is come from the north, so close to the reefs that none can sail by the old route without risking his life.” [See “Determining the Climate.”]
As the diet and other living conditions of the Vikings deteriorated, which was also the case for other Europeans, the people became more vulnerable to disease. Over a few years up to and including 1349 AD, two-thirds of the entire population of Norway died from the Black Death. The Vikings were struggling just to survive. Major sailing expeditions were no longer an option.
Why has the Earth’s climate changed so dramatically over the past 1,000 years? The answer to that question is well-known but is not widely publicized (and is not normally taught in our schools). The correct explanation is that the amount of sun activity reaching the earth varies considerably over time. Periods of high sun activity, which include explosions of solar radiation called “sun spots,” have the effect of warming the earth. Periods of low sun activity, in contrast, have the effect of cooling the earth. Climate change is primarily caused by changes in sun activity, not by changes in carbon dioxide levels—man-made or otherwise.
The following chart illustrates the extremely high correlation between sun activity and global temperature. As is obvious from the chart, sun activity is the primary cause of temperature change on the earth:
Sun activity correlated to temperature changes