Update on Ozone-Depleting Substances (ODSs) and Other Gases of Interest to the Montreal Protocol

Abstract

This chapter concerns atmospheric changes in ozone-depleting substances (ODSs), such as chlorofluorocarbons\n(CFCs), halons, chlorinated solvents (e.g., CCl<sub>4</sub> and CH<sub>3</sub>CCl<sub>3</sub>) and hydrochlorofluorocarbons (HCFCs), which are\ncontrolled under the Montreal Protocol. Furthermore, the chapter updates information about ODSs not controlled\nunder the Protocol, such as methyl chloride (CH<sub>3</sub>Cl) and very short-lived substances (VSLSs). In addition to depleting\nstratospheric ozone, many ODSs are potent greenhouse gases.<br/><br/>\nMole fractions of ODSs and other species are primarily measured close to the surface by global or regional monitoring\nnetworks. The surface data can be used to approximate a mole fraction representative of the global or hemispheric\ntropospheric abundance. Changes in the tropospheric abundance of an ODS result from a difference between\nthe rate of emissions into the atmosphere and the rate of removal from it. For gases that are primarily anthropogenic\nin origin, the difference between northern and southern hemispheric mole fractions is related to the global emission\nrate because these sources are concentrated in the northern hemisphere. [...]