By the time COVID-19 started spreading in late 2019, experts had warned for years that a pandemic was the high-probability global threat. Still, many countries seemed caught on the back foot. As someone morbidly interested in the apocalyptic, I couldn’t help but wonder: What else do we think we’re prepared for, but really aren’t?
Plenty of disasters are a case of when, not if. Each has its own flavor—climate change is a whole buffet—but one in particular has similar traits to the pandemic: We know it’s coming, we know it’ll cause disruption on a global scale, and if we aren’t prepared, it could have a high death toll. It wouldn’t kill directly like a disease; instead, it could take out our electrical and communications infrastructure, disabling the health, food, and fuel supply chains that sustain billions of people. To understand why, and how, let’s go back to 1859, to the English astronomer Richard Carrington.
Carrington was part of the first generation of astronomers to study the Sun in detail. Born into a wealthy brewing family, he could afford to drop out of academia and build his own observatory on the grounds of his country manor in Redhill, a rural town halfway between London and England’s South Coast, where he would sit each day watching the surface of the Sun projected onto a cotton sheet via his telescope. At 11:18 a.m. on the morning of September 1, 1859, he saw two brilliant white points of light emerging from a large cluster of sunspots. He quickly sketched what he’d seen, and included the illustration with a report published in the a couple months later. (Richard Hodgson, an amateur astronomer who lived in Essex, offered a less detailed version of events in the same journal.)
By the following evening, the particles from those flares had reached Earth, and the sky was ablaze with auroras—the northern (and southern) lights. In the Rocky Mountains, campers woke and started making breakfast at midnight; a man in New Orleans went hunting at 1 a.m. From North America to East Asia, Hawaii to Colombia, Brisbane to Cape Town, crowds stayed up all night to stare at the razzle-dazzle: “alternating great pillars, rolling cumuli shooting streamers, curdled and wisped and fleecy waves,” reported , “rapidly changing its hue from red to orange, orange to yellow, and yellow to white, and back in the same order to brilliant red [until] lost in the beams of the rising sun.”
The appearance of auroras near the equator might not sound like a disaster, but the lights were just a sideshow. The huge, invisible storm behind the phenomenon is what should worry us today.
Earth is constantly being struck by charged particles blown out by the Sun across the solar system. Solar storms result from coronal mass ejections (CMEs), a release of billions of tons of charged plasma that follows solar flares. Particles travel along Earth’s magnetic field lines, which converge at the poles—and, as they travel through the atmosphere, they excite oxygen and nitrogen atoms so they emit light. The worse the weather in space, the further south or north the particles break in, and the further the auroras travel: The Carrington Event was caused by the biggest known CME of the last 200 years. But the charge in those particles has to go somewhere. The Carrington Event happened during the early years of the telegraph—the first human-made technology vulnerable to such geomagnetic flux—which gives us an inkling of how chaotic a similar solar storm could be in the present.
During the most extreme storms, changes in Earth’s magnetic field induce electrical current in conductors on the planet’s surface—notably, metallic structures like oil pipelines, railway tracks, and electrical transmission lines. In 1859, the global telegraph network had more than 200,000 kilometers of cables, mostly in North America and Europe. As the storm peaked, operators from San Francisco to Bombay found their cables and equipment overwhelmed by the “auroral current.” In New York City, one man was left stunned by an “arc of fire” that shot off a ground wire onto his forehead; an operator in Pittsburgh saw “streams of fire” pouring from his circuits as they nearly melted. Telegraph operators in Boston and Portland, Maine, disconnected their batteries but found the storm current was enough to power the line on its own, while across the world messages were blocked, their signals overwhelmed. Normal service only resumed after several days, as the flux faded and equipment was repaired.
The Carrington Event happened before mass electrification. Today, the world is criss-crossed by billions of kilometers of cables—and if a similar storm were to hit, the disruption could be orders of magnitude worse. Anything that handles high-voltage AC power, like substation transformers where power from the electrical grid is stepped down, is especially vulnerable to overheating, melting, or catching fire.
