Weakening carbon reserves can accelerate global warming
2023 was a record year for many indicators of the climate crisis. Not just the global air temperature, which has reached 1.48°C above the pre-industrial period average. Or that of the oceans, which have remained since March on unprecedented values. The concentration of CO2 in the atmosphere has also been accelerating. The reference station, the Mauna Loa Observatory in Hawaii, has recorded an 86% higher body growth than in the last 10 years: 3.37 parts per million compared to 2.42 between 2013 and 2022. And yet, anthropogenic CO2 emissions, still in 2023, have only increased by 0.5%. For an international group of climate scientists, this indicates that last year, the planet’s central carbon sink collapsed.
Carbon sink absorbed 3.5-6 times less CO2 than normal What does that mean? The flow of CO2 between the atmosphere and natural carbon wells has been altered. And the latter absorbed much less carbon dioxide than normal.
Every year, terrestrial carbon sink– i.e. forests, turf and other ecosystems capable of capturing and storing CO2 naturally – remove about one-fifth of the carbon dioxide emitted by human activities, mainly the combustion of fossil fuels. They are, therefore, a “cushion” against rising global warming. Just like the oceans, the other big carbon well on the planet, it absorbs about 1/4 of it.
According to researchers at Tsinghua University in China, Exeter University in Great Britain, Leipzig University in Germany, and the French National Research Council, in 2023 forests and soils worldwide have absorbed only 1.5 – 2.6 billion tons of CO2 (GtCO2). By 2022, they had captured approximately 9.5 GtCO2. The average for the last 10 years is 7.5 GtCO2.
The climate crisis behind the change in carbon flows
By analysing CO2 flows in regional detail, the study’s authors, published in pre-print on July 17 and presented on July 29 at an international conference in Brazil, determined which ecosystems have reduced the most CO2 absorptions. And what are probably the causes behind this phenomenon: all due to the impact of the climate crisis.
The Amazon and Canadian forests were the two carbon reservoirs that absorbed less CO2 than the norm in 2023. An exceptional drought hit the world’s largest rainforest in the second half of the year, while forests in North America have been hit by the worst fire season ever. Rocks have emitted more CO2 than the entire European Union generates in a year. There is also a significant slowdown in the absorption of CO2 in Southeast Asia, another key region for the world’s tropical forests.
“If this collapse repeats over the next few years, we risk witnessing a rapid rise in CO2 and climate change, higher than the models predicted,” warns Philippe Ciais, director of the Laboratory for Climate and Environmental Sciences at the French CNR and co-author of the study.