Exposure to ultraviolet (UV) sunlight has positive and negative effects on human health, but importantly for New Zealand, contributes to our high rates of the skin cancer melanoma.
In this chapter, we consider stratospheric ozone, which absorbs UV sunlight and is important in controlling the levels of UV sunlight that reach Earth’s surface. We report on the global production of ozone-depleting substances, the changing state of the ozone hole, and ozone concentrations over New Zealand. With the successful phasing out of ozone-depleting substances through the 1987 Montreal Protocol (see box 8), a gradual recovery of ozone is expected in the years ahead (McKenzie et al, 2011).
Pressure on the atmosphere from ozone-depleting substances is now well-managed, but this is not the end of the story. Natural influences on New Zealand’s UV levels – for example, the natural seasonal variability in the ozone layer – help explain why our UV levels fluctuate during the year. Understanding these influences can help us to make good decisions on our exposure to UV sunlight.