The natural gas from the Nord Stream pipelines is almost 100 percent methane
Significant amounts of methane have escaped from the gas leaks in Nord Stream 1 and Nord Stream 2.
The exact amount is not yet known.
However, an evaluation by the Integrated Carbon Observation System (ICOS) now shows how a huge gas cloud rose over the Baltic Sea and moved over Europe.
Methane measuring stations in Sweden, Norway and Finland have shown clear swings in the past few days.
Observation satellites probably would not have recorded the emissions because it was cloudy, ICOS writes in a statement.
The network records standardized emissions across Europe.
"We assume that the wind first carried the methane north to the Finnish archipelago and then turned towards Sweden and Norway," says Stephen Platt from the Norwegian Institute for Air Research (NILU).
It shows an animation that the experts created based on their evaluations (see above).
First Nord Stream 2, then Nord Stream 1
A graphic of the measured values shows the first clearly recognizable increase in methane values in the night from Monday to Tuesday at a station on the island of Utö off the south coast of Finland.
On Tuesday, the methane cloud then massively increased the statistics at the Norunda research station north of the Swedish city of Uppsala.
The methane content of the air there rose within a few hours from a good 2000 to more than 2300 ppb (parts per trillion), i.e. particles per billion air particles.
On the same day, the measured values from the stations further west Hyltemossa in Sweden and Birkens in Norway were similarly strong.
Methane is a greenhouse gas about 25 times more potent than carbon dioxide (CO2).
There is a short break in all three series of measurements, the values drop briefly and then rise again.
At first glance, this fits with the course of the damage to the pipelines.
Nord Stream 2 was the first to leak on Monday night, and then the pressure in Nord Stream 1 fell rapidly on Monday evening.
However, this does not explain the pattern in the series of measurements.
"That's because the air in the atmosphere acts like a mixer and doesn't always flow directly from the methane source to the measuring station," explained ICOS director Werner Kutsch in an interview with SPIEGEL.
A total of four holes are now known, affecting three tubes of the two pipelines.
The question of the amount of methane
At a later date, the ICOS network will try to quantify the amount of gas that escaped more precisely.
"We see the advantage of a standardized, large network in cases like this, where we can quickly and reliably detect unexpected increases or decreases in greenhouse gases," says Kutsch.
So far, there are only estimates of the amount of gas that has escaped into the atmosphere: "The leaks could have released as much gas as a city of Paris or a country like Denmark in a whole year," says the ICOS statement.
The Federal Environment Agency estimates that around 7.5 million tonnes of CO₂ equivalents were emitted.
This corresponds to about one percent of Germany's total annual emissions.
"That's a considerable amount of greenhouse gas that can be emitted there," Gregor Rehder from the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) told SPIEGEL on Thursday (read more about it here).