by Brian Tomasik
First written: 12 Apr. 2016; last update: 12 Aug. 2017


This piece describes some ways to back up your most important electronic data against the risk of electromagnetic disasters. Since "NASA puts the likelihood of [...] a geomagnetic super-storm at 12 percent per decade", the expected benefit of making these backups seems worth the cost.

My current recommendation is to use MDISC Archive Service, combined with cloud storage (so that your data won't just be in one location) and possibly paper backup for the most crucial documents.

Types of disasters

Geomagnetic storm

This article reports:

According to [former Director of Central Intelligence James] Woolsey, a solar super-storm like the Carrington Event today would “collapse electric grids and life-sustaining critical infrastructures worldwide, putting at risk the lives of billions.”

Of course, if a geomagnetic storm was bad enough that society collapsed, then my writings would be less useful than in scenarios where that doesn't happen.

This article quotes "Doug Biesecker of the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center" as saying:

The possibility of an extreme CME causing a very powerful geomagnetic storm is real. There’s considerable uncertainty to how frequent such storms are at the level where we worry about huge impacts on the power grid and the resulting impacts that a lack of electricity would have. Is it a 1 in 50, 1 in 100, or 1 in 1,000 year event? We just don’t know.

Verge (2013) reports the recommendations of Eric Gallant: "For data center providers, Gallant urges taking precautions to prevent damage resulting from small or mid-sized solar flares. This includes installing transient voltage surge suppression (TVSS), uninterruptible power supplies (UPS), and on-site emergency standby generators." How common are TVSSs in data centers? Can data be lost if they're not in place?


An electromagnetic pulse (EMP) attack could potentially destroy electronic equipment in a wide region of the US. The probability of such an attack happening in my lifetime seems pretty low but maybe not less than a few percent?

Thibodeau (2014) discusses a company opening a data center that "has been purpose-built to protect against an electromagnetic pulse (EMP), either generated by a solar storm or a nuclear event." This suggests that most data centers aren't protected? Thibodeau (2014) says:

Domich said the idea for the EMP-resistant data center came from a customer, an insurer, that wanted to protect its data from electromagnetic pulses.

An EMP can "irrevocably destroy" data, said Domich. The magnetic field on a disk that is used to set the data, if not maintained, or if it is abruptly or intensely changed, will wipe out the data, he said.

EMP GRID Services describes an "EMP Resilient Center".

Almost no data centers are EMP-proof, so if Google/Facebook/etc. had only one copy of your data (do they?) and it was stored in an affected data center, the data would presumably be lost? Maybe this isn't true for data centers using optical storage, such as Facebook's Blu-Ray data centers (Metz 2016)? Or when most people say data centers aren't protected against EMPs, are they merely saying that the data-center would go offline, not that the data itself would be erased?

Google explains that "Rather than storing each user's data on a single machine or set of machines, we distribute all data — including our own — across many computers in different locations." But given that many of Google's data centers are in the USA, I wonder if the replicated copies of US customers' data are all in the USA and hence vulnerable to a USA-wide EMP?

EMPs can be worse than solar storms

Clark (2013) seems to imply that EMPs are more likely than solar disasters to damage computer hardware:

Although direct damage to electronics in the style of an electromagnetic pulse (EMP—one of the “side effects” of a nuclear blast) owing to a solar flare is conceivable, it is less likely. “An EMP is a sudden, high-intensity event, whereas a solar storm is a longer-duration, lower-intensity event. Because of these different electrical characteristics, solar storms will typically only generate currents in very long (300 km+) conductors. Hence, technologies that are vulnerable to solar-storm damage include large systems, such as electrical grids, transcontinental pipelines and telephone systems,” said Gallant. “As a result, the electrical and communication systems that data centers depend on are much more likely to be affected by a solar storm than the data center IT infrastructure itself.”

Hedge fund manager Paul Singer wrote in an investment-update letter warning about electromagnetic disasters that a deliberate EMP attack "would not cause any blast or radiation damage, but such an attack would have consequences even more catastrophic than a severe solar storm. It could not only bring down the grid, but also lay down a very intense, very fast pulse across the continent, damaging or destroying electronic switches, devices, computers and transformers across America" (Delevingne 2014).

Woolsey and Pry (2015): "Nuclear EMP is worse than natural EMP and the EMP from [Radio-Frequency Weapons] RFWs because it combines several threats in one. Nuclear EMP has a long-wavelength component like a geomagnetic super-storm, a short-wavelength component like Radio-Frequency Weapons, a mid-wavelength component like lightning--and is potentially more powerful and can do deeper damage than all three."

Backup options

Is a flash drive enough?

This article says that "A flash drive stored well away from any external electrical lines would very likely survive an EMP strike." One commenter on this thread echoes that "Flash drives and optical disks would be completely safe too." However, other people on that thread use Faraday cages -- is that because Faraday cages actually are necessary to protect a flash drive?

