Recent increasing trend of global CO2 growth rate due to a slowdown in terrestrial carbon uptake

The global atmospheric CO₂ growth rate is a product of the combined effects of emissions and uptake from both anthropogenic and natural carbon sources. Therefore, an evaluation of the global CO₂ growth rate should be preceded to understand the global carbon-climate process. In this study, we analyzed the long-term changes in the global CO₂ growth rate from 1991 to 2020, using data from 42 global sites and model simulations to assess recent changes in the global carbon-climate feedback process. Our results indicate that the annual CO₂ growth rate has increased by 0.032 ppm yr^-2 since the 2000s. A comprehensive assessment of carbon cycle components contributing to atmospheric CO₂ growth rate changes reveals that the strengthening of this rate is linked to a decline in terrestrial carbon absorption over the last decade. This decline is primarily associated with a slowdown in the increasing trend of Net Primary Productivity. Consequently, the reduced terrestrial carbon uptake in recent decades contributed to an approximately 3 ppm increase in global CO₂ concentration by 2020. Our findings highlight that the vegetation's carbon uptake capacity can no longer offset anthropogenic CO₂ emissions, underscoring the importance of achieving global carbon neutrality in climate change mitigation.

 

This work was supported by Korea Environment Industry & Technology Institute(KEITI) through Project for developing an observation-based GHG emissions geospatial information map, funded by Korea Ministry of Environment(MOE) (RS-2023-00232066)