Charles L. Hooper:
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.
With 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 emissions. During medieval times, the human population was just six percent of its current level and industrialization would not occur for almost a millennium. Sure, there was some clearing of forests and burning of wood, but those actions did not alter the carbon emissions needle, and the level of atmospheric carbon dioxide was low, unlike today, when it is higher than at any time during the past 800,000 years. And yet, somehow, the temperatures during the Medieval Warm Period were warmer than they are today. 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.