Emissions from the damaged Nord Stream gas pipelines are equivalent to a tenth of the UK’s annual carbon dioxide output, amounting to an “environmental crime”, experts said on Wednesday.
The natural gas pipelines, running through the Baltic Sea, began leaking after unexplained ruptures on Monday, which several countries have suggested could be the work of Russia.
The methane leaking from the pipelines, constructed to carry gas from Russia, is around 30 times as potent as carbon dioxide in terms of its greenhouse gas effects.
Danish authorities estimated that the combined leaks from Nord Stream 1 and 2, north-east of the Danish island of Bornholm, amount to the equivalent of releasing 43.8 million tonnes of carbon dioxide over a 20-year period.
That accounts for around a tenth of the annual greenhouse gas output of the UK and the entire annual emissions of Denmark.
“The Nord Stream leak is really disturbing. It is a real travesty, an environmental crime if it was deliberate,” said Prof Jeffrey Kargel, of the Planetary Research Institute in Arizona.
Russia has dismissed claims it was behind an attack on the pipelines as “stupid” after Ursula von der Leyen, the European Commission chief, said the leaks were caused by sabotage.
Dr Jasmin Cooper, of Imperial College London, said leaks from sub-sea pipelines usually have zero climate impact because the methane dissolves into the water, but the nature of the damage to the Nord Stream pipelines meant the methane was likely to be reaching the atmosphere.
On Wednesday, Germany said it was stepping up patrols to protect its critical infrastructure as secret services analysed satellite images of ship movement for clues to the suspected Nord Stream sabotage.
Federal police are tightening the security of German territorial waters, coastal patrols are being stepped up and the navy has been dispatched to the site of the explosions.
The BND, the foreign arm of Germany’s intelligence services, believes the underwater blasts were sabotage and could only have been carried out by a state actor.
One theory is that divers planted explosives on three parts of the Nord Stream 1 and 2 pipelines, which suffered “unprecedented damage” and led to three large leaks of dangerous methane that could catch fire and sink ships.
Robert Habeck, the German economic minister, said there was a risk of further acts of sabotage. “Of course, the critical infrastructure is a potential target,” he added.
German authorities believe the pipelines, once central to Russian supplies of gas to Germany and elsewhere in Europe, will never be usable again after the suspected attacks, the Tagesspiegel newspaper reported.
A German Chancellery-led crisis team is also concerned about protecting liquid gas terminals, which are vital for receiving alternative supplies to Russian natural gas. Berlin recently struck a deal for liquefied natural gas with the UAE to replace Russian supplies after the invasion of Ukraine.
The German defence ministry said naval vessels had been deployed to help in the investigation into the pipeline breaches. However, it is very difficult to carry out searches at a depth of 80 metres because of safety concerns around the leaks.
It may take as long as two weeks before an investigation into the Nord Stream leaks can begin, Morten Bodskov, the Danish defence minister, told local media before talks with Jens Stoltenberg, the Nato secretary general, on how to protect critical infrastructure.
“Russia has a significant military presence in the Baltic Sea region and we expect them to continue their sabre-rattling,” said Mr Bodskov said.
Josep Borrell, the EU’s chief diplomat, said: “Any deliberate disruption of European energy infrastructure is utterly unacceptable and will be met with a robust and united response.”
Norway was also beefing up security throughout its oil and gas sector. A Baltic pipeline, linking Norway to Poland, was inaugurated on Tuesday. The timing of the explosions and the closeness of the new pipline to the Nord Stream system has led to fears Moscow could target Norwegian infrastructure next.