The Carrington Scenario

Alastair Isaacs
Oct 5, 2020 · 8 min read
Image for post
Image for post

Across half the planet power grids suddenly surge. Currents and voltages fluctuate wildly, threatening to overwhelm vital equipment. Before long electrical networks start falling — and the world plunges into a blackout without historical precedent.

The damage to the power system takes months to repair. Without reliable access to electricity, the lifeblood of modern existence, society and the economy grind to a halt. Financial markets crash as the lack of electricity interrupts food, fuel and transportation services. Within weeks, economic collapse, global unrest and mass starvation are unavoidable.

This, the Carrington Scenario, might seem catastrophic, but it is almost certain to happen in the next few decades. The culprit is our Sun, which though mostly benign and life-giving, is bound to occasional fits of violent temper. Every now and then, following an eleven-year cycle of activity, the Sun hurls vast clouds of super hot and highly magnetic material into space.

Only a fraction of these clouds, or solar flares, are aimed at Earth, and even when they are, they are often small enough to be ignored. Indeed, one by-product, the aurora, or northern lights, is spectacular enough to be welcomed. But rarely, perhaps once every hundred years or so, the Sun slings an exceptionally vast and powerful cloud towards the Earth.

The result is an incredible auroral display, sometimes, like the display of 1859, visible across the planet and bright enough to read by. The flare of 1859 is notable for another reason: it was the most powerful such event known in recent history, and the first time humanity saw the terrible impact on electrical technology.

That flare was not without warning. During the summer of 1859 astronomers recorded unusual activity on the Sun. Large numbers of sunspots — historically linked to a more active star — appeared. At the end of August observers across the world watched startlingly bright aurora. Newspapers spoke of brilliant displays across northern Australia and the United States. Sailors in the Pacific Ocean wrote of the night sky in awestruck tones.

‘‘The whole heavens became brilliantly illuminated’’

Report from the Savannah in the North Atlantic

The nights that followed were dramatic. On September 1, Richard Carrington, for whom the 1859 event is often named, spotted two patches of bright light breaking away from the Sun. He calculated they were moving with extraordinary speed — covering 35,000 miles as he watched.

A day later those patches of light, in reality large chunks of highly magnetic solar plasma, hit the Earth. Aurora were again seen across the planet, even in countries close to the equator. The night sky was so bright that some mistook it for the dawn light. In North America the illumination of the aurora was enough to read by.

Telegraph operators, working on early communications networks spanning Europe and North America, reported astonishing things. In Europe magnetic disturbances drove wild and uncontrollable electrical currents across the network. For hours communications between the European capitals completely halted. In America operators saw overloaded equipment sparking, and in some places catching fire. Other operators cut the power supply to the lines — but were astonished to find that they could still communicate on the power of the aurora alone.

In 1859, electrical technology was in its infancy. The impact from the massive flare that hit the Earth that year was, thanks to this, mercifully limited. But another such flare will, sooner or later, strike our planet. And next time, because of the electrical infrastructure now spanning the globe, the effects could be devastating.

Telegraph networks across Europe in 1859 (Stevens et al. 2012)

Powerful solar flares are harmful for one reason: the strong magnetic and electric fields they carry with them. Fortunately for us, the Earth has an inbuilt shield. The swirling molten iron core of our planet creates a powerful, but normally invisible, magnetic sphere around the world. This shield is more than capable of dealing with the usual stream of magnetic particles coming from the Sun. Indeed, the only sign that they are there at all comes from small auroral displays around the poles.

But when a powerful solar flare hits the Earth this shield is no longer strong enough to protect the surface. Magnetic and electrical disturbances then sweep the planet. In pre-industrial times, this was not too much of a problem; but now, with electrical cables stretching for thousands of miles, these disturbances can result in energetic surges across power networks.

That would be bad news for transformers, the expensive equipment that lies at the heart of modern power grids. Uncontrolled electrical surges cause transformers to heat up, damaging or destroying the crucial components. If a large enough flare hits the Earth, wild electrical surges would destroy hundreds of transformers. This would be enough to collapse power grids and leave tens, or even hundreds, of millions without power.

It would be an unprecedented blackout, but even worse, it would be long lasting. Transformers take months to build, and replacing hundreds of them at once would be an enormous task. In a worst case scenario, entire continents would be left without power for months on end. The consequences for modern society are almost unimaginable.

There has been another big change in technology since 1859: the rise of space-based infrastructure. Our planet is now ringed by satellites doing all sorts of crucial things, from communications to weather monitoring to GPS navigation systems. A solar flare could take all these services down almost instantaneously. The loss of GPS systems would be particularly troubling —modern aircraft often rely on GPS to land safely, and shipping companies need GPS to track food containers.

Image for post
Image for post
A solar flare — the bright spot near the centre of the image — explodes away from the solar surface. Image credit: NASA Goddard

The origin of solar flares is still not well understood. We do know that the Sun follows an eleven year cycle, alternating between periods of low and high activity. Though solar flares can happen at any time during the cycle, they are much more likely to happen during the active years. The current cycle hit a minimum around the end of 2019, and will probably hit a maximum sometime between 2023 and 2026.

