Atmospheric methane lifetime during the Last Glacial Maximum was reduced owing to dust-mediated chlorine chemistry.
basic_science · Level V
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- Record sourced from PubMed, PMID 42752137.
- Also identified by DOI 10.1126/science.aec4071.
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Abstract
Atmospheric methane (CH<sub>4</sub>) plays a central role in Earth's climate, yet the drivers of its decline during the high-dust conditions of glacial periods, such as the Last Glacial Maximum (LGM), remain uncertain. Previous explanations imply source-driven changes, assuming an atmospheric lifetime comparable to that of present day. Recent work shows that interactions between mineral dust and sea salt aerosols produce CH<sub>4</sub>-removing chlorine radicals. In this work, we show that during the LGM, CH<sub>4</sub> lifetime shortened to 7.8 years, 20% lower than that of present day. Chlorine contributed ~15% of global CH<sub>4</sub> loss, fourfold that of present day. Our results reproduce ice core CH<sub>4</sub> isotopic evidence, demonstrating that stronger-than-assumed atmospheric sinks can explain CH<sub>4</sub> variability without invoking substantial source changes, highlighting the overlooked role of chlorine chemistry in the glacial CH<sub>4</sub> budget.