Significance Statement
Gross
primary production (GPP), the amount of carbon fixed during
photosynthesis in a given length of time, is the fuel of life and one of
the key components of the global carbon cycle.
Although numerous efforts have
been made to estimate GPP at the global scale, its uncertainty has
remained high for decades. It is necessary to evaluate the performance
of relevant models and supporting datasets against high-quality field
measurements to find out where the loose parts are, and then tighten the
loose ends. Our study reveals that
large biases exist in some of the models and driving spatial data
products, and addressing these biases is a high priority in modeling GPP
from site to global scales.