Neither of the two breached Nord Stream pipelines, which run between Russia and Germany, was operational, but both contained natural gas. This mostly consists of methane — a greenhouse gas that is the biggest cause of climate heating after carbon dioxide.
The extent of the leaks is still unclear but rough estimates by scientists, based on the volume of gas reportedly in one of the pipelines, vary between 110,231 and 385,808 tons (100,000 and 350,000 metric tons) of methane.
Jasmin Cooper, a research associate at Imperial College London's department of chemical engineering, says a "lot of uncertainty" surrounded the leak.
"We know there are three explosions, but we don't know if there are three holes in the sides of the pipe or how big the breaks are," Cooper says. "It's difficult to know how much is reaching the surface. But it is potentially hundreds of thousands of metric tons of methane: quite a big volume being pumped into the atmosphere."
Nord Stream 2, which was intended to increase the flow of gas from Russia to Germany, reportedly contained 10.5 billion cubic feet (300 million cubic meters) of gas when Berlin halted the certification process shortly before Russia invaded Ukraine.