- The Washington Times - Monday, July 28, 2003

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.” This is climate science in the form of political dynamite, and even has some Republicans tilting toward legislating down our use of fossil fuel (which can only be accomplished by raising the price).

In response, two Harvard scientists, Willie Soon and Sallie Baliunas, along with three other coauthors, inspected a much larger set of the paleo-climatic indicators than Mr. Mann used and concluded (not surprisingly, given the voluminous science literature on this subject) that the cold and warm periods were indeed real and that the climate of the 20th century, while warm, isn’t on some unprecedented excursion.

Despite the mountain of evidence to the contrary, now summarized by the Harvard researchers, the latest compendium on climate science by the United Nations or the Bush administration’s 2001 “Climate Action Report” (based upon the Clinton administrations “National Assessment” of climate change) both gave the distinct impression that Mr. Mann’s work is the definitive synthesis of the climate of the last millennium. In reality, it’s just another step down the research road, an interesting one, but certainly not a final one.

A partial reconciliation is possible. Because there are so few actual climate histories in the early years of the Mann history, the error bars are huge and in fact can accommodate a big Medieval Warm Period. (President Clinton’s “National Assessment” was such an egregious abuse of science that it simply removed Mr. Mann’s error bars). However, for the recent centuries, there are hundreds of scientific papers citing evidence for the Little Ice Age, a preponderance of evidence that is difficult to destroy with one calculation.

It’s not my place to say who is right or who is wrong about the last 1,000 years, and dissonance is what makes science interesting. Nonetheless, the U.N. and the federal science establishment tipped their agendas with inordinate attention to the Mann history, given all of the other evidence. It is to be hoped that at Mr. Inhofe’s hearing, which will feature three of the principal scientists involved, we will find out why and how this happened.

Patrick J. Michaels is senior fellow in environmental studies at the Cato Institute and professor of environmental sciences at the University of Virginia.

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