Nowadays, climate change and atmospheric pollution are two of humanity's most significant challenges. Greenhouse gases (GHGs) are responsible for climate change, and they create effects that are mostly irreversible. Therefore, monitoring and reducing such emissions are compulsory for the preservation of the environment for future generations. The European Union took action in this direction. The article presents the evolution of the total GHGs trend, from 1990 to 2021, in the EU countries and their associates. Trend analysis and grouping of the countries using different clustering techniques are performed. The analysis of the existence of greenhouse gases (GHGs) series' trend, in 30 countries from Europe, showed that the GHG emissions decreased from 1990 to 2021 in only 17 countries. The annual series, built using the data reported by each country each year, does not present a specific trend. After grouping the countries in clusters by k-means and hierarchical clustering, the representative series for the annual recorded values in the 30 studied countries, called Regional series (RegS), is built using series selected from the cluster with the highest number of elements. The same algorithm provides the Representative Temporal series (TempS), which selects specific years after clustering the annual GHG series.
Keywords: clustering; greenhouse gases (GHGs); regional series; representative temporal series.