Nov. 11 () –
Chinese researchers have calculated the impact on the climate of the methane leak from the Nord Stream gas pipelines and conclude that it has been insignificant, as published in ‘Advances in Atmospheric Sciences’.
On September 26, Nord Stream 1 and 2, two underwater pipelines to transfer natural gas from Russia to Germany, were deliberately ruptured and massive amounts of gases, mainly methane, they escaped into the ocean and were released into the atmosphere.
Methane is the second most abundant anthropogenic greenhouse gas after CO2, but it has a much stronger greenhouse effect. For this reason, the possibility of this incident having negative climatic effects is one of the main concerns throughout the world. In an article published in the magazine ‘Nature’ this question was commented, but no quantitative conclusions were drawn.
Now, researchers from the Institute of Atmospheric Physics of the Chinese Academy of Sciences have calculated that potential impact by adopting the energy conservation framework of the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR6), published in 2021.
After compiling all the estimates of the total amount of leaked methane available in the world media after the incident, it was found that the first estimates (1-2 days later) reached up to 0.5 million tons (Mt).
However, it later became clear that the amount of methane that leaked out was probably much less than originally estimated. Specifically, a team from Nanjing University, China, provided a more precise estimate of 0.22 +/- 0.03 Mt based on multiple observations, including those from high-resolution satellites.
This value established that it was the largest single-event methane emission in human history, more than double that of the Aliso Canyon accident in California in 2015. However, according to the IPCC AR6, annual emissions of methane from the oil and gas sectors amounted to up to 70 Mt during 2008-2017. The methane leak from the Nord Stream pipelines was equivalent to just one day of emissions from these sectors.
IPCC AR6 also highlighted that methane in the atmosphere is gradually removed by reacting with certain radicals, such as the hydroxyl radical, resulting in a lifespan of about 10 years, which is short-lived compared to CO2. This means that the climate impact of methane depends on the time horizon, which complicates things when trying to calculate it directly.
Instead, the researchers made an indirect estimate with the help of the “global warming potential” concept. Specifically, they determined that the amount of heat accumulated per unit mass of methane in the 20 years following its emission into the atmosphere is 82.5 times higher than that of CO2.
Then, with this information, they were able to calculate that, considering a time horizon of 20 years, the climate impact of filtered methane is equivalent to that of 20.6 Mt of CO2, which would raise the atmospheric concentration of CO2 by only 0.0026 ppm.
Based on the latest IPCC AR6 assessments of effective radiative forcing under double CO2, climate feedback, and ocean heat absorption efficiency, under energy conservation, the global mean air temperature on the surface it would theoretically increase by 1.8×10 raised to -5 degrees Celsius.
“Such tiny warming cannot be perceived in ecosystems or in human society,” explains doctor Xiaolong Chen, first author of the study.
“Still, anthropogenic methane has been the second biggest driver of global warming, and it’s emitted from multiple sectors of agriculture and industry,” he adds. “If we want to hit the below 1.5 or 2 degrees Celsius established in the Paris Agreement, Damage to infrastructure like this needs to be avoided in order to better control and reduce methane emissions.”