Even when a flare does happen, it is not always directly aimed at the Earth. Most of the time, in fact, the Sun’s outbursts pass us harmlessly by, heading out into deep space. One such massive flare occurred at the end of October 2003, mostly missing the Earth. Even so, observers as far south as Florida saw auroral displays, and the flare left at least three satellites damaged.

Fourteen years earlier, in March 1989, another flare had erupted from the surface of the Sun. It, too, passed harmlessly by the Earth. But then, three days later, a second enormous flare burst out. Travelling at over a million miles per hour, it was heading straight for Earth. Ninety hours later, during the early morning of March 13th, the storm arrived.

Aurora were again seen, sparking fears of a nuclear attack. Satellites failed or tumbled out of control. Astronauts on the space shuttle saw their instruments record mysterious and alarming values. But the most severe effects were seen in North America’s power grids. In one incident a transformer in New Jersey — handling power from a nearby nuclear power plant — overheated and was permanently damaged.

In Quebec wild swings in the power grid caused vital components to overload. In just 90 seconds half the province lost electrical power. Moments later, struggling to cope with rapid power shifts, the rest of the network collapsed. For nine hours, enduring temperatures below freezing, over six million people were left without power.

The 1989 flare, along with others that hit in 1972 and 2000, were minor events compared to those of 1859. Thanks to solar records kept since the eighteenth century, astronomers know roughly how often these small flares happen. But bigger flares are rare enough that these records aren’t long enough to do the same. Do they happen once a century, or once a millennium? And just how big can they get?

To answer these questions, astronomers turned to the polar ice sheets. Ice laid down in blizzards hundreds or thousands of years ago keeps a record of past atmospheric conditions. Big flares affect the composition of the atmosphere, boosting the levels of certain elements. By drilling deep into the ice sheets and looking carefully, scientists can find traces of these elements and a record of historic flares.

The ice record shows two things. The first, that flares like that of 1859 are relatively rare, happening only once every few centuries, is good news. But the second, that even bigger flares have happened, is more worrying. Researchers scanning through the ice found evidence that at least three huge flares have hit the Earth in the last three thousand years. The ice record is sometimes patchy, so other huge flares might still have been overlooked.

The aurora over Canada, captured from the International Space Station. Image credit: NASA JSC

The ice doesn’t reveal everything. We know that something big hit the Earth in 774AD, and again in 993AD, but whether that was really a solar flare is still unclear. The event of 774 is particularly intriguing. The spike in the ice record is the biggest in at least ten thousand years. Historical records are sketchy. Some speak of bright lights seen in the sky that year — but whether that means an aurora, or something else, remains to be seen. One alternative explanation is a nearby supernova, which would have blasted the Earth with a wave of radiation. But, until now, astronomers have failed to find any plausible candidate star.

Either way, the implications are clear. Major magnetic disturbances have happened before. They will happen again. The world, and its power grid operators, needs to prepare, or face catastrophe.

Some steps towards doing this have already been taken. Since 1996 the SOHO spacecraft has been continuously monitoring the Sun, providing a few hours notice of incoming flares. Other spacecraft have since joined SOHO, giving us ever more detailed views of our star. With warnings from these systems electrical power operators now have some time to protect vulnerable parts of the grid.

Beyond just monitoring the Sun, power operators can also harden electrical systems. New equipment can be installed to absorb or redirect power fluctuations. But this costs money. Estimates vary, but most put the price tag somewhere around $10–20bn for the US grid alone. To date, operators have made some efforts to harden grids, but they certainly aren’t enough to handle a big flare.

Compared to the phenomenal damage such a flare might cause, the cost of preparing is small. But, like with many other rare disasters, humans often prefer to ignore predictable events. Humanity has so far been lucky that no major flare has hit the Earth since electrical networks spread across the world. That luck will not last.

As if to underscore that point, on July 23rd, 2012, the surface of the Sun exploded in a massive flare, comparable, or perhaps even larger, then the 1859 event. Fortunately, the flare just missed the Earth, but not by much. If the planet had been just nine days later in its orbit, our luck might finally have run out.

Dialogue & Discourse

News and ideas worthy of discourse.

Alastair Isaacs

Written by

Once I studied physics and distant galaxies. Now I fly satellites instead, and spend my time thinking and writing about trends in space and technology.

Dialogue & Discourse

News and ideas worthy of discourse. Fundamentally informative and intelligently analytical.

Alastair Isaacs

Written by

Once I studied physics and distant galaxies. Now I fly satellites instead, and spend my time thinking and writing about trends in space and technology.

Dialogue & Discourse

News and ideas worthy of discourse. Fundamentally informative and intelligently analytical.

Medium is an open platform where 170 million readers come to find insightful and dynamic thinking. Here, expert and undiscovered voices alike dive into the heart of any topic and bring new ideas to the surface. Learn more

Follow the writers, publications, and topics that matter to you, and you’ll see them on your homepage and in your inbox. Explore

If you have a story to tell, knowledge to share, or a perspective to offer — welcome home. It’s easy and free to post your thinking on any topic. Write on Medium

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store