The NASA measures carbon dioxide emissions

NASA's OCO-2 satellite measures global carbon dioxide emissions and removals, the greenhouse gas that impacts global climate
This map shows the average net emissions and removals of carbon dioxide from 2015 to 2020. The estimates are based on measurements from NASA’s OCO-2 satellite. Countries where more carbon dioxide was removed than emitted appear as green depressions, while countries with higher emissions are light brown or red and appear to stand out from the page. Credit: NASA

A NASA satellite, developed for Earth observation, has measured carbon dioxide emissions in over 100 countries worldwide. The project provides a new and powerful insight into the global emissions of this greenhouse gas. At the same time, it also reveals how much of it is being removed from the atmosphere by forests and other carbon absorption “sinks” within their borders. The results demonstrate how space-based instruments can support Earth insights as nations work towards climate goals.

Data in time for the Global Stocktake

The international study (ref.), conducted by over 60 researchers, used measurements from the Orbiting Carbon Observatory-2 (OCO-2) mission. Combined with a network of surface observations, increases and decreases in carbon dioxide from 2015 to 2020 were quantified. By using this approach, researchers were able to deduce the balance of how much carbon dioxide was emitted and removed.

While the OCO-2 satellite is not designed to estimate emissions for individual nations, the results from over 100 countries come at the opportune time. The first Global Stocktake summit, to assess the world’s collective progress towards limiting global warming as specified in the 2015 Paris Agreement, will take place in 2023.

“NASA focuses on providing scientific data about Earth to address the real-world climate challenges. These will help governments worldwide measure the impact of their carbon mitigation efforts” said Karen St. Germain, Director of NASA’s Earth Science Division. “This is an example of how NASA is developing and enhancing efforts to measure carbon dioxide emissions to meet user needs”.

Classic estimates vs. modern estimates

Traditional approaches to carbon measurement rely on counting and estimating the amount of carbon dioxide emitted in all economic sectors, such as transportation and agriculture. These “bottom-up” analyses are essential, but their compilation requires significant economic resources, expertise, and knowledge.

For these reasons, developing an emissions and removals database through a “top-down” inverse approach could be particularly useful for nations with limited resources. In fact, the scientists’ findings include data for over 50 countries that have not reported emissions to the global community in the past decade.

The study also provides a new perspective compared to traditional methods. It monitors both fossil fuel emissions and changes in the total carbon “stock” in ecosystems, including trees, shrubs, and soil. The data is particularly useful for tracking carbon dioxide fluctuations related to land cover change. However, the authors have stated that bottom-up methods remain essential. Nevertheless, these methods are vulnerable to uncertainty when data is missing or the net effects of specific activities are unclear.

“Our top-down estimates provide an independent estimate of these emissions and removals. While they do not replace the bottom-up methods, we can verify the consistency of both approaches” said Philippe Ciais, an author of the study.

Carbon monitoring

The study offers a complex picture of carbon moving through the planet’s land, ocean, and atmosphere. In addition to direct human impacts, pristine ecosystems like certain tropical and boreal forests can sequester carbon from the atmosphere, thus reducing the potential for global warming.

“National inventories aim to track the impact of management policies on CO2 emissions and removals,” said study author Noel Cressie, a professor at the University of Wollongong in Australia. “However, the atmosphere doesn’t care whether CO2 is emitted from deforestation in the Amazon or fires in the Canadian Arctic. Both processes will increase atmospheric CO2 concentration and drive climate change. Therefore, it is crucial to monitor the carbon balance of unmanaged ecosystems and identify any changes in carbon uptake.”

Looking to the future, the researchers have stated that their pilot project can be further refined to understand how emissions are changing for individual nations. “Sustained, high-quality observations are critical for these top-down estimates” said lead author Brendan Byrne, a scientist at NASA’s Jet Propulsion Laboratory. “Continued observations from NASA and surface sites will allow us to monitor how these emissions and carbon dioxide removals are changing. Future international missions will provide extensive mapping of global CO2 concentrations and allow us to refine these estimates.”

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