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Radiative budget of the atmosphere

The Intergovernmental Panel on Climate Change (IPCC) has clearly pointed out that significant uncertainties for a comprehensive understanding of the planetary radiative budget, and of the possible influence of changes of the atmospheric composition induced by human activities still exist. Although the role of greenhouse gases and their influence appears well established, the role played by other parameters is still not adequately known. Some processes are only marginally known, and fundamental uncertainties still exist.

The figure below is extracted from the IPCC report prepared in 2001. The vertical bars indicate the estimates of the annual average radiative forcing produced by changes in atmospheric composition (or other phenomena) occurred during the last 250 years. Uncertainties on the estimates are indicated as error bars; the level of scientific understanding is also reported below each considered phenomenon.

It is interesting to emphasize that all the relevant parameters reported in the graph, except land use and solar changes, are measured and studied from Lampedusa (not all continuously). The level of scientific understanding is very low for all processes that involve aerosols, except sulphates, for aviation induced changes on high level clouds, for land use and solar changes. Largest uncertainties exist, however, on the radiative effects (direct and indirect) produced by aerosols. A large uncertainty is associated with the mineral dust, for which no estimate of the forcing is available.

Lampedusa is an excellent site to conduct experiments aimed at reducing uncertainties and allowing a better understanding of the radiative processes. For this reason, combined observations of many atmospheric parameters (total ozone, aerosol properties, greenhouse gases, water vapour, shortwave and longwave radiation fluxes, broadband and narrowband, cloud cover, and meteorological quantities) are performed with a variety of instruments.

On the basis of these observations several studies on the optical properties, distribution, and radiative effects of the aerosol, on the influence of the global carbon cycle on the CO2 distribution in the Mediterranean, and on the behaviour of the ultraviolet radiation have been carried out up to now.