Climate Warming in the Eastern Mediterranean: A Comparative Analysis of Beirut and Zahlé (Lebanon, 1992–2024)

The Eastern Mediterranean region is experiencing accelerated climate warming, yet localized patterns remain poorly understood, particularly in areas with complex topography. This study examines long-term air temperature trends from 1992 to 2024 at two sites in Lebanon: Beirut Airport (urban–coastal) and Houch Al Oumaraa station in Zahlé (inland–valley). Using homogeneity testing, linear regression, and the Mann–Kendall trend test, we assess trends in minimum, maximum, and mean temperatures. The results show a strong and statistically significant warming trend in Beirut, with mean temperatures rising by +0.536 °C per decade and minimum temperatures showing the steepest increase (+0.575 °C/decade). In Zahlé, the warming trend is less pronounced, particularly for maximum temperatures (+0.369 °C/decade), while minimum temperatures increased by +0.528 °C/decade. Data from fixed stations and drone-based vertical profiling in Zahlé confirmed the presence of cold-air pooling and thermal inversions, which moderate air temperatures and may contribute to a subdued warming trend. The strongest inversion recorded in 2022 reached 6.7 °C between ground level and an altitude of 500 m. In contrast, the urban heat island (UHI) effect in Beirut and Zahlé appear to drive nighttime warming, particularly in summer and early autumn months. These findings highlight the roles of topography and urbanization in shaping local climate trends.