This article was published on January 17, 2013, on the Hoover Institution Journal, called Defining Ideas, www.definingideas.org; Charles L. Hooper is president of Objective Insights, a company that consults for pharmaceutical and biotech companies, and is a visiting fellow at the Hoover Institution.
This extract I found most interesting and compelling.
“…consider the significance of the Vikings in Greenland. Erik the Red, the legendary Viking, was exiled from Iceland and sailed to Greenland in 982 AD, where he found birch trees and hills blanketed in green grass. From 985 to 1408, the Vikings had vibrant farming settlements on Greenland. However, if you go there today, you won’t see any farms or even any Viking kids running around; you will see ruins. Why did the Vikings leave Greenland? It turns out that the Viking settlements coincided with the Medieval Warm Period and ended with the Little Ice Age, which caused the Vikings to leave Greenland’s deteriorating fields.
If the Vikings were able to farm Greenland a thousand years ago but would not be able to today, we can assume that the Medieval Warm Period was warmer than the climate today. The scientific studies support this conclusion. Over 120 published studies have formed a conclusion about the Medieval Warm Period: approximately 10 of those studies say it was cooler than today, 20 say it was equal to today, and 90 say it was warmer than today. Of the 110 studies that quantified their results, the conclusion was that the Medieval Warm Period was, on average, about 0.5 degrees Celsius warmer than today.
Withe these results, today’s warm temperatures can be seen in the context of regular, long-term fluctuations of earth’s temperatures. More importantly, these results appear to exonerate carbon dioxide emission. During medieval times, the human population was just 6 percent of its current level and industrialization would not occur for almost a millennium…Something else must be driving changes in the climate because anthropogenic carbon emissions were not a factor when temperatures reached a peak hundreds of years ago.”
The full article is worth reading.