In a paper published in Science Bulletin, scientists from the Institute of Tibetan Plateau Research, Chinese Academy of Sciences used a regional atmospheric inversion framework of the GONGGA (Global ObservatioN-based system for monitoring Greenhouse GAses) system to design an observation network that could minimize uncertainties in the top-down estimate of China’s land carbon sink. The uncertainty can be reduced from 1 Pg Ca^-1 to approximately 0.2 Pg Ca^-1 when 60 stations were implemented. Such an observation network will be a critical component in the future integrated observing system for monitoring China’s land carbon fluxes.

Accurate estimates of the size and distribution of China’s land carbon sink are essential to assess the current sink capability and to project the sink potential in the long term, providing scientific support for the achievement of its “carbon neutrality” target. The atmospheric inversion is an effective approach to quantify CO₂ fluxes, but current estimates of China’s land carbon sink from atmospheric inversion have large uncertainties, mainly limited by the sparsity CO₂ observation stations.

To expand the current observation network for accurately inferring China’s land carbon sink, scientists from the Institute of Tibetan Plateau Research, Chinese Academy of Sciences developed a regional atmospheric inversion framework within the GONGGA (Global ObservatioN-based system for monitoring Greenhouse GAses) system and proposed a ground-based observation network, published online in Science Bulletin on July 11^st.

The ground-based observation network was optimally designed to minimize uncertainties in inverted estimate of China’s land carbon sink. The proposed stations are mostly distributed over areas with high biosphere productivity during the growing season, such as Southeast China, Northeast China, North China and the Tibetan Plateau. Compared with the large spread of prior estimates of about 1 petagrams of carbon per year (Pg Ca^-1), the uncertainty is constrained within 0.3 Pg Ca^-1 when a total of 30 stations were deployed, and is further reduced to approximately 0.2 Pg Ca^-1 when 60 stations were deployed.

The proposed stations can cover areas where existing satellites have limited coverage due to cloud shadowing in the monsoon season or over complex topography. Such ground-based observation network will be a critical component in the future integrated observing system for monitoring China’s land carbon fluxes.