Low latency carbon budget analysis reveals a large decline of the land carbon sink in 2023
Science China Press
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.
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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.
Net land and ocean CO2 flux anomalies for each quarter in 2023 compared with the 2015-2022 average for bottom-up models (left column) and the OCO-2 inversion (right column).
Positive values represent increased flux from the atmosphere to the land or ocean (carbon sink).
Credit
©Science China Press
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
DOI
Scientists predicted the spatial-temporal dynamics of soil microbial-derived carbon stocks
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(a) Global map of the predicted MDC stock distribution for the year 2018, along with the changes from 1981 to 2018. The white areas in the left panel and the dark areas in the right panel are the areas with low confidence projections. (b) The relative rates of change in MDC stocks as percentages per annum and per degree Celsius. The dark areas are the areas with low confidence projections. (c) Status of MDC stocks between 1981 and 2018. Bivariate plot comparing the relative rate of change in MDC stock (% per year) against the quantity of MDC stocks. The status categories for the rate of change were determined using confidence intervals, while the MDC stock status groups were established based on quantile distributions (divided into three equal parts). The white areas are the areas with low confidence projections.
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Soil organic carbon (SOC) is the largest carbon pool in terrestrial ecosystems and plays a crucial role in mitigating climate change and enhancing soil productivity. Microbial-derived carbon (MDC), accounting for about half of the total SOC pool, is the main component of the persistent SOC pool. However, our limited understanding of the spatial and temporal dynamics of MDC stocks at the global scale hampers our ability to assess the long-term effects of global warming on persistent SOC sequestration.
To fill this gap, the research team led by Jiabao Zhang and Yuting Liang, researchers at the Nanjing Institute of Soil Science, Chinese Academy of Sciences, in collaboration with Shenyang Institute of Applied Ecology, Aarhus University (Denmark), University of Kassel (Germany), ETH Zurich (Switzerland), University of Oklahoma (USA), and other domestic and foreign research units, predicted the spatial-temporal dynamics of soil microbial-derived carbon stocks. The relevant research results are described as " Global decline in microbial-derived carbon stocks with climate warming and its future projections", published online in National Science Review.
In this study, this team compiled an extensive global dataset and employed ensemble machine learning techniques to forecast the spatial-temporal dynamics of MDC stocks across 93.4% of the total global land area from 1981 to 2018. This work revealed that for every 1°C increase in temperature, there was a global decrease of 6.7 Pg in the soil MDC stock within the predictable areas, equivalent to 1.4% of the total MDC stock or 0.9% of the atmospheric C pool. The tropical regions experienced the most substantial declines in MDC stocks. They further projected future MDC stocks for the next century based on shared socioeconomic pathways, showing a global decline in MDC stocks with a potential 6-37 Pg reduction by 2100 depending on future pathways.
MDC is crucial for maintaining the long-term stability of SOC. A decrease in MDC suggests that a substantial portion of the stable SOC could be released into the atmosphere as carbon dioxide (CO2), creating a positive feedback loop between atmospheric and soil carbon reservoirs.“These results offer an empirical foundation for refining the temperature dependency of MDC stocks within atmosphere‒soil carbon cycle models.” Liang says.
This study underscores that global warming will lead to a decrease in global MDC stocks, which could have severe ecological repercussions for climate change, food security, and ecosystem integrity. The researchers recommend integrating the response of MDC stocks to warming into socioeconomic models to enhance confidence in selecting sustainable pathways.
Projections of the total global microbial-derived carbon (MDC) stock under various shared socioeconomic pathways 
SSP126 represents a sustainability scenario in which the world is gradually transitioning toward sustainable practices. SSP245, the middle-of-the-road scenario, maintains trends closely aligned with historical patterns. SSP370, the regional rivalry scenario, emphasizes domestic or regional issues due to increased nationalism and conflicts. Finally, SSP585 is a fossil-fueled development scenario characterized by large-scale exploitation of fossil fuels that intensifies environmental degradation and climate change.
Credit
©Science China Press
See the article:
Global decline in microbial-derived carbon stocks with climate warming and its future projections
https://doi.org/10.1093/nsr/nwae330
Journal
National Science Review
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