Substantial hysteresis in emergent temperature sensitivity of global wetland CH4 emissions

Authors: CHANG, KUANG-YU - Lawrence Berkeley National Laboratory; WILEY, WILLIAM - Lawrence Berkeley National Laboratory; KNOX, SARAH - University Of British Columbia; JACKSON, ROBERT - Stanford University; MCNICOL, GAVIN - Stanford University; POULTER, BENJAMIN - Goddard Space Flight Center; AURELA, MIKA - Finnish Meteorological Institute; BALDOCCHI, DENNIS - University Of California, Davis; BANSAL, SHEEL - Us Geological Survey (USGS); BOHRER, GIL - The Ohio State University; Reba, Michele

Submitted to: Nature Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2021
Publication Date: 4/15/2021
Citation: Chang, K., Wiley, W.J., Knox, S.H., Jackson, R.B., Mcnicol, G., Poulter, B., Aurela, M., Baldocchi, D., Bansal, S., Bohrer, G., Reba, M.L. 2021. Substantial hysteresis in emergent temperature sensitivity of global wetland CH4 emissions. Nature Communications. 12(2266). https://doi.org/10.1038/s41467-021-22452-1.
DOI: https://doi.org/10.1038/s41467-021-22452-1

Interpretive Summary: Improving our understanding of greenhouse gas emissions are important in global carbon budgets and climate change assessments. Global measurements of methane emissions in wetland environment were gathered. The relationship between methane emissions and temperature was evaluated. Seasonal hysteresis between methane emissions and temperature was shown in the analysis that used machine learning and regression modeling. Findings highlight the importance of large-scale analysis across multiple years and ecosystem types. Findings benefit modelers and those interested in improving understanding of global carbon markets and climate change assessments.

Technical Abstract: Wetland methane (CH4) emissions (FCH4) are important in global carbon budgets and climate change assessments. Currently, FCH4 projections rely on prescribed static temperature sensitivity that varies among biogeochemical models. Meta-analyses have proposed a consistent FCH4 temperature dependence across spatial scales for use in models; however, sitelevel studies demonstrate that FCH4 are often controlled by factors beyond temperature. Here, we evaluate the relationship between FCH4 and temperature using observations from the FLUXNET-CH4 database. Measurements collected across the globe show substantial seasonal hysteresis between FCH4 and temperature, suggesting larger FCH4 sensitivity to temperature later in the frost-free season (about 77% of site-years). Results derived from a machine-learning model and several regression models highlight the importance of representing the large spatial and temporal variability within site-years and ecosystem types. Mechanistic advancements in biogeochemical model parameterization and detailed measurements in factors modulating CH4 production are thus needed to improve global CH4 budget assessments.