The nearly global retreat of the Earth's ice cover is a matter of concern to people everywhere. The changes are most marked in northern latitudes with accelerated melting of the Greenland ice sheet, widespread thawing of the permafrost, and the rapid decrease of summer sea ice in the Arctic Ocean. Most mountain glaciers and ice caps are wasting away. In high southern latitudes, changes in the ice are more muted except for the land ice of the Antarctic Peninsula and the Pine Island Bay region. In the Southern Ocean, by contrast, the sea ice cover is slowly expanding. Do these large changes represent early warning signs of rapid global warming, recovery from the Little Ice Age, or the natural evolution of the present interglacial period?