As the Iberian Peninsula recovers from one of the biggest power outages in recent history, theories about its cause sweep across news outlets and social media.

Around midday yesterday (29 April), Spain and Portugal experienced a mass power outage that affected the entire Iberian Peninsula, thrusting both countries into states of emergency.

The blackout – which also briefly affected parts of France – caused considerable disruptions for both countries, bringing transport systems such as trains to a halt and leaving millions of people without phone and internet coverage or access to services such as ATMs.

Traffic lights stopped working, hospitals were forced to rely on generators and planes were grounded in one of Europe’s worst power outages in recent memory.

In Spain, reports indicate that the country had suffered a loss of 15GW of electricity generation in five seconds – an occurrence that University College Dublin’s Dr Paul Cuffe described as a “nightmare scenario”.

While power has now been restored to most of Spain and Portugal, the two countries are now looking into what caused the massive outage. Authorities in both Spain and Portugal are investigating a number of possibilities and theories, with Spanish prime minister (PM) Pedro Sanchez stating that his administration is “not ruling out any hypothesis”.

Cyberattack fears

With a blackout of such scale, one of the initial theories suggested that the outage was caused by a cyberattack.

The Portuguese government and Spain’s national grid operator have since concluded that a cyberattack was not responsible for the outage. However, it seems that the theory is not being completely discarded so far.

Spain’s top criminal court announced today that it was investigating whether the blackout was “an act of computer sabotage on critical infrastructure”, with judge José Luis Calama emphasising that an act of “cyber terrorism” cannot be ruled out.

Commenting on the cyberattack theory, global cybersecurity advisor at ESET Jake Moore said that the situation “brings to life the long-feared worry of what an attack on delicate national infrastructure systems would look like”.

“When looking for the root cause, it is good practice to think of all the possibilities. Nation state attacks are notoriously difficult to defend against and targeting critical infrastructure has always been one of the biggest threats to a country,” he said. “The level and sophistication in cyberattacks has dramatically increased in recent years with the added use of artificial intelligence, but when combined with sheer relentless determination for success, it is all the more difficult to defend against.”

Climate challenges

As well as cyber terrorism, another top hypothesis being considered is the possibility of a weather or climate-related cause.

Patrick Galey, interim head of FF investigations at Global Witness, stated that although no cause has been confirmed so far, it is widely known that the effects of the climate crisis continue to put strain on electricity grids.

“Governments should take this as a wake-up call on the need to invest in renewable technology, which is already cheaper nearly everywhere than more oil and gas, in order to future-proof the grids that people need to live happy, healthy and secure lives,” said Galey.

“Importing oil and gas from petrostates will not ready us for what is to come, but resilient, clean energy will.”

Misinformation worries

Early reporting on the blackout circulated a purported statement from Portuguese electricity operator Redes Energéticas Nacionais (REN) that claimed “induced atmospheric vibration” caused by extreme weather variations played a part in the shutdowns.

However, just today, a spokesperson for REN reportedly told AFP news agency that the organisation did not put out the statement.

Further to this, Spain’s national meteorological office – Aemet – released a statement that it had not detected any unusual meteorological or atmospheric phenomena yesterday.

Other incidents of misinformation began to spread in the immediate aftermath of the outage, including a false narrative claiming that European Commission president Ursula von der Leyen had accused Russia of a cyberattack – which was shut down by the European Commission’s chief spokesperson Paula Pinho.

In his speech concerning the blackout, Spain’s PM stressed the importance of seeking information through “official channels” and to avoid speculation.

He added that crisis situations such as the blackout set “the perfect conditions for misinformation and hoaxes”, as he urged people “not to spread information from dubious sources”.

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