Scientific Assessment of Ozone Depletion: 2014

Chapter 3 Scientific Summary

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Scientific Summary Chapter 3: Polar Ozone: Past, Present, and Future

Polar Ozone Changes

As stated in the previous Assessments, ozone-depleting substance (ODS) levels reached a maximum in the polar regions around the beginning of this century and have been slowly decreasing since then, consistent with the expectations based on compliance with the Montreal Protocol and its Amendments and adjustments. Considering the current elevated levels of ODSs, and their slow rate of decrease, changes in the size and depth of the Antarctic ozone hole and in the magnitude of the Arctic ozone depletion since 2000 have been mainly controlled by variations in temperature and dynamical processes.

Understanding of Polar Ozone Processes

Since the last Assessment, new laboratory measurements have strengthened our knowledge of polar ozone loss processes. Simulations using updated and improved models have been tested using the wealth of currently available measurements from satellites, ground-based networks, and dedicated campaigns.

Future Changes in Polar Ozone

Projections of future ozone levels in this Assessment are mainly based on the CCM simulations used in the last Assessment. Individual studies using results from climate models provide new insights into the effects of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) on future polar ozone levels by the end of this century.