Atmospheric constraints on global emissions of methane from plants

We investigate whether a recently proposed large source of CH_4 from vegetation can be reconciled with atmospheric measurements. Atmospheric transport model simulations with and without vegetation emissions are compared with background CH_4, δ^(13)C-CH_4 and satellite measurements. For present–day CH_4 we derive an upper limit to the newly discovered source of 125 Tg CH_4 yr^(−1). Analysis of preindustrial CH_4, however, points to 85 Tg CH_4 yr^(−1) as a more plausible limit. Model calculations with and without vegetation emissions show strikingly similar results at background surface monitoring sites, indicating that these measurements are rather insensitive to CH_4 from plants. Simulations with 125 Tg CH_4 yr^(−1) vegetation emissions can explain up to 50% of the previously reported unexpectedly high CH_4 column abundances over tropical forests observed by SCIAMACHY. Our results confirm the potential importance of vegetation emissions, and call for further research.

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