Methyl bromide is an important ozone depleting trace gas that is currently emitted primarily from natural sources. Most of the anthropogenic production of methyl bromide was phased out in response to Montreal Protocol on Substance that Deplete the Ozone Layer in 1999 and its atmospheric concentration has significantly declined since. However, the cause of a substantial temporary variation observed in the atmospheric concentration of methyl bromide remains elusive. A new study funded in part by CPO’s Atmospheric Chemistry, Carbon Cycle, & Climate (AC4) program and published in the journal of Geophysical Research Letters investigated the causes leading to the interannual variability of methyl bromide.
Researchers from NOAA’s Global Monitoring Lab and University of California, Irvine used surface measurements of methyl bromide from NOAA’s global air sampling network along with a multi-box atmospheric and ocean model to investigate how changing emissions from different sources affect the atmospheric mole fraction of methyl bromide over different regions. The findings suggest a strong correlation of the interannual variability of methyl bromide with El Niño Southern Oscillation (ENSO) events, and the increased biomass burning during the warm phase of ENSO is determined to be the most likely cause of these interannual changes. The results also indicate that the variability in winds, sea surface temperature, and biological production during ENSO do not directly drive the observed changes in atmospheric methyl bromide. Previous models suggest that climate change may increase the frequency of extreme El Niño events, enhancing the concentration of methyl bromide and its significant contribution to ozone depletion.
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For more information, contact Shiv Das.