By virtue of its multiple important impacts on climate, air quality, and human, animal and environmental health, ozone is arguably one of the most important trace gases in the atmosphere. Elevated ozone near the earth’s surface contributes to poor air quality, with impacts on humans, the biosphere, and agriculture. As such, maximum allowable surface-level concentrations are regulated in many countries. In addition, ozone is radiatively active and thus is treated as a climate-relevant gas that contributes to and responds to climate change. In the stratosphere, ozone serves as the “sunscreen” for the world by shielding the earth’s surface from harmful ultraviolet radiation. Throughout the atmosphere, ozone is the key ingredient that initiates chemical cleansing of the atmosphere of various pollutants. These multiple roles, which depend on the location of ozone in the atmosphere, present a challenge to clearly communicating ozone’s regional and global significance, and to developing clear recommendations for mitigating its negative impacts.
Since the previous AMS statement was issued, there has been significant progress in recognizing the multiple roles of atmospheric ozone, in understanding the precursors that lead to ozone formation and its long-range transport and impacts, and in identifying the reasons for trends in ozone in different parts of the atmosphere. Further, society has taken concerted actions to mitigate the negative impacts of ozone trends - the depletion of ozone in the stratosphere and increases of ozone in the troposphere – and these actions have produced significant results in some regions. Indeed, there are clear signs of progress in moving ozone abundances towards their natural levels. International cooperation in responding to the challenge of stratospheric ozone depletion remains one of the great scientific success stories of the twentieth century. However, in spite of progress in some regions, ozone changes are still a growing and significant environmental problem in others. There is much that needs to be done to continue on the path to mitigate ozone changes across the world - be it in regions where these are an increasing problem or in regions where gains have been made.
The American Meteorological Society is well positioned to contribute a clear, concise and compelling statement to assist the public and policy makers in understanding the current status of atmospheric ozone and the reasons and science behind calls to action. It is appropriate that the American Meteorological Society revise our information statement to reflect the advances in knowledge that have occurred over the past decade, as well as the progress that has been made in mitigating stratospheric ozone loss and tropospheric ozone pollution. Despite this progress, challenges remain. The challenges that remain must be clearly summarized along with an outlook for the future, and the potential policy options to address these challenges updated.