A decline in tropospheric organic bromine

Abstract

Recent changes in atmospheric bromine (Br) are estimated from samples collected at ten globally distributed, ground‐based sites. The results indicate that the global tropospheric burden of Br from the sum of halons and methyl bromide (CH 3 Br) peaked in 1998 and has since declined by nearly 5% (or 0.8 ± 0.2 pmol mol −1 or ppt). These changes are driven primarily by a decrease of CH 3 Br since 1998 that is about two times larger than expected given reported declines in industrial production, a result that may suggest revisions to our understanding of the global atmospheric budget for this gas. The observations imply 25–30% larger declines in the atmospheric burden of ozone‐depleting, total equivalent chlorine (ECl = Cl + Br*45) in recent years than noted previously.