The several-millennial cooling in central Greenland since the middle Holocene probably was caused by a trend to reduced oceanic heat transport as well as by orbital forcing, based on several lines of evidence. The late-Holocene trend is similar in many ways to the older coolings associated with abrupt, millennial climate changes. Climate records from Greenland ice cores indicate that both abrupt and gradual coolings involved: (i) greater temperature decrease in winter than in summer; (ii) greater accumulation-rate decrease in winter than in summer causing normally calibrated ice-isotopic changes to underestimate temperature changes; and (iii) increasing interannual climate variability. Paleoclimatic data and model results show that abrupt coolings have been linked to reduction in North Atlantic oceanic heat transport; we suggest that decreasing North Atlantic oceanic heat transport has also contributed to the Holocene trend. Gradual reductions in ocean heat transport precede abrupt reductions in both paleoclimatic records and model results, so it is likely that the natural trend has been toward the threshold for abrupt change in the late Holocene.