Climate change. CO₂ sources and sinks

As COP30 gets underway, scientists publish an adjusted estimate of natural and anthropogenic CO₂ sources and removals in the journal Nature. Among the authors is Pierre Regnier, who coordinated the continental-marine interface part of the study.

Correct estimation of natural and anthropogenic CO₂ sources and sinks is necessary to assess the effectiveness of climate policies and to detect the responses of carbon sinks to climate change. However, notable inconsistencies in the estimates persisted, limiting confidence in the interpretation of trends and their controlling factors.

Published in the journal Nature, a study presents and integrates recent advances in this field, based on new observational data and a better understanding of the underlying processes. "These advances increase confidence in the global anthropogenic CO₂ budget that is essential for effective climate policy", emphasizes Pierre Regnier - BGEOSYS, Faculty of Science - co-author of the study.

In particular, the study shows that net anthropogenic emissions linked to land use change, in particular deforestation, have been underestimated.

New observational data in the marine realm have also determined that the oceanic sink pumps out 15% more CO₂ than the continental sink. The latter was overestimated, the negative effect of climate change being greater than previously anticipated. The overestimation was also due to the failure to take into account the reversible nature of anthropogenic CO₂ capture by terrestrial ecosystems, with a considerable fraction of carbon being transferred to the global water system, only to be re-emitted to the atmosphere or transferred to the open ocean.

This part of the study, coordinated by ULB - Pierre Regnier, BGEOSYS, Faculty of Science - and integrated for the first time into the global anthropogenic CO₂ budget, is based on a meta-analysis of available data and modelling of physical and biogeochemical processes to determine the spatial distribution and temporal evolution of carbon stocks within the Earth system.