The Early Paleogene is recognized as a particularly warm interval in Earth's history. Paleogene proxy climate indicators suggest warm polar and mid-latitude continental interior temperatures, and a reduced latitudinal temperature gradient. Most researchers believe that Early Paleogene climate was driven by forcing fields that act globally (e.g., greenhouse gases). However, modeling work based on this hypothesis has failed to reproduce Paleogene climate as indicated by proxy data. Quite possibly, an ameliorating influence acting directly at the poles would more effectively warm high latitudes, provide an additional heat source to mid-latitude continental interiors, and reduce the latitudinal temperature gradient. Here we present a hypothesis based on the positive phase of the modern Arctic Oscillation; in short, that prolonged low pressure over the Arctic Ocean would have warmed mid-latitude continental interiors and drastically reduced the Arctic Ocean's ice cover, thus producing conditions consistent with proxy climate indicators for the Paleogene greenhouse interval. ¿ 2001 American Geophysical Union