Nord Stream: Russian gas pipe leaks could have an 'unprecedented' environmental impact

Unexplained leaks in two Russian gas pipelines in the Baltic Sea are spewing out greenhouse gas emissions.

It is feared that the disruption could cause a climate calamity - although to what extent is still unclear.

Neither pipeline was in operation, but both contained natural gas. This is largely composed of methane, a potent greenhouse gas that is the second biggest cause of climate change after CO2.

"There are a number of uncertainties, but if these pipelines fail, the impact to the climate will be disastrous and could even be unprecedented," says atmospheric chemist David McCabe, senior scientist at the non-profit Clean Air Task Force.

Over a 20-year timeframe, methane has more than 80 times the planet-warming potency of carbon dioxide, and roughly 30 times its potency over 100 years. Scientists say sharp cuts in methane emissions over the next few years will be a vital lever in curbing climate change.

McCabe and other emissions experts say it is not yet possible to assess the size of the leak. This is due to uncertainties around factors such as the temperature of the gas in the pipeline, how fast it is leaking, and how much gas would be absorbed by microbes in the water before reaching the surface.

But since both Nord Stream pipelines contained mostly methane, "the potential for a massive and highly damaging emission event is very worrisome", says McCabe.

Jasmin Cooper, a research associate at Imperial College London's Sustainable Gas Institute, agrees it will be difficult to quantify exactly how much gas is reaching the atmosphere - especially given scarce existing data on leaks from subsea pipelines.

"Gazprom will probably have an estimate based on gas throughputs, but in terms of how much gas/methane is emitted into the