It has often been cited as one of the classic examples of how changes in climate have shaped human history.

Circa the year 985, Erik the Red led 25 ships from Iceland to Greenland, launching a Norse settlement there and giving the vast ice continent the name "Greenland." Within just a few decades, the Norse -- sometimes also dubbed Vikings -- would make it to Newfoundland as well. They maintained settlements of up to a few thousand people in southwest Greenland for several centuries, keeping livestock and hunting seals, building churches whose ruins still stand today, and sending back valuable walrus tusks and other prizes for trade -- until, that is, these settlements were abandoned by the mid-1400s.

Climate change has often been cited as key element to this story -- the basic notion being that the Vikings colonized Greenland in an era dubbed the "Medieval Warm Period," which ran roughly from 950 to 1250, but then were forced to abandon their Greenland settlements as temperatures became harsher in the "Little Ice Age," from about 1300 to 1850.

Yet in a new study published Friday in Science Advances, researchers raise doubts about whether the so-called Medieval Warm Period was really so warm in southern Greenland or nearby Baffin Island -- suggesting that the tale of the Vikings colonizing but then abandoning Greenland due to climatic changes may be too simplistic. Their evidence? New geological data on the extent of glaciers in the region at the time, finding that during the era when the Norse occupied the area, glaciers were almost as far advanced as they were during the subsequent Little Ice Age.

"This study suggests that while the Vikings may have left Iceland when it was relatively warm, they arrived in the Baffin Bay region, and it was relatively cool," said Nicolás Young, a professor at the Lamont-Doherty Earth Observatory at Columbia University and lead author of the study, which was conducted with three colleagues from Columbia and the University at Buffalo. "So for their initial settlement, and the first few centuries when they were there, they persisted and thrived somewhat during a relatively cool climate. And so it's sort of a stretch to say that a cool climate is what drove them out of the region, when they demonstrated that they could be somewhat successful during a cool climate."

The scientists were able to infer this from -- literally -- large piles of rock and mud.

When glaciers advance, you see, they plow up earth and rock and, at their terminus, leave a large debris pile called a "moraine." When glaciers then retreat, the moraine is left behind and provides evidence not only of prior glacier extent but also, if rocks and sediment can be dated, around when the glacier was at that location.

There's a problem, though, with studying moraines to try to make inferences about glaciers during the time when the Norse occupied Greenland. The trick is that glaciers advanced after that period, during the Little Ice Age. And when they advanced, they would also have "bulldozed" prior moraines, in Young's words.

However, Young and his team were able to identify key spots in western Greenland and on Baffin Island where residues from earlier moraines still existed. "We found a few locations where there are slivers of older, pre-Little Ice Age moraines, that are preserved literally just beyond the Little Ice Age moraine," said Young. "I'm talking like meters, you can throw a baseball over to them."

Dating techniques were then used to confirm the age of the rocks that comprised the moraines. Once rocks are no longer beneath glaciers but rather are exposed to the open air, they get bombarded by cosmic rays and so develop more and more of a so-called "cosmogenic nuclide" called beryllium-10 -- thus, by measuring amounts of beryllium-10, their ages can be determined.

The researchers conclude that during the time of the Norse settlements, at least in this region around Baffin Bay and the Labrador Sea, the climate was pretty cool. Granted, conditions may have been warmer in Europe at the time, but the gist is that the so-called "Medieval Warm Period" was, at best, rather inconsistent and regionally varied. That's a conclusion that other studies have also supported -- with some researchers now calling it the "Medieval Climate Anomaly" to try to avoid any confusion, much less the incorrect idea that it was a uniform warm period such as the one in which we currently live.

"There's certainly strong evidence in Europe that that was a real thing," said Young of the "Medieval Warm Period." "But it's certainly not a global event, it was patchy, with quite a bit of variability."

This means that the Norse may not have been either ushered into or chased out of Greenland by temperatures alone. "The implication there is that there's other socioeconomic factors that probably led to the Norse sort of packing up shop and leaving the region," said Young.

"What's novel here is both the new glaciological data from Greenland and the implications that has for the prevailing wisdom about the Norse colonization of Greenland and what it says, or doesn't say, about Medieval climate," said Michael Mann, a climatologist at Penn State University who has published extensively on temperature variations in the North Atlantic region both in the present and in past eras, but was not involved in the study.

In particular, Mann has previously found that while medieval warmth was substantial in some regions, in a global sense it was not uniformly as warm as the planet is now.

All of this does, of course, raise the question of why, if it's not a simple climate change story, the Norse eventually abandoned their Greenland settlements.

Recent research has promoted a more multi-causal understanding of these events, one in which the Vikings of Greenland showed considerable ability to adapt to changing climates and conditions -- including by greatly increasing their dependence on hunting seal -- but also faced a variety of 14th- and 15th-century challenges. Some may have been partly climatic, but at the same time, there were also signs of growing conflict with the Inuit in the region, and also decreasing returns from the trade in walrus tusks and polar bears, thanks to economic shifts back in Europe.

"Conceiving the end of Norse Greenland as a case of maladaptation by an inflexible society in the face of climate change allows neither justice to their innovation nor appropriate lessons to be drawn from that completed experiment," notes a recent study advancing such a multi-causal understanding of the Viking departure.

Similarly, Judith Jesch, who heads the Centre for the Study of the Viking Age at the University of Nottingham in the UK, wrote in a recent book that "The causes of the end of [Norse] Greenland may therefore. . .need to be sought in economic, cultural and demographic factors, and perhaps the breakdown of the social order that maintained the economy."