Author(s)

MARTIN SALIBA, ALFRED MICALLEF

Abstract

Measurements of concentrations of various greenhouse gases were collected over a time period of 11 years (2012–2023). The data were collected at Giordan Lighthouse monitoring station on the island of Gozo, forming part of the Maltese archipelago, in the central Mediterranean region. The associated data analysis and observations are presented. It turns out that the methane concentration is increasing at a relatively substantial rate of 9.6 parts per billion by volume (ppbv) per year. Similarly, carbon dioxide is showing a mean increase of 2.15 parts per million by volume per year. Similar trends have been reported in the eastern Mediterranean region. A minimal increase is observed in carbon monoxide concentration and atmospheric water content, at a rate of 0.32 ppbv per year and 0.02% per year, respectively. Both methane and carbon dioxide show maxima in winter and minima during the summer months. Carbon monoxide also shows a maximum in winter but a minimum during summer and autumn. However, carbon monoxide exhibits a secondary maximum in August. In contrast, atmospheric water content presents a clear maximum in summer and a minimum in winter as expected for the Mediterranean climate. With respect to wind direction, methane, carbon monoxide and carbon dioxide clearly show maxima when the prevailing wind is from the north sector and secondary broad maxima when the wind is blowing from the south-east sector. Greenhouse gases exhibit a clear diurnal variability with a maximum in the early morning and a minimum in the afternoon. Both the diurnal maximum and minimum of carbon dioxide precede that of carbon monoxide.

Keywords

central Mediterranean, greenhouse gases, methane, carbon monoxide, carbon dioxide, water vapour