Jacinta Bowler
Jacinta Bowler is a science journalist at Cosmos.
They were published in the Best Australian Science Writing 2023.
To ensure that countries keep their climate commitments, more needs to be done to rein in ‘super-emitters’ such as power plants, megacities, refineries, and giant factories. These together are responsible for nearly half of humanity’s total output of greenhouse gases.
Now, scientists have shown that for these large super-emitters of carbon dioxide ‘tracking-at-the-source’ is already possible, even with existing satellites.
A new study, published in Frontiers in Remote Sensing undertook a “proof-of-principle,” using five years of carbon dioxide measurements from NASA’s Orbiting Carbon Observatory 2 (OCO-2) and OCO-3 – which is attached to the ISS.
The researchers found that they were able to track the emissions from Europe’s largest fossil fuel power plant – the Bełchatόw Power Station in Poland – 10 times over 5 years. Each of those tracked emissions – called ‘top-down’ reporting – matched closely with what the power station estimates it had emitted at that time – known as ‘bottom up’ reporting.
“European power plants publicly report annual emissions and hourly power generation,” first author Ray Nassar, a senior researcher at Environment and Climate Change Canada, told Cosmos.
“When power generation is reported to have decreased (due to temporary or permanent unit shut-downs), the [satellites can] detect these changes.”
Read more: Are Australia’s coal companies underreporting their methane emissions?
This is great news for researchers, and bad news for big emitters, as in the next few years, the EU plans to launch its CO2M (Copernicus Anthropogenic CO2 Monitoring Mission) pair of satellites. They’ll have around 50 times as much observational coverage as OCO-2 and OCO-3 and will be able to monitor smaller sources of carbon dioxide emissions.
CO2 is emitted by the 300-metre-high stacks at Bełchatów and the invisible plume, anywhere from 10-50km long, is carried by the wind about 550 meters above Earth. OCO-2, which orbits the Earth at an altitude of 705 km, passes every 16 days, close by or directly over Bełchatów. OCO-3 orbits at a lower altitude and passes near Bełchatów more frequently.
Unfortunately, top-down reporting can’t get information every time. Satellites can assess the carbon dioxide emitted by a source only in the absence of clouds, and when the plume doesn’t pass over large water bodies or mountains. This means that the conditions have to be ideal to record the carbon dioxide levels.
Measuring extra carbon dioxide from a source is harder than for other gasses like nitrogen dioxide or methane because of its lack of reactivity.
“The more reactive a gas is, the easier it is to observe its enhancement above the background. If a gas is very reactive like nitrogen dioxide, it disappears quickly. Maps of a reactive gas like nitrogen dioxide easily show ‘hotspots’, where it is emitted,” says Nassar.
“Carbon dioxide is very unreactive, so it stays in the atmosphere long after being emitted – this is also a reason why it is such a problem for climate change. Earth’s entire atmosphere already has ~415 PPM of carbon dioxide, so emissions from a power plant only cause enhancements on the order of a few PPM, making it somewhat harder to detect and quantify. But (with Bełchatów ) we were working with a large/strong carbon dioxide source, which is easier.”
Another greenhouse gas also being emitted from fossil fuel – methane – is easier to monitor and more regular top-down reporting can be done. The UN has recently announced a worldwide satellite methane monitoring system.
“Top-down satellite emissions monitoring is just in its infancy,” says Nassar. “In the next 5 years, a flurry of new satellite missions will be launched that will be designed specifically for monitoring carbon dioxide, methane and other gases.
“Countries report economic indicators (unemployment rates, housing prices, inflation, etc.) monthly or better in some cases, in order to gauge the direction of the economy.
“Environment/climate data needs more frequent and detailed reporting, with shorter time lags to reflect its importance and guide decision-makers to help reduce emissions. Satellites can help to provide this information.”