The GIEMS-MethaneCentric database: a dynamic and comprehensive global product of methane-emitting aquatic areas

Abstract. The Global Inundation Extent from Multi-Satellites (GIEMS) database first published in 2001 was a key advance toward the accurate representation of wetlands globally by providing dynamic time series of global surface water based on passive microwave observations. This study supplements the second version of GIEMS (GIEMS-2) with other datasets to produce GIEMS-MethaneCentric (GIEMS-MC), a dynamically mapped dataset of methane-emitting waterlogged and inundated ecosystems. We separated open water from wetlands in GIEMS-MC by using the Global Lakes and Wetlands Database version 2 (GLWDv2) while adding unsaturated peatland areas undetected by GIEMS-2. Rice paddies are identified using the Monthly Irrigated and Rainfed Crop Areas (MIRCA2000) product. A specific coastal zone filtering is applied to avoid ocean artifacts while preserving coastal wetlands. GIEMS-MC covers the period 1992–2020 on a monthly scale at 0.25° × 0.25° spatial resolution. The GIEMS-MC product includes two layers of monthly wetland time series – one for flooded and saturated wetlands and another for all wetlands and peatlands – together with seven layers of compatible static maps of open water bodies (lakes, rivers, reservoirs) and seasonal rice paddy maps used in its production. The dominant vegetation and wetland types per pixel are also provided in GIEMS-MC variables. GIEMS-MC is compared to Wetland Area and Dynamics for Methane Modelling (WAD2M), a dataset providing dynamic wetland information. In terms of wetland extent, all wetlands and peatlands in GIEMS-MC and WAD2M show similar results, with a mean annual maximum of 7.7 Mkm2 for GIEMS-MC and 6.8 Mkm2 for WAD2M, with similar spatial patterns in most regions. The GIEMS-MC seamless time series represents a significant advance in wetland representation for methane modelling, although limitations remain in the accurate identification of rice, coastal, and peatland areas. This resource provides harmonized dynamic maps of aquatic methane-emitting surfaces and is available at https://doi.org/10.5281/zenodo.13919644 (Bernard et al., 2024a).