Transformers are large, expensive objects, often taking months to design, build, and test for specific sites. A 2014 Congressional report found that if more than eight transformers in the United States were destroyed simultaneously, the country’s entire grid system would collapse. Since it can take up to 20 months to build, test, and install new transformers, many areas could see extended periods with reduced grid power, or even none at all. At worst, the damage to the grid could lead to cascading economic and public health failures across large regions, or even continents, as logistics chains—for food, gas, medicines, delivery of replacement parts—struggle to recover. A 2016 FEMA training exercise assumed the worst problems in urban and populated suburban areas would kick off on the eighth day after a hypothetical 1859-scale storm because most facilities that use backup generators, like hospitals, often only keep a week’s worth of fuel on site.
But even if the grid remains intact, solar storms can cause communications blackouts. High geomagnetic flux in space and the atmosphere can overwhelm some of the frequencies used for radio transmission, even interfering with cellular services. Some storms have temporarily or even permanently disabled satellites and significantly degraded GPS accuracy: A relatively minor storm in October 2011 knocked out North America’s flight navigation system for several hours. Anything that relies on satellites and/or radio transmissions could be affected.
The most dangerous place for satellites to be during a storm is in low-Earth orbit, on the edge of the atmosphere where geomagnetic flux is high. Satellites from the likes of NASA are hardened against all but the worst disruptions, but the last few years have seen the rise of programs like SpaceX’s Starlink, with fleets of thousands of relatively cheap, unhardened, and seemingly unreliable micro-satellites offering anyone on Earth high-speed internet “unbounded by ground infrastructure limitations.” Because large solar storms also increase atmospheric drag in low-Earth orbit, one could potentially fry these fleets, knock them into unpredictable orbits, and, once the collisions stopped, leave behind a debris field that would block any replacement launches until it burned up a few years later.
Consider how much more intertwined communications and power have become over the last decade or so. Many industries increasingly rely on networked technologies to improve efficiency—like energy companies, which use real-time data to balance power across their grids—while any facility with its own on-site AC transformer could be vulnerable to power loss. That includes large data centers, making anything in the cloud particularly vulnerable. It also potentially includes the unassuming buildings where multiple undersea cables reach land, according to a 2017 report from the Foundation for Resilient Societies, which looked at examples in the Pacific. As Ryan Wopschall of the International Cable Protection Committee told me over email, “submarine cables get damaged [and replaced] all over the world every year,” and this can slow traffic between two points to a crawl as data is rerouted and a global fleet of repair ships advances to fix the problem. The internet was designed to survive nuclear attacks, with data always able to take an alternative route if it has to—but a global event that takes down multiple cable nodes at once could be enough to cause a temporary balkanization.
I could go on, but this kind of systemic collapse is why a 2008 report by the U.S. National Research Council endorsed a $1 to $2 trillion price tag on a repeat of the Carrington Event. The physical damage is one thing, but the ensuing consequences are mind-bending—that 2008 estimate was just for the first year after the storm, and mainly examined the collapse of the U.S. electrical grid.
Whether this assessment is overly alarmist is a matter of ongoing debate. In researching this piece, the wide variation in predictions and opinion reminded me of how so much pandemic planning rested on the assumption that we’d be facing a new strain of influenza, not a novel coronavirus. For example, if you look up the most recent edition of the UK’s National Risk Register, published in 2017, which reports on various natural and terror threats, you’ll find an influenza pandemic at the top of the list. Other “emerging diseases” are in a lesser category, alongside severe droughts, heat waves, and “space weather.” (Grouping all space weather together is a strange decision, much like grouping Mauna Loa with Mount Saint Helens.) Similarly, various U.S. government bodies have investigated electromagnetic threats since the Cold War, but they’ve tended to focus on the potential military or terror applications of electromagnetic pulses, with geomagnetic storms as a secondary concern.
When the next big storm hits, three ongoing and widespread efforts will likely determine the scale and scope of its impact: research into the size and effects of past storms, active forecasting and monitoring of new storms as they approach Earth, and addressing known infrastructure vulnerabilities, for example by retrofitting grid transformers to fortify them against geomagnetically induced current surges.
