How bad is ozone depletion?
Very bad, and getting worse every year! The problem is that most of the gases and vapours that cause ozone-depletion take a long time (10 – 15 years) to homogenise throughout the atmosphere, but they can last up to 100 years for CFCs and 300 years for halons (to remove roughly half of them). Fortunately, one substance that was used very massively as a solvent, 1,1,1-trichloroethane, has an Atmospheric Residency Time of only 12 years, so that, as it was banned in most major using countries in 1996, the levels of this compound in the air are already measurably improving. It should be noted that the “ozone hole” is not really a hole but simply an important thinning of the ozone levels over the Antarctic in each southern spring. The cause is quite complex but is simply driven by a weather situation, in conjunction with the man-made chemicals in the stratosphere. On average, it has become worse each year since it was first discovered. 2003 was the worst yet, with 2001 a very close second. I
