Have you lost the plot?; A three-part series that explains the issues behind the news

Blowing hot and cold: is our climate becoming more extreme?

Last year moved from one extreme to the other, with a stiflingly hot summer and a bone-chilling spell in December. So what of the so-called "greenhouse effect" that became imprinted on the public consciousness in the late Eighties?

The summer weather seemed to back up scientists' warnings of a man-made climate change, which would lead to the melting of glaciers and a rise in world sea levels anticipated in the film Waterworld, aptly released at the height of the heatwave. But then, late in the year, temperatures dropped to -20C in parts of Scotland, and summer became a distant memory. Yet even as the nation shivered, climate experts claimed that the world as a whole was experiencing the last days of the hottest year since reliable record-keeping began.

The year's dramatic vacillations in temperature in Britain did not shake the growing scientific consensus, expressed at a conference in Madrid in November, that global warming is under way, and that the Earth's climate has indeed been affected by humanity's activities. A report published by the Countryside Commission claimed that droughts such as last summer's and that of 1976 - thought to be one-in-357-year freaks - could happen every 14 years. Furthermore, according to Professor Keith Clayton, author of the report,"as global temperatures rise, temperatures in the Mediterranean will be so high in summer that many people will find them unpleasant".

There are still a few dissenters. But most experts believe we can do some things now that are desirable in their own right, such as improving energy conservation in British homes and using less private transport. These will bring social gains in any case and will help to minimise the damage if the worst fears start to come true.