The Chinese Academy of Sciences released a report on remote sensing assessment of global carbon emission and carbon budget at a seminar held in Beijing on July 26, 2023, and provided important scientific data for China's response to carbon inventory, and carbon neutrality. 

The report, Remote Sensing Assessment Report on Global Carbon Emission and Carbon Budget was led by researchers from the Aerospace Information Research Institute (AIR) under the Chinese Academy of Sciences (CAS), together with several other institutions and universities. 

Carbon Dioxide (CO₂), the primary component of greenhouse gases that trap the heat in the Earth's atmosphere is regarded as one of the culprits of global warming. However, human activities have been emitting extra greenhouse gases including CO₂ into the atmosphere since the industrial revolution. 

Satellite measurement offers a powerful top-down approach to estimate global carbon emissions and how much of it is removed from the atmosphere by forests and other carbon sinks, therefore providing insights on the Earth as individual countries work to achieve climate goals.  

The report used satellite remote sensing, big data, and other technologies to monitor the temporal and spatial changes in carbon dioxide concentrations and quantified the impact of human activities and ecosystems on atmospheric carbon dioxide concentrations. 

The report covers 11 related themes around three fields with the greatest uncertainties in carbon emission and removal, meaning, the fossil fuels and industrial emissions, land use emissions, and carbon sequestration of terrestrial ecosystems. 

Over the past decade, the global atmospheric carbon dioxide concentration has continued to rise at an average annual growth rate of 6 ‰, and global greenhouse gas emissions have not been effectively controlled, according to the report. The increase of global CO₂ concentration has not significantly reduced even during the period of COVID-19. 

The report showed that accelerated deforestation has not been curbed over the past four decades, and forest area has been continuously reduced. The global land use change has produced an average annual emission of about 3.2 billion tons of carbon dioxide, which is the second largest emission source after fossil fuel carbon emissions. 

Meanwhile, thanks to its large-scale afforestation and ecological engineering efforts, China has sequestered an average of nearly 400 million tons of carbon dioxide per year through carbon sinks, effectively reducing global land-use carbon emission during this period. 

The carbon absorption capacity, that is, the long-term storage of carbon in plants, soils and geologic formation, of global terrestrial ecosystems continues to increase, the report said. It showed that global terrestrial ecosystems absorbed an average 13.7 billion tons of CO₂ per year over the past decade, of which China's terrestrial ecosystems absorbed about 10 percent of the global total.  

Over the past 40 years, soil absorbed an average of about 1.3 billion tons of CO₂ per year globally, of which China's soil carbon sequestration rate was the highest, accounting for about one-quarter of the global total due to the country’s implementation of large-scale agriculture conservation and ecological management measures, according to the report.  

The report also showed that Chinese carbon satellites can not only achieve high-precision observation of global atmospheric CO₂ concentrations, but also demonstrate its capability in monitoring net carbon fluxes, that is, the net exchange of carbon dioxide between land and atmosphere. 

The accuracy of global net carbon flux estimation has been significantly improved with optimized calculation by Chinese carbon satellites. The annual net carbon flux estimation margin of error has been reduced from 4.3 billion tons of CO2 to 470 million tons, according to the report. 

China will launch a next-generation carbon satellite in 2025 to monitor global atmospheric CO₂ concentrations with higher precision and efficiency, according to Prof. WU Yirong, director-general of AIR. 

AIR will continue to cooperate with other domestic researchers to boost the capacity of global carbon stock and verification method based on domestic satellite observation data, according to Prof. LIU Liangyun from AIR, a leading author of the report, “to further help reduce the uncertainties of global and national carbon budget and provide continuous scientific data for China's carbon neutrality goal”. 

The report is supported by national key R&D project and will be updated and published annually.