Ocean and Land Carbon Sinks Slow in Absorbing Emissions
New research indicates that the ocean and land carbon sinks are not absorbing carbon dioxide at increasing rates, which has implications for future climate change projections.
Over the past two centuries, humans have emitted billions of tons of carbon dioxide into the atmosphere by burning fossil fuels, leading to rising global temperatures. The oceans have absorbed 35% of carbon dioxide emissions from fossil fuels since 1990, while forests and other plants have absorbed an additional 13% (The Conversation – Articles (US)). This absorption has helped mitigate the effects of climate change, but new research suggests that the rate of absorption may be slowing. Scientists are concerned about the future behavior of these carbon sinks, as their effectiveness in absorbing carbon dioxide is critical for managing global temperatures and preventing further climate impacts. [1]
Measuring the carbon sinks is a complex and expensive task, as different regions of the ocean and land behave in varying ways. Computer models and satellite data are useful but have limitations, such as the inability to see through clouds or measure deep ocean processes (The Conversation – Articles (US)). A new study published in the journal Science in 2026 used high-precision measurements of atmospheric oxygen and carbon dioxide to quantify the ocean and land carbon sinks. The study found that the ocean carbon sink has been increasing but that the rate of increase is slowing, while the land carbon sink has not shown an increasing trend in recent decades. [1]
Global atmospheric carbon dioxide levels have been rising steadily, with July 2026 recording a concentration of 426.10 parts per million (ppm), compared to 424.09 ppm in July 2025 (gml.noaa.gov). This increase in carbon dioxide levels highlights the growing challenge of managing emissions and the need for better understanding of carbon sinks. Scientists have noted that warmer ocean waters are less effective at absorbing carbon dioxide and that ocean circulation changes can affect the rate of carbon uptake. These findings suggest that future projections of climate change may need to account for the decreasing effectiveness of ocean carbon sinks. [2]
Over the past two centuries, humans have emitted billions of tons of carbon dioxide into the atmosphere by burning fossil fuels, leading to rising global temperatures. According to a study published in Science in November 2026, the world’s oceans have absorbed 35% of carbon dioxide emissions from fossil fuels since 1990, while forests and other plants have absorbed an additional 13% (The Conversation – Articles (US)). These natural carbon sinks play a crucial role in mitigating the impacts of climate change, but scientists warn that their ability to absorb carbon may be diminishing due to rising temperatures and changes in ocean and land dynamics. Measuring these carbon sinks is a complex and expensive task, as different regions of the ocean and land behave in varying ways. [1]
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Global atmospheric carbon dioxide levels have been rising steadily, with July 2026 recording a concentration of 426.10 parts per million (ppm), compared to 424.09 ppm in July 2025 (gml.noaa.gov). This increase underscores the urgency of understanding how carbon sinks will behave in the future. The study also found that the ocean sink has been expanding, meaning the oceans are taking in more carbon dioxide, but that expansion might begin to slow in the coming decades. Meanwhile, the land sink has not shown an increasing trend in recent decades, which was a surprising finding for scientists. [2]
The study used high-precision measurements of atmospheric oxygen (O₂), combined with atmospheric carbon dioxide (CO₂) measurements, to quantify how the ocean and land carbon sinks take up carbon dioxide. This method allows scientists to distinguish between the effects of ocean and land carbon sinks, as each has a different impact on oxygen levels. However, the research also highlights the limitations of current models, which do not always align with real-world observations. Scientists emphasize that improving models and combining multiple measurement approaches will be essential for more accurate predictions of future carbon sink behavior and climate change impacts. [1]
Over the past two centuries, humans have emitted billions of tons of carbon dioxide into the atmosphere by burning fossil fuels, leading to rising global temperatures. The world’s oceans have absorbed 35% of carbon dioxide emissions from fossil fuels since 1990, and the forests and other plants of the world have absorbed another 13% (The Conversation – Articles (US)). This is significant because the oceans and forests act as crucial natural carbon sinks that help slow the pace of climate change. However, the effectiveness of these sinks may be changing as global temperatures increase. [1]
Global atmospheric carbon dioxide levels have been rising steadily, with July 2026 recording a concentration of 426.10 parts per million (ppm), compared to 424.09 ppm in July 2025 (gml.noaa.gov). These measurements highlight the ongoing increase in carbon dioxide levels despite efforts by natural sinks to absorb emissions. The study used high-precision measurements of atmospheric oxygen (O₂), combined with atmospheric carbon dioxide (CO₂) measurements, to quantify how the ocean and land carbon sinks take up carbon dioxide (The Conversation – Articles (US)). This method is essential for understanding how these natural systems are responding to rising emissions. [2] [1]
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Measuring how much carbon is being taken up by the world’s oceans and forests is devilishly difficult and prohibitively expensive. This is because many parts of the land and ocean don’t behave in the same ways. What occurs in one ocean region or forest can be very different from another; and the behavior in one year can be very different in the next, often for reasons scientists do not fully understand (The Conversation – Articles (US)). These complexities make it challenging to predict how carbon sinks will behave in the future, which is crucial for developing effective climate policies. [1]
Measuring how much carbon is being taken up by the world’s oceans and forests is devilishly difficult and prohibitively expensive. This is because many parts of the land and ocean don’t behave in the same ways. What occurs in one ocean region or forest can be very different from another; and the behavior in one year can be very different in the next, often for reasons scientists do not fully understand (The Conversation – Articles (US)). [1]
Computer models can help overcome some of these complexities, but they too have limitations. Satellites can also help, but they cannot see through clouds, nor can they see what is happening in the soil or mid-to-deep ocean. The 10-year running averages for the two global carbon sinks – land and ocean – show the ocean absorbing much more, but that increase in how much it absorbs is slowing. The land sink does not show an increasing trend in recent decades (The Conversation – Articles (US)). [1]
Global atmospheric carbon dioxide levels have been rising steadily, with July 2026 recording a concentration of 426.10 parts per million (ppm), compared to 424.09 ppm in July 2025. These measurements are critical for understanding the role of the oceans and forests in absorbing carbon dioxide emissions from human activities (gml.noaa.gov). [2]
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