Abstract
In 2023, the CO2 growth rate was 3.37 ± 0.11 ppm at Mauna Loa, 86% above the previous year, and hitting a record high since observations began in 1958[1], while global fossil fuel CO2 emissions only increased by 0.6 ± 0.5%[2,3]. This implies an unprecedented weakening of land and ocean sinks, and raises the question of where and why this reduction happened. Here we show a global net land CO2 sink of 0.44 ± 0.21 GtC yr-1, the weakest since 2003. We used dynamic global vegetation models, satellites fire emissions, an atmospheric inversion based on OCO-2 measurements, and emulators of ocean biogeochemical and data driven models to deliver a fast-track carbon budget in 2023. Those models ensured consistency with previous carbon budgets[2]. Regional flux anomalies from 2015-2022 are consistent between top-down and bottom-up approaches, with the largest abnormal carbon loss in the Amazon during the drought in the second half of 2023 (0.31 ± 0.19 GtC yr-1 ), extreme fire emissions of 0.58 ± 0.10 GtC yr-1 in Canada and a loss in South-East Asia (0.13± 0.12 GtC yr-1 ). Since 2015, land CO2 uptake north of 20°N declined by half to 1.13 ± 0.24 GtC yr-1 in 2023. Meanwhile, the tropics recovered from the 2015-16 El Niño carbon loss, gained carbon during the La Niña years (2020-2023), then switched to a carbon loss during the 2023 El Niño (0.56 ± 0.23 GtC yr-1 ). The ocean sink was stronger than normal in the equatorial eastern Pacific due to reduced upwelling from La Niña's retreat in early 2023 and the development of El Niño later[4]. Land regions exposed to extreme heat in 2023 contributed a gross carbon loss of 1.73 GtC yr-1 , indicating that record warming in 2023 had a strong negative impact on the capacity of terrestrial ecosystems to mitigate climate change.
https://arxiv.org/pdf/2407.12447Article about it (which is why I've dug up this old thread);
Trees and land absorbed almost no CO2 last year. Is nature’s carbon sink failing?
In 2023, the hottest year ever recorded, preliminary findings by an international team of researchers show the amount of carbon absorbed by land has temporarily collapsed. The final result was that forest, plants and soil – as a net category – absorbed almost no carbon.
There are warning signs at sea, too. Greenland’s glaciers and Arctic ice sheets are melting faster than expected, which is disrupting the Gulf Stream ocean current and slows the rate at which oceans absorb carbon. For the algae-eating zooplankton, melting sea ice is exposing them to more sunlight – a shift scientists say could keep them in the depths for longer, disrupting the vertical migration that stores carbon on the ocean floor.
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The 2023 breakdown of the land carbon sink could be temporary: without the pressures of drought or wildfires, land would return to absorbing carbon again. But it demonstrates the fragility of these ecosystems, with massive implications for the climate crisis.
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Only one major tropical rainforest – the Congo basin – remains a strong carbon sink that removes more than it releases into the atmosphere. Exacerbated by El Niño weather patterns, deforestation and global heating, the Amazon basin is experiencing a record-breaking drought, with rivers at an all-time low. Expansion of agriculture has turned tropical rainforests in south-east Asia into a net source of emissions in recent years.
https://www.theguardian.com/environment/2024/oct/14/nature-carbon-sink-collapse-global-heating-models-emissions-targets-evidence-aoeAnd the ominous heading: ‘None of the models have factored this in’
= new reply since forum marked as read