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.