When it's winter in the north and summer in the south, many cold-weary tourists from Europe and North America flock to New Zealand for its wild backcountry and radiant sunshine. They may be getting more than they bargained for, according to a report  in tomorrow's issue of Science. Over the past 10 years peak levels of skin-frying and DNA-damaging ultraviolet (UV) rays have gradually been increasing in New Zealand, just as concentrations of protective stratospheric ozone have decreased.
Scientists first detected the notorious "ozone hole" over the South Pole 14 years ago, the apparent result of chemical reactions caused by chlorofluorocarbons and other pollutants in the stratosphere. Ever since, their calculations have predicted that loss of stratospheric ozone--which acts like a protective sheath around the planet, absorbing much of the harmful UV-B radiation--would let through more of the rays. And not just in the sparsely populated polar regions: In the 1980s, researchers began to realize that stratospheric ozone was also thinning above populous midlatitude regions such as northern Europe, Canada, New Zealand, and Australia.
Now, a team led by atmospheric scientist Richard McKenzie of the National Institute of Water and Atmospheric Research in Lauder, New Zealand, has come up with data that appear to clinch the connection between ozone and UV-B in the midlatitudes. In measurements taken each year since 1989 in Lauder, a rural region on New Zealand's South Island that enjoys unpolluted, cloudless days much of the year, the researchers have found that maximum summertime UV-B levels crested higher and higher until they are now at least 12% above what they were at the beginning of the study. That agrees remarkably well with the roughly 15% increase the researchers had predicted based on the known decline in stratospheric ozone levels measured since 1978 in Lauder. Meanwhile, the longer wavelength UV-A radiation, which is unimpeded by ozone, remained relatively constant.
Experts say the study provides the strongest evidence yet that a degraded stratospheric ozone layer causes more hazardous conditions for life on the planet's surface. "They have done about as careful a study as you can do," says atmospheric physicist Paul Newman of Goddard Space Flight Center in Greenbelt, Maryland. New Zealand's peak UV-B levels could put the country's inhabitants at increased risk of skin cancer, cataracts, and perhaps immune system suppression. But McKenzie notes that the country still gets less UV radiation than unpolluted low-latitude regions of Africa, Australia, and South America.