Interannual variability of atmospheric CO2 in the Mediterranean: Measurements at the island at Lampedusa

TitleInterannual variability of atmospheric CO2 in the Mediterranean: Measurements at the island at Lampedusa
Publication TypeArticolo su Rivista peer-reviewed
Year of Publication2003
AuthorsChamard, P., Thiery F., Di Sarra Alcide, Ciattaglia L., De Silvestri L., Grigioni P., Monteleone F., and Piacentino S.
JournalTellus, Series B: Chemical and Physical Meteorology
Keywordsannual variation, Atmospheric chemistry, Carbon dioxide, El Nino-Southern Oscillation, greenhouse gas, Italy, wind direction

The atmospheric concentration of carbon dioxide and other greenhouse gases has been measured weekly since 1992 at the island of Lampedusa, in the Mediterranean sea. Lampedusa is a small island located approximately 100 km east of Tunisia, and 250 km south of Sicily. The 10-yr CO2 data set has been analysed to quantify trends, and characterize semi-annual, annual and inter-annual variability. The data show an average trend of + 1.7 ppmv yr-1; the average annual cycle has an amplitude of about 9 ppmv. In the period of investigation the annual growth rate varies between 0.5 and 4.5 ppmv yr-1, and the amplitude of the annual cycle between 7 and 11 ppmv yr-1. By comparing the observed growth rate with recent estimates of carbon dioxide emissions, it is calculated that 58-61% of the emitted CO2 remains in the atmosphere. The CO2 growth rate appears to be related to large-scale dynamic phenomena, primarily El Nin̄o/Southern Oscillation (ENSO). An evident signature of the 1997-98 El Nin̄o is apparent in the CO2 record, and corresponds to a weakening of the exchange with the biosphere. A high correlation between the global average temperature and the 12-month average carbon dioxide growth rate is also found. Wind direction displays a significant inter-annual variability throughout the measurement period, possibly influencing the observed evolution of the CO2 concentration.


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