The freezing temperatures and heavy snows of this winter may have their origins in the fact that the world's volcanoes erupted last year with three times the frequency that they did in 1976.
The two biggest eruptions, one last March on the Kamchatka Peninsula in the Soviet Union and the other last August in Usu, Japan, sent dust and ash so high that the debris is still circling the world in the upper atmosphere.In all there were 28 new volcanic eruptions in 1977 and at least seven others that began in 1976 and continued through a good part of 1977.
"It's been an idea since the time of Benjamin Franklin that volcanic eruptions precede cold and wet weather," said Dartmouth College's Dr. Robert Decker, who is on sabbatical leave at the University of Hawaii studying the phenomenon. "There seems little question that when the fine dust from big eruptions gets into the global stratosphere it can form an opaque layer to keep some of the sunshine out."
Franklin was American ambassador to France at the end of the Revolutionary War when an enormous eruption in Iceland sent a volcanic fog over North America and Europe. It was followed by two of the coldest winters in the memories of inhabitants at the time. Franklin wrote a paper in 1783 in which he theorized that the volcanic haze kept enough sunlight out to make temperatures colder.
Almost two centuries later, Dartmouth's Decker has set out to prove whether or not Franklin was right. Decker is being joined in the attempt by a growing number of climatologists, including Drs. James Kennett of the University of Rhode Island, Reid Bryson of the University of Wisconsin and Stephen H. Schneider of the National Center for Atmospheric Research in Boulder, Colo.
"Volcanoes cause cooling, we're pretty sure of it now," Schneider said in an interview during the annual meeting of the American association for the Advancement of Science being held here this week. "And a cool planet makes the jet stream move faster and expands it southward, which at least helps to explain the cold temperatures and heavy snows and rains we've been getting this winter."
Not only this winter, perhaps, but last winter as well: Schneider says that an explosive volcanic eruption in Guatemala in 1975 may have circulated enough dust in the upper atmosphre to have played at least a part in last year's frigid 1976-77 winter.
"It takes as long as a year, and in some cases two to three years, for volcanic dust to circulate around the entire globe." Schneider said, "so it's not out ot the question that the 1975 eruption may have played a hand in the 1976-77 winter."
History shows a strong link of volcanic eruptions and cold climates. The eruption of Mount Agung on the South Pacific Island of Bali in 1963 was followed by two cold winters, the second colder than the first.
Schneider shows that massive eruptions in 1912, 1903 and 1895 were all followed by colder-than-normal winters. The infamous blizzard of 1888 took place in the same year in which therw were several explosive volcanic eruptions.
Going back into more ancient times, Rhode Island's Kennett has found what he belives is solid evidence correlating volcanic activity and the onset of prehistoric ice ages. Digging up deep-sea sediments from the Pacific Ocean that go back 22 million years, Kennett thinks the ice ages that formed the Antarctice ice caps fit in nicely with what must have beem one of history's most volcanic periods.
None of these scientists is sure what mechanism in volcanic eruptions triggers cold weather. They believe it is the ash and dust that reaches stratospheric heights and keeps the sunlight out, but they're not certain. Dartmouth's Decker thinks erupting volcanoes send tiny droplets of sulfuric acid into the stratosphere that persist there for so long they eventually serve to cool the surface of most of the earth.