A decline in tropospheric organic bromine

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 (CH3Br) 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 CH3Br 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.