Earth's Cryosphere: Current State and Recent Changes^*

Earth continues to have a third of the ice that it had at the peak of the last ice age, although that ice continues to decrease, as it has, overall, for the past 18,000 years. Over the last 100 years, the retreat signal has been especially strong in ice shelves of the Arctic and along the Antarctic Peninsula, with a more mixed signal elsewhere. For instance, since the early 1990s, the massive Greenland and Antarctic ice sheets have thinned along the coasts but thickened in the interior, and since the late 1970s, sea ice has decreased in the Arctic but increased (slightly) in the Antarctic. Major difficulties in the interpretations of the climate record come from the high interannual variability of most cryosphere components and the lack of consistent long-term global data records; the latter problem is now being slowly remedied, in part, through satellite technology.