Hi @Djibril -
You can use the 2020 LULC map for the “future” input. This is used just to take the difference between whatever you’re defining as “current” (1975, 1995 and 2010) and “future” to calculate sequestration.
The error message says that the size of the pixels in the current land cover map are just slightly different than the size of the pixels in the future land cover map, but they need to be exactly the same. (If this is a requirement for this model, it should be noted in the User Guide, which it isn’t, I’ll look into that.) Try reprojecting your input land use rasters (both current and future) to have cell size of exactly 30m x 30m and that error should go away.
~ Stacie