Most forecasting is easier and more reliable in the short run
than over the long haul. Think of weather prediction. (And
history is full of failed long-term forecasts of everything from
oil prices to human population trends.) But for scientists
studying the fate of the vast ice sheets of Greenland and West
Antarctica, the situation seems reversed. Their views of sea
trends through this century still vary widely, while they agree,
almost to a person, that centuries of eroding ice and rising
seas are nearly a sure thing in a warming world. The great
shifts of sea level and temperature through cycles of ice ages
and warm intervals make that clear. I wrote about that consensus
last year in covering the reports released by the
Intergovernmental Panel on Climate Change, but also wrote about
scientists’ frustrations over trying to convey the importance of
a slow-motion disaster. Many researchers are working hard to try
to clarify whether more melting, both on the ice surface and
along the coasts, could greatly speed