Experts say that the unexplained explosions in the Nord Stream pipelines running from Russia to Europe could release an “unprecedented” amount of the greenhouse gas methane and be enormously damaging to the climate.
More than 100,000 metric tons of natural gas are bubbling on the surface of the Baltic Sea over a 1-kilometer (0.6-mile) area, leaking into both the water and the atmosphere. Around 90% of that is methane, a greenhouse gas with more than 80 times the global warming power of carbon dioxide (CO2).
That’s comparable to the infamous Aliso Canyon leak in the United States in 2016, which released 97,000 tons of methane into the open air. The difference is that leak was more gradual, occurring over a much longer period.
The worry with Nord Stream is the event could be so large and rapid that it adds a huge chunk to the world’s emissions of methane, which is already escaping in enormous volumes from gas, oil and coal infrastructure, and has a quick warming effect on the planet.
The leak was discovered earlier this week and seismologists said they detected explosions at the site, which probably caused the pipelines to rupture. On Thursday, Sweden’s coast guard confirmed a fourth leak in the pipelines. One of its vessels near the source of two leaks that are in Swedish waters is reporting a steady flow of gas to the surface.
There are still many unknowns around what happened to the pipelines, which have been used as bargaining chips during the energy crisis and Russia’s war in Ukraine. Who is responsible, as well as geopolitical, economic and security questions, remain unanswered.
“We’re very worried,” said Zitely Tzompa Sosa, an atmospheric scientist at the Clean Air Task Force (CATF), a climate non-profit organization.
Based on data from Nord Stream AG, the operator of the pipelines, Tzompa Sosa says that that between 100 and 120 kilotons of methane were probably in Nord Stream 1 at the time of the rupture.
“That would be equivalent to about a third of Germany’s total methane emissions from the energy sector in 2020, which is about 5% of Europe’s methane emissions from the energy sector,” Sosa told CNN, assuming the greenhouse gas entered the atmosphere.
Quantifying the leak at the moment is a rough estimate. Nord Stream 1 stopped supplying gas to Europe in July and Nord Stream 2 never fully opened, making certainty about the volume impossible.
Other climate scientists are less conservative in their estimates. Although Nord Stream 2 never fully opened, the pipe has a capacity of 200 kilotons.
Paul Balcombe, a lecturer in chemical engineering at Imperial College London, told CNN that 200 kilotons of gas entering the atmosphere would equate to about 10% of the UK’s total methane emissions.
Methane and CO2 are both greenhouse gases, but they behave in different ways. Balcombe told CNN that methane is a far greater risk to “near-term warming” than CO2. Although methane only lasts “around 10 years in the atmosphere,” its immediate impact is “much more potent.”
But even in the longer term, it’s still worse.
“Over an average of 100 years, it’s about 30 times worse than CO2,” Balcombe told CNN, referring to methane’s warming power. As governments scramble to reduce their emissions, “causing these big leaks right now is going to worsen near-term warming.”
Why methane leaks matter
Gas leaks are much more harmful to the climate than simply burning gas for use. The raw molecular form in which the methane leaks from the pipes and enters the atmosphere is worse than if the gas had been used in homes, for example, for heating.
When methane is burned, for instance in domestic kitchens, “the compounds that are released from the combustion are not as dangerous to the climate as methane itself,” Tzompa Sosa said.
Rowan Emslie, a spokesperson at CATF, said many gas production factories had “safety systems” designed to burn any gas that escaped in a leak, since this is preferable to allowing the raw methane to enter the atmosphere.
“It’s still CO2 emissions, it’s still bad – but it’s not nearly so bad,” Emslie told CNN.
It’s really the pace at which the gas has entered the atmosphere that is concerning.
“The unprecedented aspect is that we don’t think we’ve seen a leak this large, this fast before,” Emslie said, “which is why it’s so worrying.”
The fact that the Nord Stream leaks occurred underwater complicates understanding further. Factors as varied as the size of the gas bubbles, the concentration of methane-eating microbes in the water, and the depth from which the gas traveled upward, can all affect the overall environmental impact. Monitoring the emissions will also be difficult, as most satellites only capture methane concentration over land, rather than in the sea.
Understanding the full picture will “take a little bit more time – months, potentially years,” Sosa said.
The event itself may be over quite quickly. Grant Allen, an environmental scientist at the University of Manchester, stressed to CNN this is a “time-limited event.”
If the flow of gas has been shut off, as Russia has claimed, the pace at which it is released will slow as the pressure in the pipes drops. In this case, the sea will not be “boiling” for much longer.