“Exhaled human breath can contain small, elevated concentrations of methane (CH4) and nitrous oxide (N2O), both of which contribute to global warming,” according to research released last week in the UK journal PLOS.

https://nypost.com/2023/12/19/news/humans-may-be-fueling-global-warming-by-breathing-new-study/?

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Humans Are Fueling Global Warming By Just Breathing, Study Claims

https://www.ndtv.com/science/humans-are-fueling-global-warming-by-just-breathing-study-claims-4680910

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Measurements of methane and nitrous oxide in human breath and the development of UK scale emissions

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0295157