Invited Speaker Skin Cancer 2024

What's so different about our UV radiation? Past changes and future projections (#2)

Richard McKenzie 1
  1. NIWA, Lauder, CENTRAL OTAGO, New Zealand

Skin cancer rates in Australia and New Zealand are the highest in the world - by a comfortable margin.  This presentation addresses several related questions about those high rates. Is it because of our proximity to the Antarctic ozone hole? How much does ambient UV contribute to this statistic? How much have ozone changes in recent decades contributed to it? And how do we expect changes in UV to affect it in the decades ahead? The ways UV information is estimated and reported to the public are discussed, along with their strengths and weaknesses. Measurements of sunburning UV radiation, and calculations using satellite-derived ozone are used to show that while UV in the southern hemisphere is relatively intense compared with corresponding latitudes in the northern hemisphere, the peak values in heavily-populated areas of Australasia are much less than over much of the tropics, especially at high altitudes. However, UV doses experienced in New Zealand and Australia do far exceed those appropriate for the skin-types of many. For example, UV doses in the British Isles, the ancestral homeland of many Australians and New Zealanders, are far below those experienced down-under. The main reason for that difference is the higher sun elevations experienced at lower latitudes. But inter-hemispheric differences in air quality, cloud-cover, ozone, and Sun-Earth separation in summer are also important. Long-term data shows that, while UV increases have been large in Antarctica, any have been small in populated areas. That finding is a testament to the success of the Montreal Protocol on Protection of the Ozone Layer. Future changes in UV are highly uncertain. Reductions in aerosol extinctions, and changes in cloud cover, both of which are related to climate change and our attempts to control it, will probably outweigh effects due to future changes in ozone. Unfortunately, the database for monitoring those changes is limited (and diminishing).