Powerful solar storms are an imperfectly understood threat to the world's power grids, but one with the potential for economic damage so catastrophic that the estimated $100-200 million it would cost annually to deploy an operational space-weather warning system could be trivial by comparison.

In a “perfect storm” scenario, when a high-power coronal mass ejection (CME) of charged particles slams into Earth at a time when the delicate balance operators try to maintain in electric power grids is precarious, the resulting damage could take a decade to repair at a cost very roughly estimated by the National Academies of Science as high as $1 trillion.

In recent congressional testimony and a public forum in Washington, space-weather experts caution that the 1859 solar storm observed by British astronomer Richard Carrington is only the most powerful one detected so far. That storm took down parts of the growing U.S. telegraph network, starting fires in the process and subjecting some telegraph operators to electric shock.

Recent calculations suggest there is a 6-12% chance of another storm at that level in any given year. But since there were no networks of long electric wires crisscrossing the planet before the 19th century, there is really no way to know precisely how bad “the Carrington event” really was, according to Tom Mahony, senior advanced systems manager at Ball Aerospace.

“We've only had 150 years to observe these events,” he says. “We're projecting this as a 100-year event when we've only observed it for 150 years. We have geological records that go back millennia.”

Solar storms, and particularly CMEs, can pose a health threat to astronauts in space and passengers on airliners passing over the poles, where protection from Earth's magnetic field is weakest. They also can damage spacecraft electronics, and increase drag on satellites so they consume more fuel to maintain their proper orbits. But the most serious potential for damage rests with the transformers that maintain the proper voltage for efficient transmission of electricity through the grid.

On Dec. 4, Mahony told a panel sponsored by the Space Enterprise Council and the George C. Marshall Institute that by National Academies' calculations, there are 2,000 ground transformers and 140 million more mounted on power poles that are vulnerable to CMEs. Under the right conditions, it is at least possible that a major CME could cause so much damage that power would be off or compromised indefinitely. Listing the resulting impacts on food and water distribution, health care and the economy, Mahony warned the results could be dire.

“We are so dependent on electronic transactions for everything—buying groceries, buying gas—that you can easily see how this could decay into serious civil discord,” he says. “We can't really avoid the event. We can mitigate the impacts, and that means we need to know what's coming.”

With warning, says Catholic University of America economist Kevin Forbes, power-grid operators can take precautions to protect their systems, including making sure they have enough “reactive power” available to expend on keeping the networks balanced during a storm, and perhaps “ease up on their transmissions so as to produce closer to home so they're not vulnerable to those fluctuations in the electricity flows.”

Forbes has calculated the outage costs that electric utilities pass along to their customer base at $5,000-10,000 per megawatt hour. At that rate, paying for an operational warning system is cost effective.

“Would it make economic sense,” he says. “The answer is probably 'yes,' because the economic cost of a blackout—even if the transformers are not permanently damaged—is huge, given that $5,000-10,000 figure that I put forward.”

In a House Science Committee hearing on the same subject, witnesses agreed with the thrust of the latest National Research Council decadal survey on space weather, which was released in August. At the top of the priority list, which was based on a survey of researchers in solar and space physics, was a call to complete the present program of spacecraft designed to expand knowledge of how the Sun's violent nature impacts the space around it.

Collectively the 18 solar-observation spacecraft NASA is flying, and the network of ground facilities run by the National Science Foundation (NSF) comprise a virtual “Heliophysics Systems Observatory” that collects information on the solar flares and CMEs, as well as how the solar wind spreads through the solar system and interacts with Earth's magnetic field.

But the scientific satellites in the virtual observatory have limited lifetimes that will begin to expire by late in the current decade, and so far there is no plan or money to use the knowledge they collect to establish an operational system.

“We have to have complete observations of the Sun, the interplanetary medium, the effects at Earth,” says Daniel N. Baker of the University of Colorado, who chaired the NRC's decadal survey committee. “We have to have the models, the tools that are necessary to tie all this together.”

Just doing that “requires an investment of more resources than are presently available in the budgets of any of the agencies,” Baker testified. “And so the vision we laid out was one which would require another $100-200 million per year over this next decade, without doing damage to the basic science or the ongoing activities of [the National Oceanic and Atmospheric Administration] or NSF or any of the other agencies.”

Baker's panel called for a follow-on study to address the issue of funding and division of labor between NOAA and NASA. Near-term, he says, NASA could take on more of the operational role carried by NOAA's National Weather Service if funds for a dedicated operational system are not forthcoming.

That is likely, committee members warned, given the current budget crunch across the U.S. government. The decadal survey report included “decision rules” for policymakers to follow as they try to wedge the appetite for expensive space and ground hardware into the dwindling budgets for the relevant agencies. While NOAA and NASA take the lion's share of responsibility for solar-weather science and forecasting, a senior Democrat on the Republican-led panel suggested the Pentagon could play—and fund—a bigger role.

“One thing that we didn't have a chance to get on the record was not just the impact to us as civilians, and the impact in this environment, but what the impacts are on our critical infrastructure that is related to national security,” says Rep. Donna Edwards (D-Md.).

Given the predictions of what could happen to civil society if the grid goes down, and the high cost of repairing it if it does, a military contribution to fielding a constellation of satellites able to monitor the Sun—and issue warnings as soon as possible based on models derived from the ongoing scientific research funded by NASA and the NSF—would neither be unreasonable nor particularly burdensome.

“At $5,000 to $10,000 of damage for every megawatt hour that doesn't get delivered, you don't have to prevent that many blackouts to recoup that $100 million,” says Forbes.