CLIMATE SCIENCE: Methane Mystery

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Science  23 Jan 2009:
Vol. 323, Issue 5913, pp. 438c-439c
DOI: 10.1126/science.323.5913.438c

Methane is a powerful greenhouse gas, implicated as a cause of many episodes of climate change in the past and also as a major factor in Earth's contemporary radiative balance. Nonetheless, we still lack an adequate understanding of the global atmospheric methane budget, and in particular the strength of its sources. Recent research suggested that plants were a major source of methane, supplying as much as almost half of the methane released to the atmosphere; the results implied an unknown biochemical pathway for methane production in plants. Nisbet et al. have performed additional experiments, in chambers that allow careful control of the growing environment, which show that plants do not produce appreciable quantities of methane; genetic analyses moreover revealed no genes that would indicate the presence of any known methane biosynthesis pathway. Instead, the authors suggest that previous observations of methane production may have been reflecting the spontaneous breakdown of plant material under high ultraviolet stress conditions or the transpiration of water containing dissolved methane. They conclude that plants are not a major source of global methane production. — HJS

Proc. R. Soc. London Ser. B 10.1098/rspb.2008.1731 (2009).

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