Sunburn is caused by exposure of UV light. UVB and UVA rays penetrate the skin causing redness, itching and irritation. There are three key factors that cause us Kiwis to burn more than our friends on the other side of the world.
The first key factor is the way in which the Earth orbits the Sun. Most people do not know that the Earth orbits the Sun in an ellipse, not a circle. As the Earth orbits the Sun it experiences the closest point of approach in December and January, which is the southern hemisphere of summer. The furthest away is in June and July, which is the northern hemisphere summer.
Image courtesy of: https://theconversation.com/
Another reason is the ozone layer which is a thin part of the Earth's atmosphere that absorbs almost all of the sun's harmful ultraviolet light. During the summer months, there is a lot less ozone in the southern hemisphere than in the northern hemisphere. Because ozone is generated at the equator, it gets transported to higher latitudes, and due to ozone-depleting substances, a hole formed over Antarctica. The ozone layer sits in the upper atmosphere and reduces the amount of harmful ultraviolet radiation that reaches Earth from the sun. The ozone layer is like the Earth’s personal sun protectant, it’s role is to absorb the harmful UV rays that are sent from the sun.
The third surprising reason is due to the cleaner air we have in the Southern Hemisphere. These three factors mean that it is essential we protect our skin from those harmful rays even on cloudy days.