Global climate change is occurring due to the accumulation of greenhouse gases (CO2, methane, CFCs, and others) and loss of natural carbon sinks, leading to enhancement of the natural greenhouse effect that maintains Earth's temperature. There are a number of possible interactions between climate change and ozone depletion. First, several of the anthropogenic ozone-depleting gases, for example, CFCs are also greenhouse gases. Second, one effect of global climate change is projected to be global warming of the order of between 0.6 and 4 °C by 2050. Tropospheric warming induces stratospheric cooling, which, in turn, enhances free radical formation and ozone destruction. Loss of ozone itself augments stratospheric cooling (recall that a by-product of blocking UVB is production of heat), further enhancing the catalytic destruction of ozone.
Alternatively, there is considerable evidence that tropospheric aerosols and air pollutants such as ozone can attenuate UVB, but may also scatter UVR, redistributing incoming radiation from direct to diffuse radiation. Although this has little effect on levels of measured ambient UVR, it may increase UV exposure in locations shaded from direct sunlight.
Increasing global temperatures as a result of climate change may encourage a change in sun exposure behavior, for example, more sunbathing in temperate climates. Changes in cloud cover and precipitation will be very variable across regions and may also influence sun exposure behavior and thus personal UV dose.
Animal studies suggested many years ago that higher ambient temperatures may enhance the development of skin cancers. Recent work has shown that there is a trend toward a similar effect in human studies, where there is higher incidence of nonmelanoma skin cancers at locations with similar UVB levels but higher ambient temperature. Similar work in relation to nuclear cataract suggests that higher ambient temperatures may also increase risk of cataract for any level of ambient UVR.