Special features of ECHAM3_T42_70001anom: This experiment was made with changed SSTs in the N-Atlantik & Pacific. The global response to these boundary conditions was analysed using three variables: surface temperature, zonal wind speed, precipitation. The statistical significance of the changes was tested with a two tailed t-test.Moreover, the significant responses to cooled oceans were compared with geological evidence of a YD oscillation. This comparison revealed a good match in Europe, Greenland, Atlantic Canada and the North Pacific region, explaining the YD oscillation in these regions as a response to cooled N-Atlantic an N-Pacific Oceans. However, the results leave the YD climate in other regions completely unexplained.