Scientific Assessment of Ozone Depletion: 2018 - Executive Summary

This document summarizes the 2018 scientific assessment of ozone layer status and policy-relevant findings under the Montreal Protocol. It reports continued declines in controlled ozone-depleting substances and early recovery signals: the Antarctic ozone hole remains annual but shows signs of shrinking, upper-stratospheric ozone has increased by about 1–3% per decade since 2000, and near-global total column ozone shows no significant trend over 1997–2016, staying roughly 2% below 1964–1980 averages. An unexpected post-2012 rise in CFC-11 emissions is identified, and previously unrecognized sources of carbon tetrachloride are better quantified. The Kigali Amendment’s phasedown is projected to reduce HFC-related warming from roughly 0.3–0.5°C to less than 0.1°C by 2100. Models project ozone returning to 1980 levels in the Northern Hemisphere mid-latitudes in the 2030s, Southern Hemisphere mid-latitudes around mid-century, and Antarctic spring in the 2060s.