How is UV radiation level changing at the Earths surface?
Direct measurement of UV-B radiation levels is technically complicated. However, there is overwhelming scientific evidence that ozone depletion leads to more UV-B reaching the Earth’s surface, and that the amount of increase can be predicted from trends in ozone levels. On this basis, UV-B at mid-latitudes is calculated to have increased by 8-10 per cent over the last 15 years (the calculation is for UV-B radiation at a wavelength of 310 nanometres at latitudes 45 north and south over the period 1979-1994). Calculated increases in UV-B to date are larger at higher latitudes and for shorter wavelengths. The first persistent increase in UV-B over densely populated areas due to ozone depletion was measured in 1992/93. Several studies found large increases at northern mid and high-latitudes. Measurements at Toronto, Canada, suggested that UV-B at 300 nanometres was 35 per cent higher than four years previously. Large increases in UV-B have occurred in Antarctica due to the annual ozone hol
