Conclusions can be drawn about past environmental changes from telltale footprints left in environmental records. We are following one such hot lead in our investigations of the 3-km-long Greenland ice core. Layer for layer, the ice is examined to determine the concentrations of the radionuclide beryllium-10 (10Be). From such data it is possible to obtain information about past climate changes. About 10,000 ice samples have been prepared by the EAWAG laboratory in recent years for measurement in the ETHZ/PSI accelerator mass spectrometer.