Monday, 6 July 2009


People in Europe and the USA seem oblivious of what we in Australia call the hole in the ozone layer. So I thought a little education was needed, since they helped cause it to appear! This hole lets in UV rays that humans have not evolved to be able to take in large doses. Primarily it affects our skin, and that of other animals too and is the single greatest cause for our enormous rate of skin cancer in Australia. (Personally I think that chemical sunscreen is the main cause but what would I know??) Although the hole is not directly over Australia, as the earth turns during the day, the sun shines through the hole onto all southern countries. We have all also noticed that fruits are much more often ruined now by sun burn than ever when I was child. Tomatoes and capsicums are particularly easily damaged and everyone here in South Australia is erecting light shade over their summer vegetable gardens these days.

The following is an excerpt from the online Eco News, an excellent, free newsletter you can subscribe to, as I do.

In the early 1980s, through a combination of ground-based and satellite measurements, scientists began to realize that Earth’s natural sunscreen was thinning dramatically over the South Pole each spring. This large, thin spot in the ozone layer caused by chloroflourocarbons (CFCs) came to be known as the ozone hole.

ozone hole 1979-2008 In 1979, the ozone hole reached its maximum depth on September 30. At 194 Dobson Units (DU), it was not far below the historical low. The hole was confined to a relatively small area centered on the Antarctic Peninsula and the Weddell Sea to its east.

Almost three decades later, the ozone concentration during the 2008 Southern Hemisphere spring bottomed out on October 4, 2008, at just 100 DU. The ozone hole encompassed virtually all of Antarctica and reached across the Southern Ocean toward the tip of South America.

The global recognition of CFCs’ destructive potential led to the 1989 Montreal Protocol banning the production of ozone-depleting chemicals. Scientists estimate that about 80 percent of the chlorine (and bromine, which has a similar ozone-depleting effect) in the stratosphere over Antarctica today is from human, not natural, sources.

Models suggest that the concentration of chlorine and other ozone-depleting substances in the stratosphere will not return to pre-1980 levels until the middle decades of this century. These same models predict that the Antarctic ozone layer will recover around 2040. On the other hand, because of the impact of greenhouse gas warming, the ozone layer over the tropics and mid-southern latitudes may not recover for more than a century, and perhaps not ever.

1 comment:

Alex Flint said...

A much needed exposition! I have also been suprised at how little people in the northern hemisphere are aware of this. However, the ozone layer IS on the recovery and CFCs have been mostly removed from production, so in this sense our reaction to the ozone problem has been one which might inspire optimism in our ability to tackle other, even bigger problems. Climate change also requires fast, worldwide, coordinated action. Can we also turn that problem around over the next decade? Perhaps our children will debate how long the climate will take to recover, rather than how long until it collapses.