Climate simulations must be extended over longer periods, in many cases over several decades. This is only possible at the expense of lower spatial resolution. The atmospheric initial state is of less importance than an adequate representation of climate system components beyond the purely atmospheric part, e.g. the ocean, the cryosphere or the biosphere. The inclusion of short lived trace substances (like ozone or aerosols) as an interactive component of climate models is becoming increasingly important. This poses a new scientfic challenge as these substances do not only force on the radiative balance of the climate system but are themselves modified by feedback changes of basic meteorological parameters.
In our institute most applications are performed with the ECHAM climate model.