To gain a full picture of the Spanish (and European) GHG balance, understanding of CH₄ emissions in different regions is a critical challenge, as is the improvement of bottom-up inventories for all European regions. This study uses, among other elements, GHG, meteorological and ²²²Rn tracer data from a Spanish region to understand the main causes of temporal variability of GHG mixing ratios. The study can offer new insights into regional emissions by identifying the impacts of changing sources.