Moving from simple x-y comparisons to multiple constraint functional response analyses to improving carbon cycle predictability

A wide variety of vegetation models exist, all of which have been ‘validated’ using a broad range of ecosystem observations. When asked a question, however, they all give very different answers, particularly when the question relates to the future of the global carbon cycle. Important differences in the implementation of our process understanding, and parameterization, remain hidden due to the lack of rigorous approaches for model assessment. Here, I advocate for renewed emphasis on the use of multiple observational constraints, combined with analyses of functional responses, as a way to move the field closer to being an effective predictive science.