The article "Progress and Challenges in Remotely Sensed Terrestrial Carbon Fluxes" by Tao Wang et al. reviews the advancements and challenges in using remote sensing techniques to estimate terrestrial carbon fluxes. The authors synthesize satellite-based data and methodologies to evaluate the main components of terrestrial carbon balance, including gross primary production (GPP), net primary production (NPP), net ecosystem productivity (NEP), and net biome productivity (NBP). They highlight that global GPP during 2001-2022 is estimated at 134 ± 14 PgC yr⁻¹, with nearly half occurring in tropical regions. The net carbon sink is estimated at 2.28 ± 1.12 PgC yr⁻¹, comparable to stock change-based estimates but twice as large as model-based estimates. The study also decomposes satellite-derived net carbon balance to infer that ~43% of global GPP is respired through soil microbes, higher than previous bottom-up estimates. The authors discuss the principles of satellite-based retrieval of terrestrial carbon fluxes, including methods for estimating GPP, NPP, and NEP, as well as the impact of disturbances such as land-use changes and wildfires. They emphasize the importance of integrating multi-source satellite sensors and improving the representation of photosynthetic responses to rising CO₂ and disturbances. The review also addresses the uncertainties and challenges in satellite-based inversions, such as the impact of extreme events on land carbon fluxes and the need for more accurate atmospheric transport models. Key questions identified include how to improve the detection of long-term changes in GPP by incorporating physiological effects and whether satellite data can help determine if climate change has led to enhanced tree mortality. The study concludes by highlighting the need for further research to address these knowledge gaps and improve the accuracy of remotely sensed terrestrial carbon flux estimates.The article "Progress and Challenges in Remotely Sensed Terrestrial Carbon Fluxes" by Tao Wang et al. reviews the advancements and challenges in using remote sensing techniques to estimate terrestrial carbon fluxes. The authors synthesize satellite-based data and methodologies to evaluate the main components of terrestrial carbon balance, including gross primary production (GPP), net primary production (NPP), net ecosystem productivity (NEP), and net biome productivity (NBP). They highlight that global GPP during 2001-2022 is estimated at 134 ± 14 PgC yr⁻¹, with nearly half occurring in tropical regions. The net carbon sink is estimated at 2.28 ± 1.12 PgC yr⁻¹, comparable to stock change-based estimates but twice as large as model-based estimates. The study also decomposes satellite-derived net carbon balance to infer that ~43% of global GPP is respired through soil microbes, higher than previous bottom-up estimates. The authors discuss the principles of satellite-based retrieval of terrestrial carbon fluxes, including methods for estimating GPP, NPP, and NEP, as well as the impact of disturbances such as land-use changes and wildfires. They emphasize the importance of integrating multi-source satellite sensors and improving the representation of photosynthetic responses to rising CO₂ and disturbances. The review also addresses the uncertainties and challenges in satellite-based inversions, such as the impact of extreme events on land carbon fluxes and the need for more accurate atmospheric transport models. Key questions identified include how to improve the detection of long-term changes in GPP by incorporating physiological effects and whether satellite data can help determine if climate change has led to enhanced tree mortality. The study concludes by highlighting the need for further research to address these knowledge gaps and improve the accuracy of remotely sensed terrestrial carbon flux estimates.