Isotope and chemical analyses of the GRIP ice core from Summit, centra
l Greenland, reveal that climate in Greenland during the last intergla
cial period was characterized by a series of severe cold periods, whic
h began extremely rapidly and lasted from decades to centuries. As the
last interglacial seems to have been slightly warmer than the present
one, its unstable climate raises questions about the effects of futur
e global warming.