Mother Nature was in a funny mood in 1997. In apparent contrast to her normal dull catalogue of common things, she offered us a continuing menu of meteorological surprises, both here in Ireland and around the world. Something very strange, some might say, is happening to the world's weather.

It may seem hard to remember now, for instance, that last March and April the spectre of drought was seen to stalk the Irish countryside. Following one of the driest winters on record, and a brief respite in February, there was no rain worth talking about for six weeks or more; farmers' hopes and the levels of our reservoirs sank together to their lowest for years.

But then do you remember how the balance was redressed? June was wet, there were flash floods in Mayo in July, and in the first week in August the entire southern half of the country seemed to disappear under several feet of water. Then, after the warmest autumn on record, nature threw a Christmas tantrum that gave us our most spectacular storms for more than 20 years.

Some would see a pattern in these occurrences; a tendency for more extreme events to happen much more often than they did before. They argue that this is confirmed by happenings on the global scale. The devastating floods in eastern Europe in July were almost harbingers, in retrospect, of those that came to us in August.

The troublesome El Nino, too, returned to haunt us years ahead of schedule, and became a household word as it was blamed for everything from showers in Schull to typhoons in Portuguese Macao.

Indeed the troublesome infant almost confessed to causing the prolonged torrential downpours that marked the handing over of Hong Kong to China, the weeks of smog in Indonesia, widespread bushfires in Australia, and the anomalous hurricanes on the Pacific coast of California.

And then we remember that 1997 was also the year of the Kyoto conference. Could these apparently extreme events be a sign that our climate, even now, has started changing? Are these storms and floods a direct result of global warming, and is there worse in store for us when the process, finally, becomes established?

The truth is that no one really knows. Theories about climate change can be conveniently divided into three broad categories.

There are the facts, or at least those findings we believe to be the facts; there are suspicions about what may be happening, but for which any evidence is purely circumstantial; and there are the Armageddon theories, bizarre, unthinkable scenarios which, while not impossible, have little real support in mainstream meteorology.

We know, for example, that the average temperature of the world has increased by about half a degree Celsius since 1860, and that the rate of warming has increased significantly in recent years. We also know that the periodic El Nino episodes have certain predictable effects on the climate of the lower latitudes.

What is feared, however, by a growing body of scientists is that some, at least, of the unusually severe weather events of recent years may have been triggered by the observed increase in global temperature.

The evidence is purely circumstantial, and for every such event a previous occurrence of similar severity can be identified.

The storms we had over Christmas, for example, may have been the worst for more than 20 years; but this in itself means that the same thing happened 20 years or so ago, long before the greenhouse effect became an issue. The floods in August were the worst since Hurricane Charlie in 1986, but this, too, implies a precedent in recent decades. So it goes with each and every spectacular event that comes along, and one is also conscious that, simply because of the ongoing debate about global warming , weather is "news" in a way that it has never been before, and any unusual happening makes the headlines.

And yet, more and more scientists are saying, the surprises have been happening much too frequently of late. The computer models tell us that in a greenhouse world the frequency and intensity of extreme weather events like storms and hurricanes may change.

Nobody knows quite how, but there is a suspicion that this may be precisely what is happening now, and that, yes, it may well be because of global warming. The facts are not coercive - they do not necessarily imply a changing state, but they do not contradict it either.

Finally, of course, there are doomsday theories. These are the ones that headline writers love; those that predict an interruption or diversion of the Gulf Stream, bringing Baltic winters to the coasts of western Europe, or those that would have a melting polar ice shelf inundate us all as the levels of the oceans rise inexorably.

Such wild scenarios are long shots, generally regarded as unlikely, and promoted seriously only by a small minority, but in general scientifically sound to the extent that they may not be impossible.