Analysis of mean, maximum, and minimum temperature in Athens from 1897 to 2001 with emphasis on the last decade: trends, warm events, and cold events

Abstract

The 105-year (1897–2001) surface air temperature record of the National Observatory of Athens (NOA) has been analyzed to determine indications of significant deviations from long-term average features in the city of Athens. The analysis of the whole record reveals a tendency towards warmer years, with significantly warmer summer and spring periods and slightly warmer winters (an increase of 1.23 and 0.34 °C has been observed in the mean summer and mean winter temperature, respectively). The tendency is more pronounced for the summer and spring maximum temperature, but marginal for the minimum temperature of the cold season. On a monthly basis, a statistically significant (at the 95th confidence level) warming trend has been observed in the average maximum temperature of May and June. The trend analysis for the last decade of the record (1992–2001) revealed a significant increase for both warm and cold seasons, yet maximum and minimum temperature. Extreme temperatures (high/low temperatures above/below a certain threshold value) and extreme events (prolonged extreme temperatures) have also been studied. The number of hot days as well as the frequency of occurrence and duration of warm events have significantly increased during the last decade, while a negative trend is observed in the frequency of low temperatures and the duration of cold events especially after 1960.