storage. We identify five primary research imperatives for atmospheric chemistry in global change research—the research imperatives presented in the opening paragraphs of this chapter. With these disciplinary imperatives come infrastructure initiatives, without which the research cannot be executed. Lessons extracted over the past four decades of research provide substantial guidance for such infrastructure initiatives.

CASE STUDIES

This section describes selected scientific cases that led to diagnoses central to studies of global change. In describing these developments attention is given to the ways that such transitions in our scientific thinking can be linked to specific public policy initiatives and to how such cases have been related to both environmental decisions and technological developments. Thus, we address the questions: Why is it in the national interest to pursue this research? Are there links between this research and economic competitiveness?

The Antarctic Ozone Hole

Discovery and diagnosis of the Antarctic Ozone Hole were a major surprise for both scientists and the public policy structure. In worldwide studies extending back to the 1950s, the amount of ozone over the Antarctic was tracked each year through its seasonal cycle. In the late 1970s an anomalous deficit was observed in total ozone amount in the late-winter observations. In 1985 the British Antarctic Survey reported for the first time in the scientific literature2 that dramatic losses were occurring in the ozone concentration over Halley Bay and that the degree of ozone loss was worsening as the decade progressed. Theories about the cause of this unprecedented loss blossomed. Explanations ranged from simple redistribution by atmospheric motion to chemical reactions initiated by magnetic field focusing of solar electrons and protons. Such theories were put forward by serious scientific research groups in an international effort to diagnose the cause of this unexpected development.

A number of expeditions were planned to gather more complete information. In 1986 NASA planned an airborne expedition using the ER-2 aircraft to penetrate the region of the stratosphere where ozone was disappearing. The mission, executed in August and September 1987 from Punta Arenas, Chile, and supported by concurrent laboratory and modeling studies, demonstrated unequivocally that ozone was destroyed by chlorine and bromine radicals (see Figure 5.1). The role of chlorofluorocarbons (CFCs)—the molecules that transport chlorine to the stratosphere—in the destruction of ozone over the Antarctic rests on three discoveries from the NASA mission.3 The first discovery was that the region of severe ozone depletion was isolated from the rest of the stratosphere by the polar night jet that defines the perimeter of the Antarctic vortex. This isolation creates



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