October 1, 2017.
The global atmospheric methane burden approached equilibrium from 1983 until 2006, after which there was an increase in the rate of change that’s been sustained since then. It’s uncertain if this change was due to an increase in emissions, or a decrease in the rate of sink, or a combination of both. Our method attempted to provide evidence to show whether or not this change was due to a decrease in the sink, corresponding to an increase in the lifetime of methane. A one-box model of methane was employed to determine what the lifetime of methane would need to be each year if emissions were held constant. The primary loss mechanism for methane is the same for carbon monoxide: reactions with hydroxyl radicals. If there was a change in the sink for methane, it’s very likely that this would be due to a change in the concentration of hydroxyl. It was shown that the corresponding change in carbon monoxide concentrations would be insignificant compared to the variability of the observations. This insignificant change renders our method inconclusive.
National Oceanic Atmospheric Administration Earth Systems Research Laboratory (NOAA ESRL)
This material is based upon work supported by the National Science Foundation through the Robert Noyce Teacher Scholarship Program under Grant # 1340110. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. The research was also made possible by the California State University STEM Teacher and Researcher Program, in partnership with Chevron (www.chevron.com), the National Marine Sanctuary Foundation (www.marinesanctuary.org) and NOAA Earth System Research Laboratory.