Leaks caused by explosions on the Nord Stream 1 and 2 gas pipelines in the Baltic Sea are releasing methane, a potent greenhouse gas. But while the incident is expected to have only a limited impact on the climate, it illustrates the risk of these emissions, experts say.
The pipelines were not in operation due to the war in Ukraine, but still contained large quantities of gas. And according to the Danish authorities, off the coast of which the damage occurred, the leaks will continue until the gas is used up, which should take “at least a week”.
Experts are still debating the volumes that could be released but point out that these leaks illustrate the danger of greenhouse gases produced by human activity, which are responsible for global warming.
“If it was deliberate, it’s an environmental crime,” says Jeffrey Kargel of the Planetary Research Institute in Arizona. “But while the amount of gas coming from the pipeline is obviously significant, it’s not the climate disaster you might think it is.”
What is leaking?
Natural gas is mainly composed of methane, whose warming effect is 28 times greater than that of CO2 over a 100-year horizon. It is considered to be responsible for almost one third of the global warming already recorded. However, its lifetime in the atmosphere is relatively short, about ten years, compared to decades or even hundreds of years for CO2.
When it comes into contact with water, some of this methane will oxidize and turn into CO2, explains Grant Allen, professor of atmospheric physics at the University of Manchester in the UK. “But given the strength of the leak, most of the gas will come to the surface as methane,” he warns.
In what quantity?
This is the main uncertainty. Experts and NGOs are working to calculate the possible capacity of the pipes at the time of the damage.
One estimate, cited by Professor Allen, puts the amount of natural gas in Nord Stream 2 at 177 million m3. The equivalent of the annual consumption of 124,000 British households.
The NGO Greenpeace uses a similar estimate to calculate that the three leaks could in total equal the equivalent of 8 months of greenhouse gas emissions from Denmark.
Paul Balcombe, Honorary Professor in the Department of Chemical Engineering at Imperial College London, estimates that the pipelines would contain between 150 and 300 million m3.
“It is unlikely that all of the contents will leak,” he estimated, but if just one of the pipes empties completely, it would match the worst leak ever recorded in the United States, in 2015, at the California underground storage site of Aliso Canyon.
Lauri Myllyvirta, an analyst at the Center for Energy and Clean Air Research, estimates that between 180,000 and 270,000 tons could be released, depending on the pressure in the pipelines. While this is a significant amount, it represents only about 1% of annual methane emissions from the hydrocarbon sector in Russia, estimated at 18 million tons in 2021 by the International Energy Agency (IEA).
And compared to global emissions?
The IEA has often pointed to the huge amounts of methane that leak out of fossil fuel production facilities around the world each year.
By 2021, it had estimated that these global leakages were equivalent to the entire gas consumption of the energy sector in Europe. As for the world’s gas infrastructures, which are often poorly maintained, they lose about 10% of the quantities transported due to leaks.
Leakage from Nord Stream will have “an immediate warming effect locally and on air quality,” says Piers Forster, director of the Priestley International Climate Centre at the University of Leeds, UK.
But on a global level, they don’t amount to much, the equivalent of about two and a half hours of programming,” says Jeffrey Kargel. However, according to him, they are a reminder of the urgency of the fight against these emissions, while the disastrous impacts of global warming are increasingly felt around the world.
“The world’s climate is changing dramatically, with extreme climate impacts increasing every year,” he points out.
