SUMMIT, Greenland — Working poles apart--on the crystal crown of the Arctic icecap and on the ice domes of Antarctica--researchers are coming to grips with Earth's frozen past in order to predict its future.
For scientists trying to learn how global warming may affect the climate's course, understanding the character and chemistry of the ice and snow at the planet's extremities has taken on an unusual urgency.
The information they seek could be critical to efforts to curb the burning of fossil fuels and industrial emissions. To stave off global warming, world leaders are preparing to meet in November to prepare the first international controls on emissions of greenhouse gases such as carbon dioxide.
Recent studies of prehistoric ice in Greenland suggest that the world's climate may be balanced on a knife's edge--subject, with almost no warning, to potentially devastating temperature swings causing disasters ranging from floods to crop failures.
Based on their analysis of ancient ice, some scientists are concerned that any human-made changes in the delicate balance of the atmosphere could trigger quick, catastrophic climate changes that could take as little as a year or two.
In drilling completed here four years ago, researchers funded by the National Science Foundation and the European Science Foundation have tapped an archive of ice and snow that records a quarter-million years of winter and summer seasons, as layer upon layer of prehistoric snow was compressed in a frigid parfait of time.
Each core is a diagnostic probe of the past--a cylinder up to two miles long trapping information about conditions in the atmosphere that prevailed when the crystals first formed as falling snow.
These cores offer the clearest picture so far of how the weather has changed. They are the benchmark by which the history of the planet's climate is measured and its future mapped.
They reveal hints that the effect of any global warming might, paradoxically, trigger cold weather severe enough to cause a global winter lasting years. The shift from the warm contemporary climate to an ice age could take less than a human lifetime.
"It raises the possibility that, by putting out greenhouse gases, humans may make the climate unstable and plunge us in as little as a decade into severe cold periods," said Kendrick Taylor at the Nevada Desert Research Institute, chief scientist for a consortium of 15 universities using ancient ice cores to investigate climate.
