Using observations to evaluate terrestrial biosphere models on large scales

What is it about?

This study uses observations of quantities emitted and/or absorbed by the terrestrial biosphere as observational constraints on the processes of gross primary productivity and ecosystem respiration. The objective of this study is to try to provide a constraint on the seasonal cycle of gross primary productivity and ecosystem respiration in the northern midlatitudes which can be used to evaluate terrestrial biosphere models against. We find that the seasonal cycle of respiration simulated by a number of models has systematic differences from the seasonal cycle constrained by observations, suggesting that there may be systematic errors in model parameterizations.

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Why is it important?

Terrestrial biosphere models are important for predicting how much CO2 the terrestrial biosphere will absorb or release under increased atmospheric CO2 and climate change. However, these models currently disagree with each other on whether the terrestrial biosphere will be a sink or source of atmospheric CO2 in the future. This study is important because it provides an observationally constrained seasonal cycle of sources/sinks of CO2 against which terrestrial biosphere models can be evaluated. Differences between the observationally constrained seasonal cycle and modeled seasonal cycle will give insights into sources of model errors.