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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

What the science says...

Greenland's ice sheet is at least 400,000 years old and the warmer climate experienced when the Vikings arrived was not a global phenomenon.

Greenland is a large area situated east of Canada, between the Arctic and Atlantic oceans. About 80% of the island is covered by the Greenland ice sheet. During the 980s, Scandinavian and Icelandic explorers established two or three (according to different accounts) settlements on the south-west coast of Greenland. So what were the conditions in Greenland like 1000 years ago? More precisely, the blog will explore the three following questions:

How old is the ice sheet?

Is there any evidence of global warming at that time?

Are there differences between past and ongoing climate change?

The Greenland ice sheet is at least 400,000 years old

Scientists have estimated that the Greenland ice sheet is between 400,000 and 800,000 years old. This means that the island is unlikely to have been markedly different when Europeans settled there. However, there is evidence that the settled areas were warmer than today, with large birch woodlands providing both timber and fuel. This warmth coincided with the period known as the Medieval Climate Anomaly (more commonly the Medieval Warm Period), which we will discuss below.

So how did Greenland get its name? According to the Icelandic sagas, Erik the Red named it in an attempt to lure settlers in search of land and the promise of a better life. However, the age of the ice sheet, which is more than 3 kilometres thick in places, indicates that the opportunities to establish communities would have been limited to small areas.

Warming was not global during the Medieval Climate Anomaly

During the Medieval Climate Anomaly, some areas, most notably in the North Atlantic, were at least as warm as today, if not warmer. However, other areas were colder, and overall the evidence suggests that global temperatures during this period were similar to those at the beginning or middle of the 20th century. This period is explored in more depth here.

So not only was Greenland mostly covered by ice when Europeans settled there, the relatively warm conditions during this period were not a global phenomenon. This contrasts with what were are seeing today, where warming is truly global. The different cause behind the warming then and now, which we will look at next, further invalidates any attempt to draw parallels between medieval Greenland and today's conditions.

Natural versus man-made climate change

Warming can be the result of a number of factors, which means that the cause of past climate change is not necessarily implicated in current climate change. For instance, the Medieval Warm Period was characterised by relatively high solar activity, low volcanic activity and possible changes in ocean circulation patterns. These factors can explain both the scale and pattern of warming at that time. However, they cannot explain recent warming. More to the point, changes in natural factors would probably have led to slight cooling in the past few decades. This contrasts with the multiple lines of evidence pointing to the role played by humans in recent warming, as illustrated by the figure below.

Conclusion

Greenland is unlikely to have been radically different 1000 years ago since the ice sheet is at least 400,000 years old. Some people have tried to cast doubt on the extent and nature of recent climate change by focusing on narrow areas at specific times. In this instance, they claim that the establishment of Norse settlements around the Medieval Climate Anomaly proves that Greenland was green, inferring that current warming is not exceptional. Yet the evidence shows that not only was Greenland not green, the warmth was mainly a regional phenomenon caused by natural factors. Compare this with the unequivocal finding of the scientific community regarding ongoing warming; climate change now is global and driven primarily by human activities.

Updated on 2012-12-17 by Anne-Marie Blackburn.

Climate Science Glossary

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What the science says...

The Greenland ice sheet is at least 400,000 years old

Warming was not global during the Medieval Climate Anomaly

Natural versus man-made climate change

Conclusion