10 MARCH 1990, Page 8


Storms in the greenhouse

IT APPEARS to be our current mode to ascribe the recent violent storms to the greenhouse effect. However, the Climatic Research Unit at the Universi- ty of East Anglia shows that it cannot be proven to be the cause while warning us, nevertheless, that we are likely to have an increasing number of intense storms as the warming-up of the atmos- phere proceeds. Their generation de- pends on convection: masses of warm air coming from the tropical regions move north and are lifted by masses of cold air coming from the poles convection currents are set up. In the colder regions of the higher atmos- pheres the water vapour in the warm air condenses into clouds and rain, giving out its latent heat (the heat which vapourised it in the first place). This heat then increases the strength of the convection current, which is whirled by the earth's rotation into a vortex, in our region known as an Atlantic depression. The greater the difference in tempera- ture between the warm and cold air masses, the more intense will be the depression.

With the warming-up of the atmos- phere, then, the depressions will be- come more intense, and will only de- crease as the polar air becomes less cold — which it may well do as the polar ice-cap melts under the greenhouse effect. The Climatic Research Unit takes evidence that the world has warmed up in recent years, and sees a parallel in the increasing violence of our storms and our having experienced the warmest decade since records began to be kept over a 100 years ago. Since the beginning of this century the world as a whole has warmed up by 0.5°C — which happens to equal the rise predicted from calculations based on the green- house effect. Yet there has always been in the world climate a natural fluctua- tion of 0.5°C. Therefore the greenhouse effect cannot be proven to be the source of a 0.5°C rise causing violent storms.

But that's not the end of it. For one thing, unusual temperature differences in the atmosphere arise from its warming-up being far from uniform over the earth's surface. For another, present-day forecasters with their com- puter models believe that during the next 10 years we are in for a, rise of no less than 1°C, due to our indiscriminate- ly letting loose CO2, methane, nitrous oxide, CFCs into the atmosphere. So: increasing temperature differences, in- creasingly violent storms. Moral . .

William Cooper