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Northern peatlands could seriously complicate efforts to cool the planet, especially after a temporary overshoot of the 1.5°C global warming limit, according to new IIASA-led research.

The northern peatlands are vast waterlogged ecosystems that store immense amounts of carbon in deep layers of partially decayed plant matter. While they cover just a fraction of Earth's surface, they contain about one-third of the world's soil carbon, thanks to their unique ability to accumulate thick layers of peat over thousands of years.

The study, co-led by IIASA researchers Biqing Zhu and Chunjing Qiu from East China Normal University, and in One Earth, highlights that although peatlands continue to absorb carbon dioxide (COâ‚‚) as the climate warms, they also release substantial amounts of methane (CH₄), a potent greenhouse gas.

The team used the OSCAR Earth System Model to capture the complex interactions within peatlands and their global impact, and found that these rising methane emissions could offset much of the climate benefit from the peatlands' carbon storage capacity, especially in scenarios where global temperatures exceed 1.5°C before eventually falling back below that threshold.

"Our study aimed to understand the critical role of northern peatlands in global climate change, especially if the world temporarily overshoots the 1.5°C limit," Zhu explains. "Our results indicate that natural systems like peatlands, which are often overlooked in climate plans, can act as accelerators that make it much harder to cool the planet back down. This is a crucial risk for climate policy to consider."

Although peatlands will keep taking up carbon, rising temperatures drive increased methane emissions, which undermine their overall cooling effect on the climate. The researchers found that, in overshoot scenarios, the additional methane released from peatlands effectively cancels out part of their carbon sequestration capacity. This hidden feedback means humanity could need to remove about 10% more carbon from the atmosphere to return to safer climate levels than previously estimated.

This means that if peatlands are left out of climate strategies, policymakers risk severely underestimating how much carbon removal will be needed, particularly if the world temporarily warms beyond 1.5°C.

"Systems like peatlands may have only a small effect on peak warming, making them easy to overlook, but they can make it much harder to bring temperatures back down afterward," notes Zhu. "Overshoot needs serious attention because natural systems often respond in uncertain and irreversible ways."

The team emphasizes that continued international cooperation is essential to refine understanding of these critical Earth system feedbacks and to inform climate policies that can adequately account for overshoot risks.