A Carrington-level solar storm today could knock out power grids for months, and one is overdue

In late summer of 1859, the Sun hurled a colossal burst of charged particles directly at Earth, and the planet’s fledgling electrical technology paid the price. Telegraph networks — the era’s cutting-edge communications grid — sparked, failed, and in some cases kept transmitting even after operators disconnected the batteries, running on current induced by the storm itself. Auroras normally confined to the poles blazed over the Caribbean. That episode, now known as the Carrington Event, remains the benchmark for the most intense space weather in recorded history, and it looms over a stark modern question: what would a storm of the same magnitude do to a civilization that now runs on continent-spanning power grids and orbiting electronics?

What the Sun did to Earth in September 1859

The event is named for Richard Carrington, a British astronomer who was sketching sunspots when he watched an intense flash erupt from the solar surface — one of the first observations linking a solar flare to effects felt at Earth. A coronal mass ejection, a vast cloud of magnetized plasma, followed and slammed into the planet’s magnetic field with unusual speed and strength.

The National Oceanic and Atmospheric Administration’s account of what happened in 1859 describes telegraph systems thrown into chaos, with sparking equipment starting fires and lines behaving erratically. The geomagnetic disturbance was so severe that the northern lights were reported far into the tropics. Because there were no power grids, satellites, or electronics to speak of, the damage was limited to the telegraph. The same storm today would land on a very different world.

How a modern grid fails when the Sun overloads it

The threat to contemporary infrastructure comes from geomagnetically induced currents. When a powerful solar storm distorts Earth’s magnetic field, it drives rogue electrical currents through long conductors — high-voltage transmission lines, pipelines, and rail networks. Power grids are especially vulnerable because their large transformers are designed for alternating current, and the slow, direct-current-like surges from a geomagnetic storm can push them into saturation, overheating their cores.

The danger is not merely a temporary outage. High-voltage transformers are enormous, expensive, and often custom-built, with manufacturing lead times measured in months to years and few spares held in reserve. If a severe storm were to damage many of them at once across a wide region, restoring power could take far longer than after an ordinary blackout. That is the mechanism behind the warning that a Carrington-class storm could darken grids for months rather than hours, and it is why space weather is treated as an infrastructure-security issue and not just an astronomical curiosity.

The trillion-dollar price tag of a direct hit

Assessments of a worst-case strike run into the trillions. Analyses cited in coverage of the Carrington Event point to a National Academies of Sciences study estimating that an extreme storm could inflict damage on the order of $1 trillion to $2 trillion in its first year and disrupt telecommunications, banking, GPS, and the power grid, with a much-quoted worst-case putting full recovery at four to ten years. Those figures represent a severe upper bound, and researchers openly disagree about how catastrophic the real outcome would be, since grid operators have hardening measures and emergency procedures that did not exist in earlier estimates.

Even short of the doomsday scenario, lesser storms carry real costs. The cascading dependencies of modern life — payment systems that need precise timing signals, aviation that relies on satellite navigation, supply chains that assume the lights stay on — mean that disruptions ripple outward from the grid into nearly every sector. The uncertainty is less about whether a great storm would hurt and more about how deep and how lasting the wound would be.

Why scientists say a great storm is statistically “overdue”

The recurrence of Carrington-scale events is estimated at roughly once every one to five centuries, though such statistics come with wide error bars given how few extreme storms have been directly recorded. By that measure, more than 165 years without a comparable direct hit is enough for some analysts to call another one “overdue,” in the sense that the calendar has run well past the average gap since 1859.

The planet has also had close calls that underscore the risk is not hypothetical. In July 2012, a coronal mass ejection judged comparable in strength to the 1859 storm swept across Earth’s orbital path — but at a point where Earth was not in the line of fire, missing by roughly a week. Had it erupted days earlier, it would have struck a fully wired planet. Space-weather specialists cite that near-miss as evidence that the Sun remains capable of producing Carrington-level outbursts in the modern era; the difference between a headline and a global crisis was orbital timing.

The watch kept on the Sun, and what preparation looks like

Forecasting has become a routine government function. NOAA’s Space Weather Prediction Center issues the operational alerts and forecasts that grid operators, airlines, and satellite fleets rely on, drawing on a fleet of solar-monitoring spacecraft and ground observatories. Instruments stationed between the Sun and Earth can provide a short window — often tens of minutes to a day, depending on the storm — between detecting an incoming cloud and its arrival, enough time to take protective action if plans are ready.

That broader effort to watch threats approaching from space is part of the same sky-monitoring mission that spans NASA’s hazard-tracking work. Preparation on the ground focuses on hardening the grid: installing devices that block induced currents, keeping spare transformers, and rehearsing the operational steps to shed load and isolate vulnerable equipment when a severe storm is forecast. None of it can stop the Sun from erupting. The goal instead is to shrink the gap between what a Carrington-level storm could do and what a prepared civilization would actually suffer.

This article was researched and drafted with the assistance of AI and reviewed before publication.

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