Based on measurements compiled from the past couple of decades on the wetland d13C-CH4 isotopic source signatures from different wetland ecosystems, we have produced a spatially-resolved gridded map. This map distinguishes bogs and fens in the northern high-latitudes, which have dramatically different signatures due to the fundamental differences in hydrology, and C3 and C4 wetlands in the tropics, which utilize different photosynthetic pathways.
![](https://aganesan.blogs.bris.ac.uk/files/2019/11/isotopemap-300x219.png)
We show with this new gridded distribution the effect of not accounting for these variations in global CH4 simulations. Most previous studies either assume a single globally uniform source signature or a value for the tropics and the high-latitudes. These assumptions result in a large bias in atmospheric simulations that are a size comparable to variations in the atmosphere.
![](https://aganesan.blogs.bris.ac.uk/files/2019/11/isotopebias-300x218.png)