Letters

Warmer than when?

The article "Sizzling June fires up greenhouse debate" (SN: 7/25/98, p. 52) contained two errors. First, while the 1990s have been the hottest decade since people began systematic temperature measurements in the mid-1800s, it is not the hottest decade on record. Even proponents of the theory of human-caused global warming recognize data indicating Earth has been hotter than it is now many times—most recently around 600 years ago, before the advent of the most recent "little ice age." The current warming trend began as Earth came out of the little ice age—an important fact that is all too often overlooked in the global warming debate.

Second, the Kyoto Protocol is not stalled in any Senate committee, since the Clinton administration has yet to sign it or submit it to the Senate for ratification. The administration recognizes that the treaty has several problems and has vowed not to submit it to the Senate until they are addressed.

H. Sterling Burnett
National Center for Policy Analysis
Dallas, Texas

There is little debate about the statement that the 1990s is the warmest decade on record for global temperatures. Reliable records of global temperatures reach back only into the 19th century. For earlier times, researchers try to gauge temperature trends from a much spottier data set, which can hardly be considered a global record.

More important is the question of whether Earth is now warmer than it was earlier in this millennium. There is evidence that parts of Europe were warm during the so-called Medieval Warm Period, particularly in the 11th and 12th centuries, but it is far from clear whether this was a global phenomenon and whether temperatures during this period were higher or lower than today's. Some parts of the globe did not show any warming back then, whereas other regions warmed up at different times than did Europe.

The Intergovernmental Panel on Climate Change in its 1995 report said that "it is not yet possible to say whether, on a hemispheric scale, temperatures declined from the 11­12th to the 16­17th centuries. Nor, therefore, is it possible to conclude that global temperatures in the Medieval Warm Period were comparable to the warm decades of the late 20th century." The IPCC later said that data from studies of alpine glaciers "suggest that in at least alpine areas, global 20th century temperatures may be warmer than any century since 1000 AD, and perhaps as warm as during any extended period (or several centuries) in the past 10,000 years."

With regard to the Kyoto Protocol, you are correct that the administration has not yet submitted it to the Senate for ratification. —R. Monastersky

No smoking gun

Your news report "Exposure to smoke yields fetal mutations" (SN: 10/3/98, p. 213) omitted mentioning the relevant epidemiology. A Medline search yielded four studies that do not indicate that maternal smoking/passive smoking increases cancer risk among infants.

These studies directly contradict the statement by NCI's Sholom Wacholder that epidemiological findings link prebirth exposure to carcinogens with childhood leukemia. I don't know what studies Wacholder refers to, but they certainly have nothing to do with maternal smoking.

Steven Milloy
Potomac, Md.

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