Just saw the LA Times obituary for the Danish paleoclimatologist Willi Dansgaard [LINK]. Dansgaard was a physicist by training, with a specialty in spectroscopy. He figured out the connection between temperature and oxygen isotope ratio in precipitation which became one of the foundations of paleoclimatatology. He also discovered abrupt climate change when he analyzed early ice cores.
Dansgaard's death comes just after Tamino wrote about glacial cycles in a couple of posts that are worth reading: PART0 PART1 PART1b PART2