There has been a recent increase in awareness of the interactions between ozone depletion and climate change. The 2010 United Nations Environment Program (UNEP) assessment of the environmental effects of ozone depletion and its interactions with climate change concluded that projected changes in ozone and clouds may affect levels of ultraviolet (UV) radiation at the Earth’s surface (though the effects vary according to geographical location). Although the impact on skin cancer risk has not been a major focus of climate change research, changing levels of UV radiation and warming temperatures may affect skin cancer incidence.
According to the CSIRO and the Bureau of Meteorology, mean temperatures within Australia are projected to rise by 0.6 to 1.5°C by 2030 compared with the climate of 1980 to 1999. Warmer temperatures may result in Australians increasing their sun exposure and wearing less covering clothing, thereby increasing their risk of skin cancer. However, very high temperatures may instead prompt behaviours to avoid sun exposure, and therefore "there is considerable uncertainty in modeling future human behaviour in response to climate change". There is weak animal model evidence that higher ambient temperatures may increase the skin cancer-effective UV dose by a few percent per celsius, which would result in more skin cancers for the same level of UV radiation. However, this is highly speculative.
The increase in UVB levels due to stratospheric ozone depletion that has occurred may have contributed to the increasing skin cancer incidence rates in Australia since the 1970s. However, other factors, such as sun-seeking behaviour during the second half of the 20th century and an ageing population are also important. We do not know which of these has been most important or how much each contributes to the higher skin cancer incidence since the 1970s. Complete compliance with the Montreal Protocol is estimated to prevent two million skin cancer cases worldwide by 2030.
In Australia, small increases in UVB radiation of up to 5% have been observed since 1980. However, with implementation of the Montreal Protocol ozone recovery is expected. Ozone levels are expected to return to 1980s levels by mid-century in Australian states in the middle latitudes (all capital cities except Darwin). However, UV radiation levels are dependent on a variety of factors in addition to ozone levels and are sensitive to future changes in cloud cover and air pollutant/aerosol concentrations. These latter factors will be the most important modifiers of UV radiation on the Earth’s surface, in the future.
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