While CMEs are incredibly common, sometimes happening multiple times per week, most, fortunately, miss Earth. The most well-studied modern example came in 1989, when a storm overwhelmed and shut down the Hydro-Québec hydroelectric grid in 90 seconds, leaving 6 million people across Quebec without power for nine hours. The largest storm of the 20th century was the May 1921 “Railroad Superstorm,” during which abnormal currents in railroad tracks and telephone wires caused fires across North America and Europe, including one at Grand Central Terminal in New York City. A September 1941 storm blocked radio transmissions in the North Atlantic; German U-boats hunted down isolated Allied convoys lit up by the northern lights. There’s also the “Halloween Storm” of 2003, which caused a short blackout in Sweden and a spate of problems in space—NASA says more than half its missions were disrupted as satellites malfunctioned.
A 2012 study published in the journal put the chances of another Carrington-level storm happening within the next decade at 12 percent, but more recent estimates are lower: between 0.5 to 1.9 percent, according to a 2019 paper in the journal . It’s hard to make strong estimates because storms leave only faint archeological traces—solar particles hitting the upper atmosphere form carbon-14 and nitrates, which get deposited in tree rings and ice cores. There’s tree ring evidence to suggest that bigger-than-1859 storms—possibly 20 times larger—occurred in both 774 CE and 5480 BCE, but such evidence is inconsistent. If the Carrington Event left anything behind, the traces are so faint that it’s impossible to reliably identify them, and the same likely applies to other storms, too. Scattered historical accounts—like Assyrian tablets attesting to “red cover[ing] the sky” 2,700 years ago, a resident of Lisbon describing “a great fire in the sky” in 1582, or paintings of the sky over Kyoto in 1770—offer some clues but are open to interpretation. And while there are correlations between CMEs’ frequency and general solar activity, sunspots, and flares, they don’t seem to relate to the size or threat any storm actually poses, which makes long-term forecasting all but impossible.
Instead, astronomers have to watch and wait. More than a dozen space and weather agencies around the world have dedicated forecasting arms, which collaborate through transnational organizations like the World Meteorological Organization and the International Space Environment Service. However, the prediction window is slim: Solar storms take one to three days to reach Earth, and for most of that journey astronomers have to rely on modeling to predict size, speed, and intensity to categorize any incoming storm, much like a hurricane. Direct measurements are only possible once the cloud has traveled 99 percent of its way toward us, when it passes a small fleet of Sun-monitoring satellites near Earth. Unlike weather satellites, however, these can’t provide real-time data; astronomers often can’t see a storm has happened until afterward. (In 2012, a storm as big as the Carrington Event missed Earth by just nine days, which NASA only realized a year later.)
Once a strong storm reaches us, it all comes down to preparation. Since the turn of the millennium, an increasing number of conferences, studies, reports, and government investigations have attempted to determine how dangerous a repeat of the Carrington Event would be. Academic and military assessments tend to be more pessimistic, while energy industry groups tend to be more sanguine—a 2019 report from the Electric Power Research Institute, a U.S. energy body, for example, modeled only regional blackouts as a worst-case scenario.
Good preparation and rapid response to a solar storm will be much, much cheaper than cleaning up afterward.
Good preparation and rapid response to a solar storm will be much, much cheaper than cleaning up afterward. In May 2020, the Foundation for Resilient Societies estimated that hardening all of the electromagnetic weaknesses in the U.S. grid would cost only $2 to $3 billion, a fraction of the trillions it could cost not to. The U.S., it should be said, is hurt by the decentralization of its privately operated grids, likely making coordination during crises more difficult and expensive than somewhere like the UK, whose National Grid claims to have a fully modeled and rehearsed “Black Start” plan wherein the entire country’s power would be turned off until a storm passes, then turned on again piece by piece.
Arguably, the danger isn’t the storm itself so much as human fallibility. After all, we knew a pandemic was coming, but complacency made a novel virus feel like a surprise. Hopefully, with the lessons of the pandemic in mind, we’ll be better at recognizing urgency, preparing accordingly, and acting with the swiftness the next catastrophe warrants.
Maybe, when the next huge solar storm hits, we’ll only remember it for how beautiful the sky was at midnight—from the poles to the equator.