Large volumes of the potent greenhouse gas methane are estimated to be leaking into the atmosphere from damaged European pipelines stretching from Russia to Germany that several EU leaders have said were sabotaged.
While the precise volume of methane escaping into the atmosphere from underwater pipelines is difficult for scientists to quantify with certainty, experts say the amount estimated to be coming from four leaks detected in the Nord Stream pipelines is likely to be significant.
If only one of the two leaking pipes were to release all their contents, it would represent about twice as much methane as was emitted during the 2015 Aliso Canyon leak from underground storage in California, one of the worst ever recorded, said Paul Balcombe, honorary lecturer at Imperial College London in chemical engineering.
Methane is the main component in gas and is a key driver of climate change. The molecule traps more heat over a shorter time period than carbon dioxide, giving it about 80 times the warming potential of carbon over 20 years.
It behaves differently when released into seawater than directly into the atmosphere. Some of the methane that leaked would be dissolved in the ocean, although the huge surface bubbles in the Baltic Sea indicated that much was rising to the surface and escaping into the atmosphere.
“It’s a pretty big deal,” said Balcombe, noting the leaks “all look pretty big, they’re showing quite a wide diameter.”
The German environment agency estimated on Wednesday that the leaks would release 300,000 tonnes of methane into the atmosphere.
By comparison, the Aliso leak emitted around 100,000 tonnes of methane into the atmosphere between October 2015 and February 2016.
Annual global methane emissions are around 570mn tonnes, the International Energy Agency estimates, making the Nordstream leak potentially a fraction of the overall amount while highlighting the risks.
“It’s impossible to pin a number on [the Nord Stream leaks] right now,” but they “could be as significant as [Aliso],” said Balcombe. However, he said that it was unlikely that the pipes would release their entire contents.
Jean-Francois Gauthier, vice-president of measurements and strategic initiatives at the global emissions modelling service, GHGSat, said that “by any measure, this is a catastrophic level.”
“It is especially unusual to see over such a short period of time, and the likely environmental impact will be similar to at least 1mn cars on the road for a full year,” Gauthier said.
Grant Allen, professor of atmospheric physics at the University of Manchester, said the impact of the disaster for the climate would be limited by the fact that the pipelines were not in operation even if they still contained gas, which would reduce the amount that escaped.
Ocean bacteria can break down methane using oxygen, a process that produces carbon dioxide which dissolves in the water. Although the world’s oceans absorb carbon emissions, the volume they are taking in as a result of the build up of greenhouse gases is causing them to acidify.
Satellite imagery services that can identify and quantify methane leaks have encountered difficulties in analysing the Nord Stream leaks due to cloud cover. Erik Arends, from the SRON Netherlands Institute for Space Research, said that assessing the damage was challenging because the water did not reflect enough sunlight to produce useful images.
Giant bubbles of gas were first spotted in the Baltic Sea on Monday, which led to the discovery of leaks in two Nord Stream pipelines, located in international waters just off the Danish island of Bornholm.
The discovery has fuelled speculation about vandalism by Russia, which the Kremlin has denied, and intensified discussions about the need to secure Europe’s energy networks.
Ursula von der Leyen, the European Commission president, said on Tuesday that “sabotage action” had taken place and “any deliberate disruption of active European energy infrastructure is unacceptable and will lead to the strongest possible response”.
The cause of the leaks remains unknown, though an official investigation has been announced by Denmark and Sweden.
The issue is due to be discussed at a meeting of EU energy ministers in Brussels on Friday.
“I believe everybody around the table is deeply concerned about this matter. Safety and environmental concerns are an utmost priority for all of us . . . We all agree that we need to support investigation and get full clarity on this,” said a senior EU diplomat.
Jeffrey Kargel, from the Planetary Research Institute in Arizona, said the damage was “really disturbing,” and amounted to “an environmental crime if it was deliberate.”
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