Ancient Carbon is Escaping and Altering Climate Change Models: What You Need to Know

A recent international study has changed how we view rivers in the context of climate science. Traditionally, we thought of rivers as speedy pathways for carbon cycling, mainly from recent plant decay. However, new findings reveal that rivers are also significant avenues for ancient carbon that has been stored for centuries or even millions of years.

Published in Nature, the research led by Dr. Josh Dean from the University of Bristol indicates that over half of the carbon emissions from rivers—specifically carbon dioxide (CO₂) and methane (CH₄)—actually comes from long-term carbon reservoirs like deep soils and weathered rocks. This contrasts starkly with the previously held belief that river emissions were primarily derived from recently decomposed plant material.

To arrive at these insights, the study analyzed data from over 1,100 radiocarbon measurements across 700 river sites in 26 countries. Researchers examined the carbon-14 content in river waters to determine the age of released carbon. They found that about 60% of river CO₂ emissions come from ancient sources, suggesting a major leak of carbon that requires a reassessment of global carbon models.

Dr. Dean noted the implications of the study: “The results took us by surprise because it turns out that old carbon stores are leaking out much more into the atmosphere than previous estimates suggested.” He emphasized that this unexpected release could mean that land ecosystems must absorb more CO₂ than previously thought to keep the atmosphere balanced.

Globally, rivers emit around 2 gigatons of carbon annually, with about 1.2 gigatons coming from these ancient sources—a figure comparable to the total carbon uptake by all terrestrial ecosystems. This “leak” is significant enough to warrant serious attention in climate science.

Different factors contribute to this ancient carbon release. It can be mobilized from deep soil layers or via the slow weathering of sedimentary rocks. As such, understanding how this ancient carbon interacts with the atmosphere is critical for future climate models.

These findings suggest that forests and soil’s ability to act as carbon sinks may be even more crucial—and more fragile—than previously recognized. With ongoing climate change, land use changes, and thawing permafrost, the risk of releasing this old carbon could increase.

In summary, this research opens a new chapter in understanding Earth’s carbon balance. It underscores the importance of considering ancient carbon emissions in climate science and policy-making, especially as we navigate the complexities of climate change.

For further reading, you can check the full study in Nature here.

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