Emerging climate impact on carbon sinks in a consolidated carbon budget

Background

Keeping global warming within 1.5-2 °C requires reliable estimates of how much CO2 the land and ocean can absorb, yet evidence suggests that climate change is already altering these natural sinks. Traditional global carbon budgets often omit or simplify processes such as land‑cover change corrections and lateral carbon transfers to inland waters, which can bias estimates of sink strength (capacity to sequester) and remaining carbon space. As atmospheric CO2 concentrations and temperatures rise, it becomes increasingly urgent to understand whether land and ocean sinks are weakening, stabilizing, or intensifying in response to climate forcing. This paper consolidates new observational and modelling advances to reassess the behavior of natural carbon sinks under a warming climate.

Goals and Methods

This study aims to integrate recent advances in observations and process understanding to produce a consolidated global carbon budget and to quantify climate impacts on natural sinks, analyzing the period from 1960 to 2023, with particular emphasis on 2014-2023. The authors combine updated land and ocean observations, process-based models, and corrections for landcover change and lateral carbon export to inland waters, and they revise estimates of the land and ocean sinks accordingly. They reconstruct a land-cover-corrected land sink to adjust for anthropogenic perturbations in land-water carbon transfers and compare resulting sink estimates with previous Global Carbon Budget assessments. Landcover change and lateral carbon export to inland waters, and they revise estimates of the land and ocean sinks accordingly.

Conclusions and Takeaways

The authors show that the natural land sink is smaller than previously thought, land-use emissions are higher, and the ocean sink is about 15% larger than the land sink, aligning with recent oceanic and atmospheric data. They estimate that climate change alone has increased atmospheric CO2 by 8.3 ± 1.4 ppm since 1960 by decreasing sink efficiency. Additionally, climate change and deforestation together have caused major tropical forests in Southeast Asia and parts of South America to switch from net CO2 sinks to net sources. Land-use emissions are elevated, and the ocean sink surpasses the land sink by approximately 15%, consistent with recent evidence. This article concludes that stopping deforestation and limiting warming are essential to prevent further terrestrial carbon loss. Better, consolidated assessments of sources and sinks are vital for tracking policy success and guiding national inventories and global carbon stock estimates.