An Analysis of GWPbio and the Effects of Scale (WP-20-07)

A variety of methods and metrics have been proposed to quantify the impacts of biogenic CO₂ emissions. Most consider biogenic CO₂ in the context of the biogenic carbon cycle, recognizing that this cycle requires that biogenic CO₂ be differentiated from fossil CO₂. One of the metrics receiving attention is GWP_bio (Cherubini et al. 2011).

The GWP_bio metric provides a plot-level means for incorporating the biogenic carbon cycle into estimates of the global warming impact of biogenic CO₂ emissions.

This white paper examines the assertion that plot- and landscape-scale approaches are equivalent (and hence that use of GWP_bio can be reconciled with a landscape approach). The authors test the use of GWP_bio under several scenarios and discuss challenges in its application. The white paper concludes that, although the metric provides useful information and can be easily calculated for simple scenarios, it contains several embedded assumptions and conventions that (a) have large impacts on results and (b) may be inappropriate in several contexts.

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