The Ozone Hole
Chris - In 1985, you discovered the hole in the ozone. How did you make that discovery?
Brian - We had been measuring the ozone since 1957, so we had already established the climatology of the ozone - what the ozone does season-by-season, day by day. We got used to what it looked like, so when we saw the pattern changing in the late 1970's, early 1980's, we knew something was happening.
Catherine - What does the ozone layer do on this planet normally?
Brian - It absorbs ultraviolet light (UV) from the sun. UV is dangerous for most living things. It can damage cells, so it can damage skin and crops. We can actually monitor the ozone layer by looking at this UV light. Because the ozone absorbs it, all we have to do is look at the UV coming down from the sun. If there is a lot getting through, there can't be much ozone.
Catherine - What area of the world has problems with its ozone layer?
Brian - Every area of the world has problems. Because we saw it in Antarctic and politicians took some action about it, ozone depletion over most of the world is relatively mild. It's a real problem in the Polar regions and particularly in Antarctica. We got a lucky break. Antarctica is the last place we expected to see the results of man-made pollution when there aren't too many people living there. But if the hole was over more populated areas, we would be in trouble.
Chris - Why is it in Antarctic?
Brian - During long winter months in the Antarctic, you get several months of complete darkness. Because it's dark, the atmosphere radiates infrared radiation into space, and it gets cool -the stratosphere gets below -80C! At that temperature, you get rare clouds forming that you don't get anywhere else. The CFCs -the chemicals from man-made products that started the hole in the ozone -deposit double chlorine particles (Cl2) on these clouds. When the sun comes out in spring, it splits these doublets into separate chlorine molecules, which destroys the ozone
Catherine - Why isn't ozone depletion compensated for by other parts of the ozone layer?
Brian - Darkness in winter causes very cold temperatures. This causes a stratospheric vortex of air, which keeps to itself and excludes other parts of the stratosphere. There isn't a chance to get ozone from elsewhere until the vortex breaks down when the sun comes back. The ozone each year heals in the spring, but it never gets back completely.
Chris - Why isn't there a hole in the North Pole?
Brian - Everything that happens in the South Pole should happen in the North Pole, but the vortex is different. In the South Pole you have one big circular continent with the ocean going around it. In the North Pole, you have the continents and oceans next to each other. Because land and sea heat at different rates, the temperatures are more confused. Instead of getting a circular vortex like in the South Pole, you tend to get different shapes and sizes. You start a hole forming but then it gets blown off to the side.
Chris - Have the measures we introduced such as knocking out CFCs made a difference?
Brian - Yes. We have eliminated tough CFCs, and we are adding more chemicals to the list. The amount of those chemicals in the atmosphere is now turning over. The ozone hole that got worse during the1980s has now bottomed out. But we don't expect to see the ozone getting to where it was before until 2070