Ancient Greenland DNA Hints at Possible Global-Warming Loophole

An international team of scientists, drilling deep into the ice layers of Greenland, has found DNA from ancient spiders and trees, evidence that suggests the frozen shield covering the immense island survived the earth's last period of global warming.

When we talk about global warming, it should be kept in mind that "warm" periods in our planet's history, known as interglacials, have lasted as little as eight thousand years (the interglacial we're living in at the moment-the Holocene- has passed its ten thousandth anniversary). Before 50 million years ago, Earth had no regular ice ages, but when they did occur, they were monsters.

Earlier ice cores from Greenland have provided a detailed history for the past 100,000 years. The data shows that the planet has lurched violently between periods of warmth and frigid ice with temperature swings fluctuating by as much as 15 degrees in ten years altering rainfall and living conditions that suggest a vast and unforgiving feedback loop involving the oceans and patterns of ocean currents.

A detailed analysis of surviving genetic fragments locked in the ice of southern Greenland shows that somewhere between 450,000 and 800,000 years ago, the world's largest island really was green, before Ice Age glaciers enshrouded vast much of the Northern Hemisphere.

Changes in the Earth's orbit known as the Milankovitch cycle, probably led to greater seasonal temperature variations in the Northern Hemisphere, although global annual means temperatures were probably similar to those of the current Holocene.

The discovery of ancient DNA retrieved from ice 1.2 miles beneath the surface indicates that the ice fields of southern Greenland may be more resilient to rising global temperatures during a warm period 116,000 to 130,000 years -the Eemian interglacial era- when temperatures were 5 degrees higher than today suggests that ice on top of the ancient forest did not melt as believed.

The DNA could have been preserved only if the ice layers remained largely intact. If it had melted, the remains of the ancient trees and insects would have been replaced by new flora and fauna.

"If our data is correct, this means that the southern Greenland ice cap is more stable than previously thought," said Eske Willerslev, research leader and professor of evolutionary biology at the University of Copenhagen whose team's findings are published today in the journal Science. Eske Willerslev, . "This may have implications for how the ice sheets respond to global warming. They may withstand rising temperatures."

The findings run counter to global warming specialists who speculate that Greenland's icefields will melt in the rising temperatures of coming decades predicted by computer models of climate change, with hundreds of trillions of gallons of water flowing into the Atlantic. This could cause ocean levels worldwide to rise anywhere from 3 to 20 feet, according to computer projections -- unsettling news for seaport cities like London, New York, and Boston.

Scientists not involved in the study warn, however, that current climate change is so driven by pollution from power plants, industry, and other human activity that it is nearly impossible to draw a meaningful conclusion about the durability of Greenland's ice.

Posted by Casey Kazan.