Atmospheric methane lifetime during the Last Glacial Maximum was reduced owing to dust-mediated chlorine chemistry.

Atmospheric methane lifetime during the Last Glacial Maximum was reduced to 7.8 years, 20% shorter than today, due to dust-mediated chlorine chemistry.

• Why it matters: Understanding methane's decline during glacial periods is crucial for accurate climate modeling, yet the role of atmospheric sinks has been underestimated, creating gaps in our knowledge.
• What they did: The study used ice core data and modeling to show that mineral dust and sea salt aerosols produced chlorine radicals that increased methane removal, with chlorine accounting for about 15% of global methane loss during the LGM.
• The result: This work demonstrates that enhanced chlorine-driven sinks can explain methane variability in glacial times without major source changes, emphasizing the importance of chlorine chemistry in past climate dynamics.