GLOBAL warming crusaders like to say science is “settled” and only members of the Flat Earth Society doubt their theories. But to accept that claim, citizens must ignore centuries of weather data, as was made clear at a recent U.S. House subcommittee hearing.
In recent years, global warming believers have typically described every major weather event — whether drought, ice storm, tornado, or hurricane — as both “unprecedented” and an outcome of man-made climate change. Yet John R. Christy, distinguished professor of Atmospheric Science at the University of Alabama in Huntsville, warned lawmakers such conclusions are largely unsupported, with many claims based on as little as 50 years of data instead of centuries.
Where long-term data is available, it often undermines portrayals of recent weather events as unnaturally extreme. Christy noted “our nation experienced droughts in the 12th century, the so-called megadroughts, which were much worse than any we've seen in the past century.”
A 500-year history of moisture in the upper Colorado River basin actually “indicates the past century was quite moist” compared to other centuries. From 3,000 to 1,500 years ago, Christy noted, the Great Plains were so dry “a significant parabolic sand dune ecosystem developed,” particularly in western Nebraska and northeastern Colorado.
“In other words, parts of the Great Plains resembled a desert,” Christy said. Similar drought reoccurred during Medieval times (900-1300 AD) before the “climate moistened and cooled beginning around 1300 AD to support the shortgrass prairie seen today ...”
In the Antarctic, a reconstruction of 308 years of temperature variations (from 1702-2009) using stable isotopes found a recent warming trend, but also showed “this warming trend is not unique.” More dramatic warming and cooling trends occurred in the mid-19th and 18th centuries.
Roger Pielke Jr., a professor who first began studying extreme weather and climate in 1993 at the National Center for Atmospheric Research in Boulder, Colo., was blunt in his assessment.
“There exists exceedingly little scientific support for claims found in the media and political debate that hurricanes, tornadoes, floods and drought have increased in frequency or intensity on climate time scales either in the United States or globally,” Pielke said. He noted that hurricane landfalls “have not increased in the U.S. in frequency, intensity or normalized damage since at least 1900.”
The same thing is true for tropical cyclones globally since at least 1970. Pielke said floods “have not increased in the U.S. in frequency or intensity since at least 1950,” and tornadoes in the United States “have not increased in frequency, intensity or normalized damage since 1950, and there is some evidence to suggest that they have actually declined.” Droughts have “become shorter, less frequent and cover a smaller portion of the U.S. over the last century.”
Pielke's testimony is notable because he doesn't reject the idea that man-made changes can impact the environment. But he makes clear recent weather events can't be described as unusual by historic standards.
Christy and Pielke's testimony is a useful reminder that skepticism is warranted in the debate over purported man-made climate change, particularly when proposed solutions involve significant, negative impact on the economy and citizens' quality of life. Policies with such negative consequence should be avoided, particularly if they are being advanced in response to events that may be unusual, but not unnatural.