Earth's Lands Suck Carbon Again - For Now
A new study estimates that land ecosystems absorbed more carbon than their recent average, slowing the rise of atmospheric CO2. A forecast strong El Niño could put that recovery under fresh pressure.
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Oct 13, 22:00 UTC ·
875 words
Earth's land ecosystems recovered their carbon uptake in 2025, a new study estimates, helping slow the rise of atmospheric CO2 even as fossil-fuel emissions increased. [2]
Forests, grasslands and other land ecosystems absorbed a net 2.36 billion tonnes of carbon, according to the study. That was 0.71 billion tonnes above the 2015-2022 average, a sharp reversal after two years in which the land sink had faltered. [2]
The recovery matters because land and oceans have together removed more than half of the CO2 emitted by human activities, according to researchers cited by New Scientist. When those natural sinks weaken, more of our emissions stay in the atmosphere. [1]
Philippe Ciais, the study's lead author, told New Scientist that El Niño and Amazon fires had nearly cancelled the global land sink in 2023 and 2024. More normal conditions, especially in Africa and the Amazon, allowed plants to recover their capacity to absorb carbon in 2025, he said. [1]
Mike O'Sullivan of the University of Exeter described 2024 as an "extreme year" and the rebound that followed as a "massive recovery." He warned that bouncing back after a shock does not establish the land sink's long-term resilience to climate change. [1]
More emissions, slower atmospheric growth
The clearest sign of the turnaround was in the air. NOAA observations of air over the oceans put the increase in atmospheric CO2 at 2.06 parts per million in 2025, down from a record 3.76 in 2024. The 2025 increase was also below the 2015-2022 average of 2.47 parts per million. [2]
That means CO2 accumulated almost 45% more slowly than in the previous year. It was still accumulating. A slower rise does not mean the concentration fell. [2]
Meanwhile, fossil-fuel CO2 emissions rose 0.7%, reaching 10.38 billion tonnes of carbon in 2025. Ocean uptake stayed similar to its 2024 level. The study identifies the land's renewed absorption as the main reason atmospheric CO2 growth slowed despite the increase in emissions. [2]
Those figures measure the mass of carbon contained in CO2, rather than the mass of the whole gas. The distinction keeps the emissions and uptake figures on the same basis.
The land sink is an annual balance. Plants draw CO2 from the atmosphere as they grow, while decomposition and fires return carbon to the air. Add those flows together and land can either absorb carbon overall or release it.
The balance changes with conditions from one year to the next. [1]
In 2025, that balance improved by an estimated 2.81 billion tonnes of carbon compared with 2024. The shift was bigger than the entire net uptake recorded for 2025, showing how far the system had swung. [2]
A recovery spread unevenly
The tropics supplied a major part of the change. Tropical lands went from releasing more carbon than they absorbed in 2024 to absorbing more than they released in 2025. Uptake also strengthened across much of Africa and northern Eurasia. [2]
Across areas where the sink had weakened substantially in 2023 and 2024, about 80% showed at least some recovery. But the return was uneven. Tropical recovery exceeded 100% of the earlier loss, while recovery in the northern regions outside the tropics was incomplete. [2]
Water appears in the evidence too. Regional changes in carbon uptake varied alongside measurements of water stored on land from the GRACE satellite mission. Ciais's account of improving conditions in Africa and the Amazon fits that pattern. [2] [1]
The study, titled "Low latency global carbon budget reveals strong land sink recovery in 2025," was submitted to arXiv on September 28, 2026, by Ciais and 34 co-authors. It combines three global vegetation models with four estimates that work backwards from atmospheric CO2 observations to infer carbon uptake and release. Those atmospheric estimates use observations from the OCO-2 satellite. [2]
The work is a preprint, with no peer review or journal publication reported in its submission record. Its methods agree on a strong rebound but differ on its size: the vegetation models estimate uptake of 2.04 billion tonnes of carbon, against 2.68 billion from the atmospheric calculations. The combined estimate is 2.36 billion tonnes, with a reported uncertainty of 0.16 billion tonnes. [2]
That gives the recovery support from different approaches, while leaving room for the headline number to change as the work is assessed.
The next weather test
The rebound bought relief from faster CO2 accumulation for one year. It offers no reason to count on natural systems absorbing an ever-growing emissions bill.
Researchers cited by New Scientist estimate that the land sink is already 25% smaller than it would have been without climate change and natural variability. They expect the land biosphere to become a net carbon source within several decades unless human-driven emissions taper off. [1]
A more immediate threat is another El Niño, the recurring warming of the tropical Pacific that shifts weather patterns. New Scientist reports that a very strong event is forecast to persist into 2027, bringing extreme heat and drought to important land sinks, including the Amazon.
Researchers warn that carbon uptake could fall sharply next year. That is a forecast, not an observed effect on the 2025 recovery. [1]
The next test is whether recovering ecosystems can keep absorbing carbon through renewed heat and drought. The 2025 figures show that a strong rebound is possible. The forecast for 2027 will test how long it lasts. [2] [1]
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