“Worth targeting?”
The date is September 26th, 2022, and I just received an email with those two words from Stephane Germain, GHGSat’s CEO, along with a link to a BBC article: Russia’s gas pipeline leaking into Baltic Sea – Denmark.
The pipeline in question was 1200 km long, connecting Russia’s natural gas to Europe. It wasn’t operational, but it was full of natural gas—pressurized methane.
At GHGSat, we had been working on developing the ability to measure methane emissions from offshore areas. Why? Methane, an odorless and colorless gas, is the second-largest contributor to global warming, after carbon dioxide. When released into the atmosphere, it has 80 times the warming potential of CO2 over a 20-year period, making actions to cut methane emissions central for a relatively quick climate response.
At this point, GHGSAT’s satellites had been regularly detecting methane emissions from industrial facilities on land. The infrared sensors on the satellites work by analyzing signatures of the sun’s rays after they have bounced off the surface of the Earth and interacted with methane molecules in the atmosphere. However, measuring methane emissions over water from space is more difficult. Very little light at those wavelengths gets reflected off water, and, as a result, the methane signatures in the sun’s rays are much harder to discern. Anyone who’s ever tried low-light photography knows it can be challenging—now amplify those difficulties by doing this from a small satellite over 500 km away from the Earth and moving in constant orbit at 7 km/s.
Despite the challenges, we were determined. Offshore platforms generate over one-quarter of global oil and gas production. Without an understanding of offshore emissions, operators and governments are missing a big part of the emissions picture, as well as opportunities to mitigate them. It is critical to develop cost-effective technologies for detecting and quantifying offshore methane emissions globally.
In 2022, we had been working to overcome this limitation by looking at what is called the “glint spot.” If you have ever gone canoeing on a Canadian lake near sunrise or sunset, you’ve probably seen this effect before. When the sun approaches the horizon, there’s a large pool of light that gets reflected off the surface of the water. In technical terms, the sun’s rays undergo “specular reflection.” Like a mirror, much more light will bounce off the surface at this point—enough to scan for the presence of methane with GHGSAT’s infrared sensors. This approach, which is called “glint mode,” opens the door to satellite monitoring of emissions for thousands of remote offshore platforms across the globe.
So, back to the question at hand. Worth targeting? The pipeline is over 1200 km long, and the leak could have occurred anywhere along it. Even with a satellite that can take images 10–20 km wide, the sea is a big place. We needed to know where to look. Luckily, we managed to unearth a navigational warning from Danish authorities prohibiting ships from approaching an area with an observed gas leak. The incredible GHGSAT Operations team immediately started tasking all the satellites in our constellation to measure the methane leaking from the pipeline explosion into the atmosphere, using our new glint mode. We needed to carefully time the observation to line up the target between the satellite and the sun; otherwise, we wouldn’t be able to see anything.
On September 27, 2022, we got our first opportunity. Over the course of 20 seconds, the GHGSAT instrument took the measurement while the satellite passed over the leak. We then needed to wait for the satellite to pass over one of our ground stations before we could downlink the data to Earth.
The images came in. I loaded them onto my computer. Cloudy. The reality of space-based remote sensing is that we can’t detect leaks through clouds. Unfortunately, clouds were forecast for the next several days. Time was pressing as we didn’t know how long the leak would last. On September 30, however, reports came in that the weather in the Baltic Sea would clear up soon. This was our chance. We had three back-to-back opportunities to measure the leak.
The figure on the right-top corner shows plumes detected by GHGSat satellites from the Nord Stream leak on September 30th, 2022. (The color scale is 0-700 ppb for all three images, which also have identical spatial scales.)
Aha! Those three opportunities, spaced about two hours apart, each yield a large emission from the same location. So much gas was leaking from the pipeline that an area 500 meters across was covered in bubbles. Five days after the incident was first reported, the Nord Stream 2 pipeline was still spewing methane at a rate of 84,000 kg/h, making the emission one of the biggest single leaks we’ve ever seen since our first satellite was launched in 2016.
Over the next two years, I worked with a team led by the UN’s International Methane Emissions Observatory in their effort to quantify the total amount of methane that was released into the atmosphere. Initial estimates of the leak varied widely, ranging from 100,000 to 480,000 tons of methane. That was a huge level of variation. Without knowing the true amount of methane that was released, it would be difficult to assess the damage to the atmosphere.
Since our satellites took measurements of the leak, representing just a few snapshots in time, they were a critical part of the puzzle, but not the only one. We needed to acquire many images and data points from different sources to build a full picture of the leak over the full length of time that it was emitting. The international team had the difficult task of reconciling modelled atmospheric emissions with emission rates from different data sources, including meteorological towers, airplanes, and our own satellites. The verdict? The explosion released up to 485,000 metric tons of methane to the atmosphere over the course of a week—the largest recorded amount of methane released from a single transient event. For Montreal Canadiens fans out there, you could fill the entire Bell Centre hockey arena with the equivalent amount of liquified methane. And yet, it was equivalent to only 0.1% of methane emissions released by humans in 2022.
The world emits staggering amounts of methane. But drawing on technologies like satellites, we can better understand where that methane is coming from and quantify how much—a foundational first step towards addressing the impact of those emissions.
Read the full paper here: https://www.ghgsat.com/en/scientific-publications/methane-emissions-from-nord-stream-subsea-pipeline-leaks/
