Nord Stream methane leak larger than initial estimates

Nord Stream methane leak larger than initial estimates
by Erica Marchand
Paris, France (SPX) Mar 11, 2025

A new study published in *Nature* reveals that the methane released from the Nord Stream gas pipelines in 2022 was more than twice the initially estimated volume. The leak, one of the largest human-related methane emissions events recorded, occurred in late September 2022 when both Nord Stream pipelines were damaged.

According to the study, methane emissions from the rupture ranged between 445,000 and 485,000 tonnes, significantly higher than earlier estimates, which suggested a range of 75,000 to 230,000 tonnes. The study was coordinated by the United Nations Environment Programme (UNEP).

Satellite data and research methods

To assess the scale of the leak, researchers analyzed data from multiple satellite missions, including Copernicus Sentinel-1 and Sentinel-2, along with the Infrared Atmospheric Sounding Interferometer (IASI) on Eumetsat's MetOp-B satellite. Additional data from third-party satellite missions, such as Landsat 8 and GHGSat, were incorporated. Ground-based and aerial observations, marine data, and engineering assessments further contributed to the comprehensive evaluation.

The study cross-referenced these datasets with pipeline emission models to generate a precise estimate. Stephen Harris, a scientist at UNEP's International Methane Emissions Observatory (IMEO), explained, "Satellite observations were just one component of a broader set of measurement approaches, which together enabled the study to provide a comprehensive and accurate assessment of methane emissions from the event - highlighting the importance of integrating diverse, complementary methane measurement methods."

Seventy researchers from 30 institutions collaborated on the study, which received partial funding from two ESA Earth Observation Science for Society initiatives: MethaneCamp and Methane+. Edward Malina, an ESA Earth Observation Atmosphere Scientist, emphasized, "This study shows the benefits and importance of methane concentrations provided by satellites on a regular basis."

Diego Fernandez Prieto, Head of ESA's Earth Observation Science Section, remarked, "Sustained ESA support to scientific advances on methane measurements from satellites have improved our ability to characterise methane leaks globally. I believe this is a good example of how science is transferred into climate action as we are now better equipped to monitor progress and respond to the Global Methane Pledge."

The study was coordinated by IMEO, a key implementing partner of the Global Methane Pledge.

Impact compared to other methane leaks

The new upper estimate for the Nord Stream leak far surpasses the previous largest methane leak on record-an estimated 109,000 tonnes released from the Aliso Canyon Natural Gas Facility in the U.S. between October 2015 and February 2016. Despite the magnitude of the Nord Stream event, Harris pointed out that it accounted for just 0.1% of global human-caused methane emissions in 2022.

"This is equivalent to only two days of the oil and gas industry's annual methane emissions. This highlights the vast number of other human-caused methane sources that still require global mitigation efforts," Harris noted.

According to the International Energy Agency, fossil fuel production and usage accounted for nearly 120 million tonnes of methane emissions in 2023, with an additional 10 million tonnes from bioenergy. Global methane emissions have remained steady since peaking in 2019.

Clarifying the revised estimates

Uncertainty surrounded the true impact of the Nord Stream leaks until this latest study, which provides the first comprehensive assessment. The significant increase in estimated emissions is attributed to the incorporation of more complete datasets and improved measurement techniques. Initial estimates were based on limited and sometimes incomplete data, leading to widely varying figures.

Stephen Harris explained, "These estimates varied widely, each capturing only part of the story from a different perspective. This study presents the first updated estimate that incorporates all available data to account for every aspect of the emission event: the methane present in the pipeline before and after the ruptures, the amount dissolved in the Baltic Sea, and the portion ultimately released into the atmosphere. Satellite-based measurements played a crucial role in understanding the latter."