The Risk of Geomagnetic Storms to the Grid: A Preliminary Review

Abstract

Life on earth evolved to exploit the flow of energy from the sun — and to withstand its extremes. But if life writ large has adapted to its home star, perhaps civilization has not. Some worry that a cataclysm on the sun could trigger a “geomagnetic storm” on Earth that would knock out so many satellites and high-voltage transformers that advanced societies would lose electricity for months or years while waiting for replacements, creating a humanitarian disaster. This paper critically reviews the evidence while explaining many of the technical ideas. It concludes that some researchers have overestimated the risk, at least as manifested in their data, and perhaps as a result have received disproportionate public attention. Most measures suggest that what appears to have been the largest storm since the industrial revolution, the 1859 Carrington event, was less than two times as strong as recent storms, which civilization has shrugged off. I estimate the probability of catastrophe is well under 1%/decade. Yet the evidence on the probability of extreme events is thin, almost by definition, so the risk cannot be dismissed; and it has historically received little attention. We should not be complacent about the threat.