Floods, mud slides, and generally one of the wettest springs on record for North America and parts of Europe - certainly the weather has been extreme. But is it, as some experts suggest, ''volcano weather''?
No one can answer that question with certainty. But if volcanic eruptions, such as the dirty outburst of El Chichon in Yucatan last year, are the culprits, their guilt has yet to be established.
El Chichon's major eruption on April 4, 1982, threw much dust and sulfur into the stratosphere. Its dust veil is some 20 times larger than that of Mt. St. Helens. The stratospheric debris now contains large amounts of sulfuric acid. It is typical of the volcanic fallout that might well influence weather by blocking some incoming sunshine.
Brian Toon of the NASA Ames Research Center has suggested, on the basis of computer simulations, that El Chichon's cloud could cause an average cooling of 0.5 degree C., with the cooling effect becoming evident in 1983 and peaking in 1984. His forecast has been cited widely since it was made last year. This spring's weather in parts of the Northern Hemisphere might seem to bear it out. The pattern is reminiscent of the cooling that followed the eruption of Krakatoa a century ago or of Agung in Bali in 1963.
However, Mick Kelley and Chris Sear of the Climatic Research Unit at Britain's University of East Anglia have recently challenged such a notion. They studied several significant Northern Hemisphere eruptions and the ensuing weather to reach a startling conclusion: If the El Chichon cloud has influenced weather, that influence should now be over, not building to a climax.
It should indeed take a year or more for Northern Hemisphere weather effects to appear after a Southern Hemisphere eruption, they say. But, if history is any precedent, Northern Hemisphere eruptions have their maximum effect immediately - that is, within a couple of months. A rapid fall in average temperature is followed by a slow recovery over the next two years.
Kelley and Sear say El Chichon might be blamed for a roughly 0.5 degree cooling observed in average hemisphere temperature a year ago. But, as explained in a report of their work in New Scientist, they expect the climate to be recovering from that cooling now.
This prediction runs counter to forecasts, such as that of Toon, which indicate volcano-induced cooling will be most intense later this year or early next year. In essence, meteorologists now have a natural experiment with which to test these different views of volcanic influence. If the cooling the computer models have indicated doesn't show up - that is, if Kelley and Sear are right - it may be time to revamp the models.
Meanwhile, geophysicists at Columbia University's Lamont-Doherty Geological Observatory have looked for volcanic weather effects in tree ring data going back to 1690. Edward R. Cook says that this record indicates that volcanoes are influencing recent climate.
He explains that North American weather tended to be relatively benign during the period from about 1900 to around 1960. There were fewer weather extremes than at other times, he says. He then notes that this 60-year period was also relatively free of volcanic eruptions. The frequency of eruptions, and of weather extremes, seems to have picked up in recent decades.
All told, according to a Columbia announcement, it appears that North America , at least, has re-entered a period of frequent extremes of weather. The past few years, which have swung from damaging drought to inundation, might seem to exemplify this. And volcanoes seem to be implicated, as well.
Yet, here again, no cause-effect link has been proved. Veteran climatologist Helmut Landsberg of the University of Maryland, for example, has long warned against concluding that climate is changing or becoming more variable on the basis of what has happened in recent decades. He reiterated this warning in one of 20 studies in the Global 2000 Revised project, which was presented at the meeting of the American Association for the Advancement of Science in Detroit last month. There is, he says, no solid basis to conclude that climate is worsening to any significant extent.
Thus, while most meteorologists would concede that volcanic-dust veils might well affect weather, the nature of this effect still is poorly understood. As for this spring's extreme weather, the role of El Chichon, if any, remains obscure. Cosmic powerhouse
The most luminous object in the universe may also contain the most massive cosmic body. It's a body with the mass of 10 billion suns.
Wayne Stein of the University of Minnesota, in a talk prepared for a meeting of the American Astronomical Society in St. Paul, explains that the body lies at the heart of an object known only by its astronomical-catalog number: B2 1308+ 326.
This is one of the most powerful energy sources known. In seven years of observations, a number of astronomers have seen it produce massive outbursts of light at roughly yearly intervals. At the peak of the latest outburst early this year, the object became the brightest light source in the universe.
Stein explains that the nature of the energy supply for such an object is a major astronomical mystery. But his studies of the outbursts indicate that, whatever the source is, it is extremely massive. He called his assessment of a mass equivalent to 10 billion suns ''one of the first pieces of direct evidence that bears on the nature of the central energy generator. . . .''
However, he added: ''. . . we don't know exactly how to interpret these outbursts. The central source could be a rotating supermassive object or a pulsating object. Whether or not this supermassive object should be interpreted as a black hole is a matter of personal taste.'' A black hole is an object that has collapsed to the point that its gravity is too intense for anything to escape, even light.