Simulating the land carbon sink: Progresses and challenges of terrestrial ecosystem models

Terrestrial ecosystems play an important role in regulating the balance of global carbon cycle by sequestrating CO₂ of atmosphere. Terrestrial ecosystem models are a critical tool for quantifying the magnitude, interannual variability and long-term trends of the land carbon sink across various spatial and temporal scales; however, despite extensive research, large uncertainties and challenges still persist. This review first summarizes decades of history in ecosystem model development in terms of model theory and methods. We then identify model uncertainties, including those arising from model algorithms, parameterization and forcing data. Finally, we propose new opportunities to improve ecosystem models for accurately simulating the land carbon sink, including emerging process-based knowledge from observations and big data, as well as model-data fusion methods.