Scientists looking for explanations for the freakish abnormality of thisyear's rainfall are unlikely to spend much time examining El Niño, writes Brendan McWilliams
They seek him here, they seek him there; El Niño, they say, must be behind it all.
This most elusive eminence grise is being blamed for the Black Sea floods, the excessive rains in India, the overflowing rivers of Europe, and for the droughts in parts of Australia and in Vietnam. It has even been hinted that El Niño may bear some responsibility for our own rather miserable summer. But why has this quaintly named scapegoat so suddenly been resurrected?
El Niño, as many of us will remember from its last appearance in 1997/98, is a general warming of the surface waters of large areas of the Pacific Ocean near the equator which occurs at irregular intervals of between two and seven years.
This anomalous warmth injects a great deal of extra energy into the atmosphere, and plays havoc with the normal climate of the lower latitudes.
At the peak of an El Niño the normally arid areas of western South America are drenched with rain; Indonesia and the Philippines experience droughts at times when abundant rain might be expected; abnormally dry weather facilitates wildfire epidemics in Australia; and enhanced hurricane activity off the western coast of Mexico often brings storms and floods to southern California.
The last El Niño episode, about five years ago, was exceptionally strong. Sea surface temperatures in parts of the Pacific rose to five degrees or more above their normal values, and regional climates were thrown into considerable disarray.
Now, after the customary lull, it has been observed during the last few months that sea temperatures in the tropical Pacific have again climbed to a degree or two above the average, so there is a growing consensus that another El Niño has arrived.
But there is also a general consensus among climate forecasters that this event, expected to last until early 2003, will be significantly weaker than that of 1997/98, and that its climatic consequences will be correspondingly less catastrophic.
Nonetheless, despite its weakness, it is not unreasonable in the current circumstances to look to the emerging El Niño to explain unusual weather events in the subtropical arena. It may well be that the current droughts in parts of north Australia and in Vietnam, and the recent heavy rains in Ecuador, Peru and Chile may be related to it. Moreover, since the phenomenon is also known to affect the climate of parts of the US, the current droughts being experienced there may well be found to have some connection with El Niño.
Elsewhere, however, the evidence against El Niño is more tenuous. Severe flooding in India, sadly, is a relatively commonplace side-effect of the summer monsoon rains; these tend to be erratic anyway, affecting different places with more or less severity each year. Insofar as there may be anything unusual about the pattern of the current season, most scientists will be more inclined to look for explanation to the large pall of dust and smoke from wildfires that currently hangs over much of southern Asia.
In the case of the Russian and European floods, thundery rain, enhanced by the sultry continental heat, is a common summer hazard in these parts. The immediate cause of the recent flooding is a deceptively shallow area of low pressure stagnating over the region for quite some time. Low pressure areas like this generate thunderstorms. The question is: what has caused this? Scientists looking for explanations for the freakish abnormality of this year's rainfall are unlikely to spend much time looking at El Niño; experience suggests that its effect on Europe is relatively small, and even then, is limited to enhancing winter rainfall.
Meteorologists will be uncomfortably aware that the average temperature of our planet has risen significantly over the past two decades, and that preliminary figures for 2002 suggest this trend will continue. They will recall that extra heat, in general, is conducive to more and heavier rain, and they will wonder if these freakish falls in Europe will be shown to be related to this global warming.
And the same goes for our own excess of rain in recent months. El Niño has yet to be shown to have a measurable effect on Irish weather. Moreover, we have had wet years in the past, and 2002 may be one just a little worse than usual.
But it is hard to avoid the conclusion that it seems exceptional, and when the books are closed the figures will be examined closely to see if the frequent deluges are in any way related - not to El Niño, but to the inexorable increase in global temperatures.