North Sea Gas Leak: Experts Assess Climate Impact of Ongoing Accident

The infrared camera image taken by Greenpeace shows the
scale of the gas cloud from energy giant Total's Elgin platform.

The French energy company Total estimates that its North Sea Elgin field gas well is leaking about 200,000 cubic meters of natural gas per day, enough, according to the U.S. Energy Information Agency, to supply more than 100 average homes with natural gas for an entire year. Total estimates that it may take six months to stop the leak.

If the gas continues escaping at that rate, and all of it reaches the atmosphere, it would approximate the annual global warming impact of 35,000 Americans, says Carnegie Institution for Science Department of Global Ecology director, Christopher Field.

At a news conference on Monday, Total’s chief financial officer, Patrick de la Chevardiere, said that because the leak involves natural gas, which disperses into the atmosphere very quickly, and not crude oil, “the current impact on and risks for the environment are relatively low.” But climate scientists and biologists say the leak’s impact shouldn’t be dismissed just because it isn’t creating a beach- and wildlife-fouling oil slick.

The leak, detected March 25th, is at the wellhead platform of Total’s G4 well, located approximately 150 miles east of Aberdeen, Scotland. The gas is mostly methane, which is considered the second largest contributor to human-caused global warming after carbon dioxide.

The gas is believed to be coming from a rock formation almost 2.5 miles below the seabed and almost 2/3rds of a mile above the well’s main gas reservoir. The gas, however, is leaking at the platform level, rather than deep underwater. The well was plugged in February 2011 and wasn’t in production when irregular pressure was observed at the wellhead last month. Total was pumping in high-density mud to strengthen the seal when a sudden pressure increase apparently triggered the leak.

Compared to CO2, which remains in the atmosphere for hundreds of years, methane is relatively short-lived, with an atmospheric lifetime of approximately 12 years. But methane’s global warming potential is much greater than CO2’s. Scientists often make this comparison using a 100-year time scale, on which methane’s global warming potential is 25 to 33 times that of CO2. Were the Elgin well to continue leaking at its current rate for six months, Field said it would release nearly 26,000 tons of methane and have the global warming potential of 175,000 tons of carbon—equal to the average 2010 carbon footprint of 35,000 Americans.

Cornell University Professor of Ecology and Environmental Biology Robert Howarth, who has been analyzing methane emissions for the federal government’s National Climate Assessment, says the latest scientific data shows an urgent need to get methane emissions under control. If action isn’t taken in the next 15 to 35 years, said Howarth, we risk reaching “potentially dangerous tipping points in the climate systems.” Given this urgency, he said, it makes sense to compare methane and carbon dioxide on a 20-year time frame rather than the 100-year scale. Calculations using that shorter time-scale show that methane is 105 times greater than CO2 in its global warming potential, he said.

Howarth calculates that if the Elgin well leaks at its current rate for six months it would release some “25 billion grams of methane, equivalent to 2.6 trillion grams of CO2 in terms of global warming.”(Huffingtonpost.com)