Background information
In addition to long-lived greenhouse gases such as CO2,
short-lived species in the atmosphere cause important climate forcings. These include
aerosols, which cause positive and negative forcings (warming and cooling tendencies,
respectively) through the absorption and scattering of solar radiation. Moreover, ozone
is increasing throughout the troposphere, which causes a positive climate forcing, thus
adding to global warming. Aerosols and ozone are also major components of regional pollution
that deteriorates air quality. The recognition that these climate and air quality issues are
linked is growing. For example, large-scale transports of regional air pollution affect the
global background so that air quality standards in other regions are more easily exceeded.
Obviously, the problem is complex, from a scientific as well as a policy perspective.
According to model calculations, the Mediterranean is one of few regions in the world that
stand out both in aerosol climate forcing and photochemical ozone formation (see Figure below).
Especially in summer, the combination of emission transports from Europe, low cloudiness and
high solar radiation provides optimum conditions for pollutant build-up and radiation extinction
by aerosols.
Only few measurements have been performed in the Mediterranean region although these
are prerequisite to perform process studies and to test the simulations with
transport-chemistry models. Therefore, during August 2001 an intensive field campaign
will be conducted to extend the available data sets.