Dr. David Deming
College of Earth and Energy, University of Oklahoma
I had another interesting experience around the time my paper in Science was published. I received an astonishing email from a major researcher in the area of climate change. He said, "We have to get rid of the Medieval Warm Period."
The Medieval Warm Period (MWP) was a time of unusually warm weather that began around 1000 AD and persisted until a cold period known as the "Little Ice Age" took hold in the 14th century. Warmer climate brought a remarkable flowering of prosperity, knowledge, and art to Europe during the High Middle Ages.
The existence of the MWP had been recognized in the scientific literature for decades. But now it was a major embarrassment to those maintaining that the 20th century warming was truly anomalous. It had to be "gotten rid of."
In 1769, Joseph Priestley warned that scientists overly attached to a favorite hypothesis would not hesitate to "warp the whole course of nature." In 1999, Michael Mann and his colleagues published a reconstruction of past temperature in which the MWP simply vanished. This unique estimate became known as the "hockey stick," because of the shape of the temperature graph.
Normally in science, when you have a novel result that appears to overturn previous work, you have to demonstrate why the earlier work was wrong. But the work of Mann and his colleagues was initially accepted uncritically, even though it contradicted the results of more than 100 previous studies. Other researchers have since reaffirmed that the Medieval Warm Period was both warm and global in its extent.
There is an overwhelming bias today in the media regarding the issue of global warming. In the past two years, this bias has bloomed into an irrational hysteria. Every natural disaster that occurs is now linked with global warming, no matter how tenuous or impossible the connection. As a result, the public has become vastly misinformed on this and other environmental issues.
Earth's climate system is complex and poorly understood. But we do know that throughout human history, warmer temperatures have been associated with more stable climates and increased human health and prosperity. Colder temperatures have been correlated with climatic instability, famine, and increased human mortality.
The amount of climatic warming that has taken place in the past 150 years is poorly constrained, and its cause--human or natural--is unknown. There is no sound scientific basis for predicting future climate change with any degree of certainty. If the climate does warm, it is likely to be beneficial to humanity rather than harmful. In my opinion, it would be foolish to establish national energy policy on the basis of misinformation and irrational hysteria.