The Political Science of Climate

Article excerpt


Today the Senate Environment and Public Works Committee, chaired by James Inhofe, Oklahoma Republican, will hold a landmark hearing on recent developments in climate science. This normally arcane field is our most politicized science, thanks to the Kyoto Protocol and related energy policy issues, as will become obvious at Inhofe's hearing.

The proximate matter at hand is the history of global surface temperature for the last 1,000 years. The ultimate issue, though, is how and why the political process distorts the normal business of science for its own ends.

Most atmospheric scientists are taught that the Earth's climate is hardly a stable thing - strong evidence of that being the 5,000 feet of ice over what are now some major North American cities for much of the last 50,000 years. Since the last Big Ice Age ended some 11,000 years ago, surface temperatures continued to jump around.

The largest excursion was from 4,000 to 7,000 years ago, when it was about 1 to 3 degrees (F) warmer than recent decades, which themselves have been above the mean for the last 1,000 years. Before the current era of climate hysteria, textbooks called those millennia the "Climatic Optimum" because they accompanied the rise of agriculture and civilization.

There are literally thousands of refereed scientific papers on the climate of the last millennium, and almost all of them find some evidence for two or three cold centuries ending around 1900, called the "Little Ice Age," and an equivalent warm era, the "Medieval Warm Period" peaking around 900 years ago. This is knowledge so common that some new study comes every few weeks or so finding local evidence (pollen deposits, corals or tree rings) for either age or both periods.

In 1999, Michael Mann, now an assistant professor at the University of Virginia, composited a number of these studies (prior to 1400, a small number: only nine datasets), compared them to observed temperatures in the last 100 years, and traced out an average temperature history back to AD 1000 that destroyed both the Little Ice Age and the Medieval Warm Period.

Removing those makes late 20th-century temperatures anomalous, and Mr. Mann's study is the basis for the oft-repeated claim that recent decades are the "hottest in the last 1,000 years. …