The following passage is adapted from a 2008 article.

Stratospheric ozone absorbs ultraviolet solar radiation and prevents it from reaching Earth's surface and boosting skin-cancer rates. In Antarctic springtime (September to early December), stratospheric ozone concentrations are low. Consequently, the stratosphere absorbs less ultraviolet radiation and is therefore much cooler. This, in turn, increases temperature differences between air over the mid-latitude Southern Hemisphere regions and air over Antarctica—differences that cause strong, steady winds called the circumpolar westerlies.

These winds have been strengthening in recent decades due to "the ozone hole"—the low polar-ozone concentrations arising from a decades-long decline. These strengthened winds have been preventing many storm systems that head south from temperate latitudes—as well as the large quantities of warm air they contain—from reaching central Antarctica. Recently, however, average Antarctic stratospheric ozone concentrations have been increasing. Research indicates that this recovery of the ozone layer, if sustained, would slow the circumpolar westerlies while strengthening other southern-hemisphere winds, a combination that would significantly shift weather patterns. Much of Australia would become drier, and portions of South America wetter. Moreover, if control of ozone-depleting substances brings about a full recovery of the Antarctic ozone layer, the average air temperature in Antarctica may be significantly higher.


The primary purpose of the passage is to


describe the effects of climate change on colder regions

specify the unintended consequences of efforts to control emissions of ozone into the atmosphere

explore the possible effects of a projected change in the atmosphere over Antarctica

argue for a reassessment of policies designed to curb damage to the ozone layer

evaluate the effects that certain changes in the Antarctic ozone layer would have on human health and climate

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