ABSTRACT
The problem of external impacts on the climatic system, and, in particular, anthropogenically induced climate changes, is now of great concern. This chapter discusses most important cases of external forcings determined by increased CO2, by other greenhouse gases and by volcanic eruptions. There are numerous unsolved problems connected with various physical aspects of climatic impacts. In order to make reliable predictions of climate change under realistic scenarios of slow changes in the radiative forcing, it is necessary to take the oceanic behaviour properly into account. An important role has been emphasized of simple climate models (energy-balance, radiative-convective) in the identification of most important fields of the application and interpretation of the results obtained with the use of sophisticated three-dimensional models. The evolution of the global mean surface air temperature reflects a rapid warming of the atmosphere due to a CO2 doubling, followed by a slower warming of the atmosphere and the ocean.
