An international team of researchers has recently used a NASA satellite – the Orbiting Carbon Observatory-2 (OCO-2) – to track carbon dioxide emissions for over 100 countries across the world, as well as to clarify how much of this gas is removed from the atmosphere by forests and other carbon sinks. The analysis revealed that the world’s largest CO2 emitters are China and the United States, followed by India, Indonesia, Malaysia, Brazil, Mexico, Iran, Japan, and Germany.
Other nations that significantly contribute to CO2 emissions are the United Kingdom – along with the rest of western Europe – Australia, Kazakhstan, most of northern Africa, South Africa, Chile, Thailand, and the Philippines.
While traditional activity-based (“bottom-up”) approaches to carbon measurement rely on tallying and estimating how much CO2 is emitted across all sectors of the economy, the current “top-down” approach is particularly helpful for countries that lack traditional resources for inventory development. By tracking both fossil fuel emissions and the total carbon stock changes in ecosystems – including soils, trees, or shrubs – such an approach is highly useful for clarifying CO2 fluctuations related to land cover change.
“Our top-down estimates provide an independent estimate of these emissions and removals, so although they cannot replace the detailed process understanding of traditional bottom-up methods, we can check both approaches for consistency,” said study co-author Philippe Ciais, the research director at the Laboratory of Climate and Environmental Sciences in France.
Such an approach provides a highly complex picture of how carbon dioxide is moving through out planet’s land, ocean, and atmosphere. Moreover, besides measuring direct human impacts already accounted for by national inventories, it also helps monitoring the carbon balance of unmanaged ecosystems, such as tropical or boreal forests that can sequester carbon from the atmosphere and thus help mitigate global warming.
“Sustained, high-quality observations are critical for these top-down estimates,” explained lead author Brendan Byrne, a scientist at NASA’s Jet Propulsion Laboratory in Southern California. “Continued observations from OCO-2 and surface sites will allow us to track how these emissions and removals change as the Paris Agreement is implemented. Future international missions that provide expanded mapping of CO2 concentrations across the globe will allow us to refine these top-down estimates and give more precise estimates of countries’ emissions and removals.”
The full study can be found here.
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