexity, inventories rely on the concept of “managed land” as a proxy for human influence. Yet what is considered “managed” varies widely among countries, with some—including large, forested nations—classifying nearly all land as managed, while others exclude vast areas. This inconsistency means inventories may attribute more CO₂ removals to human action than global models do.

The paper outlines a way forward: closer integration between global modelling, national reporting, and Earth observation communities. By developing common translation frameworks and increasing data transparency, countries can better align their climate action with the scientific understanding of the carbon cycle. “Bridging this gap is crucial,” says Julia Pongratz, “if we are to assess mitigation efforts fairly and meet the temperature goals of the Paris Agreement.”