Backup across continents

For a local EMP, an easy solution could be to send a duplicate flash drive to a friend on another continent (maybe only once every decade or whatever, to reduce the annoyance of doing so). One answer here recommends this solution, but only for "Events much less severe as the Carrington event".

Woolsey and Pry (2015) say "The Carrington Event was a worldwide phenomenon". Does this mean that a Carrington-sized storm would cause severe damage worldwide? Or would it still be mostly concentrated on one side of the planet?

Faraday cages

TODO: I plan to look more into how to buy a Faraday cage.

One concern I've seen discussed is that the cage itself my destroy the contents of a flash drive. So it seems prudent to have two copies of your data: one on a flash drive stored in a Faraday cage, and one on a flash drive not in a Faraday cage.

One answer here says that for big enough geomagnetic storms: "Theoretically, if your Faraday cage is good enough (enough layers, thick enough conducting layers), it might pull it off. But I'm not sure if that will work with such violent events."

Optical storage (CDs, DVDs)

Someone on this forum suggests: "Files can be put in encrypted 7z archives before giving to friends to store. as a CD is an optical medium (hard drives are magnetic, USB drives use 'flash memory') it can survive electromagnetic hazards better than other types of storage, it ought to survive EMP or [coronal mass ejection] CME."

One answer here says that CD/DVD storage is "The best solution" and would work even for "Events similar or bigger than the Carrington event".

Many new laptops don't have CD drives, but you can buy an external USB drive.

Unfortunately, regular CDs/DVDs don't last indefinitely:

It is hard to predict exactly how long an optical disc will last since it depends on so many different factors. Nevertheless, estimations are floating around that predict a life span of up to 200 years for recorded CD-Rs and Blu-Ray discs. The shortest life span with 5-10 years is predicted for unrecorded CD-Rs and CD-RWs, followed by recorded DVD-RWs with up to 30 years. Recorded CD-RWs and DVD-Rs have a predicted lifetime of 20-100 years. In other words, you should not rely on any of these media for lifelong storage of your precious data, as they are likely to fail sooner rather than later.


The longevity problems of regular optical disks are overcome by the M-DISC, which claims to last 1000 years. This article says that the M-DISCs tested could be read by 6 out of 8 of the DVD drives tested. However, a comment on that article claims that "MDISC is mostly marketing hype" and "the government recognizes that standard Blu-Ray are just as acceptable."

This article says "If you’re worried about optical drives disappearing, know that optical retains a very strong presence in the archival community, as well as the enterprise, so that should give you some reassurance."

Printing out on paper

You can collect the texts that you most want to save and have them printed out (probably by a professional printing service to avoid wearing out your home printer). Printed pages can get lost, may burn up in a house fire, etc., but their risks are pretty complementary to the risks that electronic data storage faces. (It's good to have at least one cloud backup and at least one in-your-home backup.)

Paper is nice because it avoids "black swans" of digital preservation—not just geomagnetic storms but also bit rot, format rot, lack of electricity, etc. Paper copies of documents aren't as flexible as digital data, but the pages could be scanned back to electronic format and converted to text using OCR if need be.

A Reddit comment says:

The absolute best defense against bit rot is to have multiple copies of your important data spread across different storage mediums in different locations.[...]

If you have data in text files that will not change, old school low tech printing it on paper with a laser printer and NOT an inkjet printer works great. Paper, under the proper storage conditions has been known to survive hundreds and in some cases, thousands of years. If you need to get it back into a computer in digital form, you can use OCR to re-digitize it quickly and accurately.

For a how-to guide on paper website backups, see "Backing Up a WordPress Website on Paper".

Backing up other people's websites

Internet Archive?

Usually you can get backups of other people's websites through Internet Archive. But would Internet Archive's data survive a Carrington Event-scale geomagnetic storm?

The answer here says "The main Internet Archive storage is a custom technology called the PetaBox, which is now in its second generation. It’s designed and built from the bottom up and the inside out to be pretty robust." But I'm currently not sure whether PetaBox storage would be resistant to a Carrington Event. (I'd like to explore this further.)

This answer, regarding Internet Archive's protection against EMPs, says Internet Archive uses "Globally distributed backups." But I'm not sure if this is sufficient protection against a Carrington Event.

There also remains some risk that Internet Archive will go away eventually, perhaps due to lack of funding, though one hopes that its content would remain accessible to those willing to pay for access. And Internet Archive doesn't always have 100% coverage of pages on a given domain.

Doing your own backups

In order to be on the safe side, I do my own backups of websites whose content I consider important. Many entire websites are less than 1 GB when compressed, which makes backing up hundreds of them potentially feasible, given that the M-DISC service mentioned above has a huge size limit: "The overall limit for our $8 [per month] plan is 1TB of data per year. If you plan to upload more than that in a year, we suggest you consider our Pro Plan".

This page gives some details about doing website downloads to back up other people's websites (or your own website).