Dr. Ray Nassar, Research Scientist, Department of Physics, University of Toronto.
The central objective of the United Nations' Paris Agreement is to limit Earth's warming to well below 2 C above pre-industrial levels, but preferably 1.5 C. This challenging task will require policies and tools to enable every sector of society to drastically reduce greenhouse gas (GHG) emissions to eventually reach net-zero.
Enacting the most effective and efficient strategies to reduce emissions starts with knowing in detail where, when and how much of these greenhouse gases we are emitting on Earth, followed by implementing emission reduction policies and tracking our progress.
Is it possible to track carbon dioxide (CO2) emissions and emission reductions from space? New research from my group shows that it is.
Why CO2 matters
According to the Environmental Protection Agency, CO2 is the primary greenhouse gas driving climate change. Burning fossil fuels for electricity generation, heating buildings, industry and transportation has elevated the CO2 in Earth's atmosphere well beyond natural levels.
Currently, CO2 emission reporting is mainly done by accounting for the mass of fossil fuels purchased and used, then calculating the expected emissions — not actual atmospheric CO2 measurements. The finer details about exactly when and where the emissions occurred are often not available, but more transparent monitoring of CO2 emissions could help track the effectiveness of policies to reduce emissions.
Today GPS satellites help us to get around, meteorological satellites track weather systems and communication satellites relay TV, internet and telephone signals. It is time we use satellites to help tackle the biggest challenge that humanity has ever faced — climate change.
Satellites for measuring CO2
A global network of ground-based CO2 measurements began in 1957 and now consists of over one hundred stations around the world. Accurate and precise measurements from these stations have revealed a lot about changes in global atmospheric CO2 and Earth's overall carbon cycle, but we can’t place these stations everywhere on Earth.
Satellites can observe the entire planet. Those that measure CO2 in the lower atmosphere near Earth's surface (where CO2 emissions and CO2 uptake by plants happens) first began making measurements in 2002. Since then, they have been getting better and better at doing it, but there have been setbacks along the way.
About a decade of effort by NASA went into developing the Orbiting Carbon Observatory (OCO) satellite to make precise measurements of atmospheric CO2 across the Earth.
In 2009, OCO was lost due to a launch problem. After sustained advocacy for a rebuild of this important climate mission, NASA secured new funding to launch the OCO-2 satellite in 2014 and OCO-3 to the International Space Station in 2019.
The OCO missions were designed to improve our understanding of vegetation’s CO2 absorption, also known as the land carbon sink. But what about fossil fuel CO2 emissions?
A new way to verify CO2 emissions
In 2017, I led a research team that published the first study showing that we can quantify CO2 emissions at the scale of an individual power plant using OCO-2 observations.
Since OCO-2 was not designed for this purpose, its coverage and infrequent visits were inadequate for operational global CO2 emission monitoring, but we can still quantify emissions in select cases when the satellite passes close enough and gets a good cloud-free view.
OCO-3 is very similar to OCO-2, but has an additional pointing mirror that enables it to better map CO2 around targets of interest like the Bełchatów Power Station in Poland, Europe’s largest fossil fuel burning power plant and CO2 source.
With ten clear views of CO2 emission plumes from Bełchatów imaged by OCO-2 and OCO-3 from 2017-2022 analyzed in our new study, we were able to determine emissions on those days.
European power plants report hourly power generation but only annual CO2 emissions. Power generation fluctuates with electricity demand and generating unit shutdowns (for maintenance or decommissioning) and CO2 emissions are expected to exhibit proportional fluctuations.
We confirmed this using OCO-2 and OCO-3 in our recent paper, which showed that satellite observations can track changes in facility-level CO2 emissions. This means that satellites can be used to verify (or refute) reported CO2 emission reductions that result from climate change mitigation — like mandated efficiency improvements, carbon capture and storage technology, etc.
Emissions monitoring for the Paris Agreement
Our approach can be applied to more power plants or modified for CO2 emissions from cities or countries with OCO-2 and OCO-3. We can also try integrating the satellite observations with CO2 monitoring from the ground or aircraft.
While we are already working on this, advances will only be incremental until the launch of the European Commission-funded Copernicus Anthropogenic CO2 Monitoring Mission or "CO2M". CO2M is comprised of two satellites, aiming to launch in late 2025.
These satellites will provide about 50 times as much coverage as OCO-2 and OCO-3 combined and will form the space component of Europe's system for CO2 emissions Monitoring, Verification and Support (MVS).
CO2M will be a major advance, but just like successful global climate action, requires contributions from many countries. The long-term robust operational global monitoring of GHG emissions will need a constellation of satellites contributed by multiple countries as part of an integrated global observing system.
Hopefully, with new, more detailed and transparent tracking of human-caused greenhouse gas emissions to assess and guide us toward the most effective policies, society can achieve the emission reductions needed to reach net-zero in time.
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