A Post-Phaseout Retrospective Reassessment of the Global Methyl Bromide Budget Academic Article uri icon

abstract

  • AbstractMethyl bromide is a stratospheric ozonedepleting substance with both natural and anthropogenic sources. The global budget of methyl bromide has never been fully understood as evidenced by the significant budget gap between the bottomup source estimates and calculated atmospheric losses. Atmospheric methyl bromide levels have declined significantly since Phaseout under the Montreal Protocol began in 1999, and the atmosphere appears to have reached a new steady state during the past five years. Here, we reassess the global methyl bromide budget utilizing the 25year record of atmospheric methyl bromide measurements from the National Oceanic and Atmospheric Administration Global Monitoring Laboratory global flask network and a zonal 6box coupled global ocean/atmosphere model. Model inversions were used to estimate the total emissions required to account for the observed atmospheric methyl bromide levels. From 1995 to 2019, global landbased emissions (natural and anthropogenic) declined from about 120 to 85Gg y1 and net ocean emissions increased from 5 to +5Gg y1. There remains an imbalance between the bottomup estimates of terrestrial sources and the inversion result. Based on the timing, magnitude, and spatial distribution of the imbalance we partition it into (a) a persistent or time invariant source located primarily in the tropics, and (b) a smaller timevarying component that scales with the anthropogenic source during phaseout. We hypothesize that the persistent source is likely natural and the time variant component is an artifact resulting from a slight underestimation of anthropogenic emissions.

published proceedings

  • JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES

altmetric score

  • 3

author list (cited authors)

  • Saltzman, E. S., Nicewonger, M. R., Montzka, S. A., & Yvon-Lewis, S. A.

citation count

  • 2

complete list of authors

  • Saltzman, ES||Nicewonger, MR||Montzka, SA||Yvon-Lewis, SA

publication date

  • February 2022