image: (a) Growth rate from marine boundary layer surface stations (MBL, blue bars) and the Mauna Loa station (MLO, dark blue squares). (b) Global CO2 budget obtained with historical fossil fuel and cement CO2 emissions and our estimates of land and ocean sinks in 2023, and the MBL / MLO CO2 annual growth rates. Our estimates are based on simulations by emulators of the ocean sink, simulations of the land sink by three dynamic vegetation models forced by low latency climate input data (their mean sink in 2019-2022 being adjusted to equal the median of 16 models used in the latest Global Carbon Budget edition). The ocean and land sinks in the inside bars are from the OCO-2 high resolution atmospheric inversion. The difference between the stacked bars at the bottom and the red curve (-1 x Fossil emissions) is the imbalance of the budget.
Credit: ©Science China Press
In 2023, global land carbon sinks—the Earth’s forests, soils, and vegetation that absorb CO2—experienced a dramatic decline, as revealed by a study published in National Science Review by several international research teams. Using dynamic global vegetation models, satellite fire emissions, OCO-2 satellite measurements, and ocean model emulators, the study provides a fast-track carbon budget for 2023, identifying unprecedented weakening of land carbon sinks.
“In 2023 the accumulation of CO2 in the atmosphere is very high and this translates into a very, very low absorption by the terrestrial biosphere,” says Philippe Ciais, a researcher at the French Laboratory of Climate and Environmental Sciences, who was an author of the most recent paper. “In the northern hemisphere, where you have more than half of CO2 uptake, we have seen a decline trend in absorption for eight years,” he says. “There is no good reason to believe it will bounce back.”
The land sink dropped to 0.44 ± 0.21 GtC yr-1, driven by extreme heat, wildfires, and a moderate El Niño. Particularly, Canadian wildfires contributed 0.58 ± 0.10 GtC, while the Amazon drought caused an additional 0.31 ± 0.19 GtC loss.
Despite the decline on land, the ocean sink increased slightly by 0.10 GtC yr-1 compared to 2022, largely due to El Niño suppressing CO2 emissions in the Pacific Ocean. However, the rapid reduction in land carbon sink raises concerns about future climate stability, as the models used for climate predictions may not fully account for such sudden shifts in carbon sinks.
The findings underscore the importance of strengthening global carbon sequestration efforts. The authors call for urgent measures to protect and enhance carbon sinks, alongside drastic reductions in fossil fuel emissions, to avoid further destabilization of the climate system.
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See the article:
Low latency carbon budget analysis reveals a large decline of the land carbon sink in 2023
https://doi.org/10.1093/nsr/nwae367
Journal
National Science Review