The Medieval Warm Period (MWP) was warmer than today, as evidenced by the fact that the Vikings were able to cross the north Atlantic and settle in Iceland and Greenland due to the reduced ice cover. This is proof that global temperature changes are natural, and that current warming is nothing to worry about.
Fact:
The MWP (900-1150 AD) was not warmer than today, although in northern Europe and the North Atlantic temperatures were similar to today’s. In some parts of the world, however, temperatures actually got colder during the MWP. Scientists estimate that on average, global temperatures were similar to those in the mid-20th century. Interestingly, sea levels then were nowhere near as high as they are today. (They rose by 24 cm over a period of 400 years but never got to 20th century levels.)
If we only look at the natural factors that generated the MWP (changes in solar and volcanic activity, changes in oceanic currents and small changes in the Earth’s orbit), there should have been global cooling over the past 50 years, not warming. Yet we are experiencing the opposite.
The current warming trend is unprecedented – 1.2°C in just over a century. We have not seen such rapid warming in the past two million years, and maybe not for 55 million years. During thaws from ice ages, it took between 1,000 and 2,000 years for the atmosphere to warm by 1°C.
It should also be noted that while the MWP improved living conditions in places like Greenland, it devastated regions like the southwest of the United States, which experienced severe and prolonged droughts. Communities in the latter regions were forced to move, while the Vikings were forced to abandon Greenland when the MWP ended. [Had the Vikings discarded their European farming practices and adopted the Inuit lifestyle, they would not have had to leave Greenland.]
A final point of interest is that Iceland was settled before the Medieval Warm period began – evidence that reduced ice cover was not the reason the Vikings were able to cross the North Atlantic.