Is Quitt's climate classification still relevant? Challenges posed by recent climate change

Climate classifications based on fixed threshold values are increasingly challenged under recent climate change, yet remain broadly used. Accordingly, this contribution assesses the relevance of the widely used Quitt climate classification for the Czech Republic as a representative region of Central Europe. The original methodology, derived from the 1901–1950 period, was re-applied to a gridded dataset of multiple climate variables based on homogenised station series for the 1961–1990 and 1991–2020 periods to produce an updated version of the Quitt climate classification. For the 1991–2020 period, results indicate a significant expansion of the Warm group of climatic regions (by 30%) at the expense of the Moderately Warm and Cold groups. Following these spatial shifts, the Updated Quitt climate classification lost its explanatory power during this period. The original classification criterion (matching ≥ 12 of 14 variables) was met in only 5% of the territory of the Czech Republic due to a loss of internal consistency between temperature and precipitation characteristics: rising temperatures shifted climatic regions to higher elevations, while precipitation totals remained stable. The unsuitability of the original Quitt classification method emphasises the need for multivariate statistics and clustering-based approaches that better reflect contemporary spatiotemporal climate variability in Central Europe.