Substantial hysteresis in emergent temperature sensitivity of global wetland CH4 emissions.
Riley, William J.
Knox, Sara H.
Jackson, Robert B.
Campbell, David I.
Delwiche, Kyle B.
Desai, Ankur R.
Hemes, Kyle S.
Nature Communications; 4/15/2021, Vol. 12 Issue 1, p1-10, 10p
Wetland methane (CH4) emissions ( F C H 4 ) are important in global carbon budgets and climate change assessments. Currently, F C H 4 projections rely on prescribed static temperature sensitivity that varies among biogeochemical models. Meta-analyses have proposed a consistent F C H 4 temperature dependence across spatial scales for use in models; however, site-level studies demonstrate that F C H 4 are often controlled by factors beyond temperature. Here, we evaluate the relationship between F C H 4 and temperature using observations from the FLUXNET-CH4 database. Measurements collected across the globe show substantial seasonal hysteresis between F C H 4 and temperature, suggesting larger F C H 4 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. Wetland methane emissions contribute to global warming, and are oversimplified in climate models. Here the authors use eddy covariance measurements from 48 global sites to demonstrate seasonal hysteresis in methane-temperature relationships and suggest the importance of microbial processes. [ABSTRACT FROM AUTHOR]
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