Size of Nord Stream blasts equal to large amount of explosive, UN told

<span>Photograph: AFP/Getty Images</span>
Photograph: AFP/Getty Images

Denmark and Sweden have said leaks from the Nord Stream pipelines in the Baltic Sea were caused by blasts equivalent to the power of “several hundred kilograms of explosive”.

The conclusions were made in a joint report by Denmark and Sweden which was delivered to the United Nations. The UN environment programme said on Friday the ruptures are likely to have led to the biggest single release of climate-damaging methane ever recorded.

German authorities have also said they believe that highly explosive detonations were responsible for the sabotage attacks on the two pipelines. The EU, Nato and the governments of Poland, Sweden and Denmark have all said they believe the leaks were caused deliberately.

Data analysis has revealed huge clouds of methane gas are hovering over the leaks, from natural gas that has been pouring into the Baltic Sea from both pipelines since Monday, the ICOS, a greenhouse gas observation system operating across Europe, reported.

The pipes, built to transport gas from Russia to Germany, and only one of which was ever activated but both of which were full of gas, are said to be unusable due to the damage caused by the ruptures.

Intelligence sources quoted in the news magazine Spiegel believe the pipelines were hit in four places by explosions using 500kg of TNT, the equivalent to the explosive power of a heavy aircraft bomb. German investigators have undertaken seismic readings to calculate the power of the blasts.

Related: Nord Stream attacks highlight vulnerability of undersea pipelines in west

The first signs of explosions were registered on Monday morning by a Danish earthquake station after suspicious activity in the waters of the Baltic Sea. A monitoring station on the Danish island of Bornholm measured severe tremors.

A representative of the Swedish coastguard told AFP: “There are two leaks on Swedish territory and two on the Danish side.”

It remains a mystery as to how the explosives reached the pipeline. According to initial reports, the explosions happened at depths of between 70 and 90 metres.

There has been speculation that mini submarines might have been used to deliver the explosives. However, the amount of explosives that would have been necessary to cause such large blasts make this theory increasingly unlikely.

Instead, experts are suggesting that maintenance robots operating within the pipeline structure may have planted the bombs during repair works.

If this theory proves to be right, the sophisticated nature of the attack as well as the power of the blast would add weight to suspicions that the attacks were carried out by a state power, with fingers pointed at Russia. Moscow has repeatedly underlined its capability to disrupt Europe’s energy infrastructure.

On Friday, Vladimir Putin blamed the US and its allies for blowing up the pipelines, raising the temperature in the crisis. Offering no evidence for his claim, the Russian president said in a speech to mark the annexation of four Ukrainian regions: “The sanctions were not enough for the Anglo-Saxons: they moved on to sabotage. It is hard to believe but it is a fact that they organised the blasts on the Nord Stream international gas pipelines.”

The methane clouds are being monitored closely. The ICOS, which is analysing the air quality, has shown footage of a huge gas cloud hovering above the Baltic Sea and moving across Europe.

Methane measuring stations in Sweden, Norway and Finland had indicated sharp rises in methane in recent days. Observation satellites are believed to have failed to record the emissions due to cloudy weather, the ICOS said.

It said the emissions were equivalent to an entire year’s methane output for a city “the size of Paris or a country like Denmark”.

“This is really bad, most likely the largest emission event ever detected,” Manfredi Caltagirone, acting head of UNEP’s International Methane Emissions Observator told Reuters. “This is not helpful in a moment when we absolutely need to reduce emissions.”

Prof Stephen Platt, from the Norwegian Institute for Air Research, said: “We assume the wind on the leak area blew the methane emissions north until the Finnish archipelago, then bent towards Sweden and Norway.”

Germany’s federal environment agency has estimated that emissions equivalent to 7.5m tons of CO2 have been released into the atmosphere. That equates to about 1% of Germany’s entire annual emissions. Gregor Rehder, of the Leibniz Institute for Baltic Sea Research in the northern town of Warnemünde, told Spiegel: “That is quite a considerable amount of greenhouse gas that has been released.”

Methane is one of the strongest greenhouse gases, warming the atmosphere about 30 times more than carbon dioxide over a period of 100 years. The timing and scale of the leak should be viewed with even more alarm owing to the immediate necessity to slow down climate change, the ICOS said.

German investigators told media that divers or remote-controlled robots may be able to visit the site of the leaks as early as this weekend.