Ozone layer stratospheric wind patterns. In the northern hemisphere these patterns, known as the Brewer-Dobson circulation, make the ozone layer thickest in the spring and thinnest in the fall. When ozone in produced by solar UV radiation in the tropics, it is done so by circulation lifting ozone-poor air out of the troposphere and into the stratosphere where the sun photolyzes oxygen molecules and turns them into ozone. Then, the ozone-rich air is carried to higher latitudes and drops into lower layers of the atmosphere. Research has found that the ozone levels in the United States are highest in the spring months
Vienna Convention for the Protection of the Ozone Layer the European Union. While not a binding agreement, it acts as a framework for the international efforts to protect the ozone layer; however, it does not include legally binding reduction goals for the use of CFCs, the main chemical agents causing ozone depletion. The treaty's provisions include the international sharing of climate and atmospheric research to promote knowledge of the effects on the ozone layer. In addition, the treaty calls for the adoption of international agencies to assess the harmful effects of depleted ozone and the promotion of policies that regulate the production of harmful substances that influence the ozone