资源环境科技发展态势分析平台

Methyl bromide (CH₃Br) is an ozone depleting trace gas that is now mainly emitted from natural sources. Roughly 80% of anthropogenic production of CH₃Br was phased-out in response to the Montreal Protocol on Substances that Deplete the Ozone Layer beginning in 1999 and atmospheric levels of CH₃Br have declined considerably since. Here we use surface measurements of CH₃Br from NOAA’s global air sampling network, along with a six-box atmosphere/ocean model to explore interannual variability in atmospheric CH₃Br mole fractions. We find that CH₃Br mole fractions are strongly correlated with the El Niño Southern Oscillation (ENSO) phenomenon, but variability in winds, SST, and biological production during ENSO are unlikely to drive the observed changes in atmospheric CH₃Br directly. Rather, the results indicate that ENSO-driven changes to biomass burning are an important cause of the observed interannual CH₃Br variability.