As the world works toward a clearer picture of where carbon is emitted and absorbed, satellites are becoming increasingly important tools for tracking the global carbon cycle. China is preparing to launch its next-generation carbon monitoring satellite, TanSat-2, which is designed to provide global and regional observations of column-averaged carbon dioxide (CO2) and methane (CH4).
One of the major challenges in satellite-based carbon monitoring is distinguishing CO 2 released by human activities from the carbon exchanged between the atmosphere and terrestrial ecosystems. Atmospheric CO 2 observations contain signals from both processes, making it difficult to determine how much of the observed CO 2 originates from fossil fuel emissions and how much is associated with ecosystem carbon uptake and release.
A recent collaborative study by Chinese and UK researchers published in Advances in Atmospheric Sciences explores how TanSat-2 could help address this challenge.
This study introduces a newly developed carbon flux inversion approach that combines atmospheric CO 2 measurements with solar-induced chlorophyll fluorescence (SIF), an observational proxy closely related to vegetation photosynthetic activity. By bringing these two complementary measurements together, the approach can simultaneously constrain net primary productivity (NPP) and fossil fuel combustion emissions (FF).
To further improve the separation of natural ecosystem carbon fluxes and fossil fuel emissions, the researchers applied empirical orthogonal function (EOF) analysis to prior NPP and FF inventories. This identifies their dominant spatial and temporal patterns while reducing the number of variables that need to be optimized in the inversion.
The researchers then put the proposed TanSat-2 observing strategy through a virtual test using Observing System Simulation Experiments (OSSEs). Under idealized conditions in which observational biases are effectively controlled, the results show that TanSat-2 CO₂ and SIF observations could lead to an NPP error reduction of up to 95% over Siberia and the Amazon, and to error reductions of about 80% for FF emissions in regions including Siberia, northern Asia, the United States, and South Africa.
The study, however, also highlights an important challenge. Even small systematic biases in satellite-derived column-averaged dry-air mole fractions of CO 2 (XCO 2 ) can substantially distort inferred CO 2 sources and sinks—or even lead to their misattribution. Such biases could ultimately compromise the reliability of carbon flux estimates, underscoring the importance of carefully identifying and correcting systematic errors in satellite retrievals and subsequent data applications.
The researchers also investigated whether increasing TanSat-2’s cross-track swath width could strengthen its carbon-monitoring capability. Their results indicate that a wider observational swath can improve the robustness of CO 2 flux estimates. The study further develops an error-matrix analysis framework that could help evaluate observing strategies and support the design and optimization of future carbon-monitoring satellite missions.
“Reliable monitoring of carbon fluxes at both global and regional scales cannot rely on satellites alone.” The lead author, Dr. YANG Dongxu from the Institute of Atmospheric Physics at the Chinese Academy of Sciences concluded their study and emphasized, “Instead, it requires the integration of satellite, ground-based, airborne, and in situ observations. Together, these complementary observing systems will be essential for building a more accurate and comprehensive picture of Earth’s carbon sources and sinks.”
A step forward to global segment CO2 flux estimation benefiting from large swath of coordinated CO2 and SIF measurement from TanSat‑2 mission
2-Sep-2026