06/01/93
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STANFORD -- There are 2,000 thunder and lightning storms cracking the skies somewhere in the world at any moment. A growing number of scientists believes that those electrical outbursts are having a much greater influence on climate and the weather than anyone thought.
The latest evidence that this is so - and that predicting such things as global warming and climate change are far more complex than many think - comes from a serendipitous experiment by a Stanford engineer, one that has nothing to do with electrical storms or weather.
Antony Fraser-Smith, professor of electrical engineering and geophysics (research), seems to specialize in serendipity. An expert on the earth's magnetic field, one of his experiments detected a burst of electromagnetic radiation just before the 1989 Loma Prieta earthquake. That has led geophysicists to speculate that he may have found a reliable warning system for some quakes and he now has experimental devices planted on the ground in several parts of California to test this theory.
It was, in turn, one of those experiments that came up with the lightning hypothesis.
Fraser-Smith had placed one of his detection devices in Corralitos, a small town in southern Santa Cruz county in what geophysicists called a "seismic gap," an area in which there are not many seismic detectors and there is fear of a major earthquake.
On Sept. 23, 1990, a thunderstorm, fairly rare in that part of California, roared into Corralitos, knocking out power. Fraser-Smith's detector, unlike most instruments used in experiments of this kind, was equipped with a battery-operated backup system and kept going.
Normally what happens with such experiments is that researchers ignore the electrical storm, considering it nothing more than an interruption in the data stream.
"I don't know what made me look at the data," he said, "because I hadn't had much of an interest in making measurements up close to thunderstorms. But very clearly, when we got the data back, there was a big burst of activity during the storm. I sort of expected that...but this time around, I thought that was very interesting."
The magnetic field fluctuations between one-hundredth of a hertz to 10 hertz jumped to between 20 and 50 times normal during the storm.
He compared that to a device on the Stanford campus (which measures from 10 Hz to 32 kHz) that showed fluctuations two to three times normal during the storm in the frequency range where scientists know lightning has an effect.
"If there is this big increase from a single thunderstorm, all the thunderstorms in the world are probably feeding a great deal of energy into this frequency range into the earth's environment," Fraser-Smith said.
Fraser-Smith and an undergraduate student, Laurie Bloomgarden, obtained lightning strike data for that storm from the California Department of Forestry (CDF) office in Felton and looked at the data from the detectors when CDF recorded lightning.
Until now, Fraser-Smith said, scientists believed lightning had only a peripheral role to play in frequencies below 10 Hz Most of the signals and noises recorded above that range were thought to be the result of the solar wind interacting with the magnetic field.
Fraser-Smith found that the fluctuations at the lower frequencies exactly matched the fluctuations of the lightning in the storm.
"The magnetic field from a thunderstorm varies exactly like the normal natural background noise that we record at any time where there are no thunderstorms near us," he said.
Fraser-Smith's hypothesis is that lightning plays a much greater role than believed in electromagnetic fluctuations in the earth's environment, which affect such things as climate, and are far more complex than first thought.
"My attitude has now changed," he said. "Thunderstorms may be a major source, perhaps even the predominant source of all the radio noise we have on the earth's surface in the range of 10 hertz down to one- hundredth of a hertz."
If the theory is valid, it has the potential for helping scientists subtract signals coming from the upper atmosphere and thunderstorms from the overall measured noise and leave them much more sensitive to signals coming from out of the earth, which has some potential for warning of imminent quakes and of learning more about what is happening inside the earth. "We have no way of interpreting our signals to tell what is coming out of the earth or what is coming down from above," Fraser-Smith said.
"We have at the present time no knowledge that will help us distinguish between them. There might be a substantial amount coming from the earth, and we have not known this."
It could add another variable - this one not even suspected - into climate change.
"All this lightning work is a new factor coming up. How can you predict climate changes accurately if you don't even know some of the variables coming to it?" he said.
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