The cold weather east of the Rockies and the drought to the west may have been triggered at least in part by a prolonged lack of activity on the surface of the sun.
"It's hard for me to believe that the sun cares about what the weather is like in Boston and Buffalo," Dr. John A. Eddy of the Harvard University-Smithsonian Observatory Center for Astro Physics said in an interview here today. "But the fact is we should have been into a rise of solar activity in the autumn of 1975 and here we are a year and a half overdue into getting that rise."
Eddy told the annual meeting of the American Association for the Advancement of Science that he did not believe the sun was the main culprit in this winter's weather, but that he did believe it could be counted among the suspects to blame for the western drought and the eastern ice.
The sun reached the high point of its 11-year sunspot cycle in 1969; then began a decline in sunspots that should have reached a minimum in the fall of 1975. The period of minimum activity extended for a year and a half, only beginning in the last month to show signs of reversing itself.
Sunspots are believed to be disturbances in the sun's magnetic field caused by sudden surges in temperature and a speeding up of the sun's rotation. Scientists long have believed sunspots may disrupt radio communications on earth. Now, scientists suggest sunspots might influence the weather as well.
"Whenever the sun loses its spots over a long period of time, the earth has gone into a very cold spell," Eddy said. "When sunspot activity is as low as it's been the last two years there is a change in the solar wind that could result in a change of the circulation patterns of the earth's upper air.
"I don't know why but we don't understand it," Eddy went on, "but I guess it's like asking the fish at the bottom of the sea to know if it's raining on the top."
Scientists still believe the main culprits in any changes in the weather are the dust, pollution, carbon dioxide and sulfur dioxide that climb into the upper atmosphere from the surface of the earth, causing temperature and wind changes.
Dust has been blown all over the globe the last two years by winds carrying sand out of the Sahara desert. Aerosols -- small particles -- from industrial pollution are at a record high and more and more carbon and sulfur dioxide is reaching the upper atmosphere as more and more coal, oil and natural gas are being burned by the industrial civilizations of the earth.
"This is why you get worldwide weather shifts -- the amounts of dust and pollution that can cut off the sun's light and heat from certain parts of the earth," Eddy said. "It's as though someone is sitting up there in the upper atmosphere pulling the slats on a venetian blind."
In spite of all the earth's surface activity, Eddy said there is growing evidence that the sunspot cycle can at least be tied to the drought that has now plagued 11 Western states for the last year.He said that work done by scientists at the University of Arizona on tree rings suggests that drought strikes the West every 22 years, at the end of every other 11-year sunspot cycle.
Sunspots regulate the solar wind, which itself regulates the number of charged particles reaching the earth's atmosphere from the sun and from cosmic rays. If sunspot activity is down, the number of charged particles reaching the earth goes up.
One of these charged particles is radioactive carbon-14, which is sucked into the lower atmosphere and into the earth's trees. Records of its presence are locked up in the growth of these trees. A measurement of carbon-14 in tree rings is a measurement of solar activity going back through the hundreds of years it takes the biggest trees to reach full growth.
University of Arizona scientists led by Dr. Charled W. Stockton have measured radioactive carbon in the trees at 40 or 50 sites scattered throughout the West. They have found that carbon levels were high 22 years ago, 44 years ago and 66 years ago.
"That ties into the great droughts in the plains states in the 1950s, in the dust bowls of the '30s and in the great drought of 1910," Eddy said.
Stockton said their tree ring studies went all the way back to the year 1700, with almost all of the studies correlating 22-year drought cycles with falloffs in sunspot activity. He said they studied drought-sensitive trees like oak, pine and douglas fir.
It is more difficult to tie solar activity with the bitter cold and snowfalls suffered by states east of the Rockies this year, but the same upper air masses that are carrying precipitation away from the West are dumping it on the East.
"The West is experiencing drought," Dr. Eddy said, "and the East its now usual amount of snow plus whatever snow the West would have had in a normal year."
The same Arctic winds that carried snow out of Alaska and east of the Rockies have also produced cirrus clouds that served to block out long periods of sunlight. Scientists say this has contributed to the coldest winter in 100 years east of the Rockies.
Difficult as it is to link brief lapses in sunspot activity to this year's cold winter, Eddy said long periods of low solar activity in the past can be correlated to long periods of cold temperatures on earth. Again, the study of tree rings around the globe have shown a direct tie between the two, he says.
The period matching the reign of France's King Louis XIV from 1643 to 1715 was a period of high radioactive carbon-14 levels in the earth's tree rings. Eddy, who also checked historical records, said the most severe temperature drops on the earth in the last 1,000 years occurred during that period.
Crops failed throughout the British Isles, the Norse colony in southwest Greenland perished from the cold and the Spanish Conquistadors wrote that they rode their horses into Mexico across a frozen Rio Grande.
Scandinavians reported that there were no displays during that period of the aurora borealis, which is produced by showers of solar particles striking the earth's magnetic fields. British astronomer Edmund Halley was 60 years old when he saw his first northern lights in 1715, the year the "little ice age ended."
Eddy said it is impossible to say if next year's winter will be a repeat of this year's, because there are too many variations in the earth's climate. And there are signs now that the sun is about to resume an upward climb in its sunspot cycle.
Scientists at Arizona's Kitt Peak National Observatory have noticed a growing number of sunspots in the more northerly regions of the sun between 40 and 50 degrees latitude. Normal upward sunspot cycles begin in the northerly latitudes, then migrate south toward the solar equator.