This is ten times faster that anyone had predicted, says New Scientist magazine, which reported the temperature drop. He thinks it is the biggest and most unequivocal sign that the world's climate really is changing. Below the mesosphere is the stratosphere, which begins nine miles up. Cooling here has been greater than predicted for the last five years. The forecast is that in 20 years the greenhouse effect will have made even the lower stratosphere eight degrees lower.
Ozone is affected because pollutants such as CFCs destroy it far faster at low temperatures.
The Antarctic ozone hole swells during the winter for this reason. Decreases in ozone mean that more harmful ultraviolet radiation reaches the Earth's surface. The scientists' study coincided with the announcement in the UK of a new scale of the strength of the sun's rays. The scale, from one to 20, will be used in weather forecasts to allow people to take appropriate protective measures, depending on their natural skin colour. The UK will score one in winter and around eight in summer.