110,000 to 12,000 years ago
The cool temperatures of the Quaternary may have allowed our brains to become much larger than those of our of hominid ancestors. While that’s still open to debate, it’s plausible that the most recent glacial period left its mark on our species.
Neanderthals, with whom we shared the planet until just before the last glacial maximum, 20,000 years ago, may have struggled to survive as the rising and falling ice ate away at their habitat – although many other explanations for their extinction have been suggested. What is beyond doubt is that Homo sapiens survived and turned to farmingsoon after the ice retreated, setting the stage for the rise of modern civilisation.
As the glacial period drew to a close and temperatures began to rise, there were two final cold snaps. First, the chilly “Older Dryas” of 14,700 to 13,400 years ago transformed most of Europe from forest to tundra, like modern-day Siberia. After a brief respite, the Younger Dryas, between 12,800 to 11,500 years ago, froze Europe solid within a matter of months – probably as a result of meltwater from retreating glaciers shutting down the Atlantic Ocean’s “conveyor-belt” current, although a cometary impact has also been blamed.
Twelve thousand years ago, the great ice sheets retreated at the beginning of the latest interglacial – the Flandrian – allowing humans to return to northern latitudes. This period has been relatively warm, and the climate relatively stable, although it has been slightly colder than the last interglacial, the Eemian, and sea levels are currently at least 3 metres lower – differences that are being closely scrutinised by researchers keen to understand how our climate will develop.
But this respite from the ice is likely to prove short-lived, at least in geological terms. Human effects on the climate notwithstanding, the cycle will continue to turn, the hothouse period will some day come to an end – and the ice sheets will descend again.
The Coming and Going of Glaciers A New Alpine Melt Theory
May 23, 2005
The Alpine glaciers are shrinking, that much we know. But new research suggests that in the time of the Roman Empire, they were smaller than today. And 7,000 years ago they probably weren't around at all.
A group of climatologists have come up with a controversial new theory on how the Alps must have looked over the ages.
The Morteratsch glacier in Switzerland has retreated by 1.5 km since 1900. Some scientists believe that glacial fluctuation could be a more normal development than previously thought.
He may not look like a revolutionary, but Ulrich Joerin, a wiry Swiss scientist in his late twenties, is part of a small group of climatologists who are in the process of radically changing the image of the Swiss mountain world. He and a colleague are standing in front of the Tschierva Glacier in Engadin, Switzerland at 2,200 meters (7,217 feet). "A few thousand years ago, there were no glaciers here at all," he says. "Back then we would have been standing in the middle of a forest." He digs into the ground with his mountain boot until something dark appears: an old tree trunk, covered in ice, polished by water and almost black with humidity. "And here is the proof," says Joerin.
