Variation in methodology obscures clarity of cropland global warming potential estimates

Global warming potential (GWP) estimates from agroecosystems are valuable for understanding management effects on climate regulation services. However, GWP estimates are complex, including attributes with high spatiotemporal variability. Published GWP estimates from cropland were compiled and methodological attributes known to influence GWP were extracted. Results revealed considerable variation in approaches to estimate GWP. Among carbon balance methods, respiration methods were used most frequently (33%), followed by soil carbon stock change over time (30%). Twenty-six percent of studies did not account for carbon change in GWP estimates. Duration of gas flux measurements ranged from 0.5 to 60 months, with weekly and sub-weekly sampling most common (34% and 33%, respectively). Carbon dioxide equivalent conversion factors generally aligned with Intergovernmental Panel on Climate Change recommendations through 2014 but diverged thereafter. This review suggests the need for increased transparency in how GWP estimates are derived and communicated. Presentation of key metadata alongside GWP estimates is recommended.

Automated summary

Global warming potential (GWP) estimates from agroecosystems are complex and highly variable due to the various attributes involved. A review of published GWP estimates from cropland revealed considerable variation in estimation approaches, with respiration methods and soil carbon stock change being the most commonly used methods. Furthermore, there was a lack of consistency in accounting for carbon change in GWP estimates and a divergence in carbon dioxide equivalent conversion factors in recent years. This review highlights the need for increased transparency and presentation of key metadata alongside GWP estimates.