[3] After several years of research, including some at sites in Greenland, Dansgaard returned to the University of Copenhagen's Biophysics Laboratory, where he developed its mass spectrometer to analyse water isotopes.
According to his student Jørgen Peder Steffensen:[3] In June 1952, Dansgaard made a discovery that came to influence the rest of his scientific career.
He discovered that it was possible to determine the temperature of the precipitating clouds by analysing the stable isotopic composition of rain water.
In the following 12 years, he systematically collected water samples from all over the world in collaboration with the Danish East Asia Company, contacts in Greenland, a French expedition under Paul Emile Victor and later the International Atomic Energy Agency and World Meteorological Organization.Dansgaard was the first paleoclimatologist to demonstrate that measurements of the trace isotopes oxygen-18 and deuterium in accumulated glacier ice could be used as an indicator of past climate.
[4] He was the first scientist to extract palaeoclimatic information from the American Camp Century ice core from Greenland drilled by the US army Cold Regions Research and Engineering Laboratory (CRREL).