For Immediate Release:
Contact: Candace Crandall
Tel: (703) 503-5064
e-mail: Crandall@SEPP.org

FAIRFAX, VA, JUNE 25, 1997---Over the course of the last 3,000 years, the Earth's climate has undergone large and abrupt temperature fluctuations, with no drastic effects on human populations, according to atmospheric physicist Dr. S. Fred Singer, former director of the U.S. Weather Satellite Service and now president of The Science & Environmental Policy Project.

Speaking on Friday, June 20th, before an enthusiastic, standing-room-only audience of students and faculty at the University of South Florida's Marine Sciences Department in St. Petersburg, Singer gave a one-hour presentation on recent climate change research, highlighting, among other findings, two elements considered key to the global warming debate:

1. The global climate record, especially the impact of rapid change in temperature. Officials with the UN Intergovernmental Panel on Climate Change claim that a human-induced greenhouse warming could lead to temperature changes that are greater and/or faster than anything experienced previously. A recent analysis of ocean sediment cores from the Sargasso Sea, where sedimentation rate is so high that one can distinguish time variations as short as a decade, gives a different picture.

This analysis, by scientists from the Woods Hole Oceanographic Institution in Massachusetts and published by L.D. Keigwin in Science (Vol 274, pp. 1504-1508, 1996), plots sea surface temperature (which closely tracks atmospheric temperature) in narrow time bands over the last 3,000 years. It shows rapid and repeated changes, as much as 2 degrees C, sometimes over just a few decades. Other studies, using tree ring data (for example, G.C. Jacoby in Science, Vol. 273, pp. 771-773, 1996) generally confirm the ocean core results.

2. The carbon dioxide (CO2) record. A scientific review of measurements done by a number of investigators, and published by R.A. Berner in Science (Vol. 276, pp. 544-545, 1997), shows that 500 million years ago atmospheric CO2 was some 20 times higher than present values. It dropped, then rose again some 200 million years ago to 4-5 times present levels--a period that saw the rise of giant fern forests--and then continued a slow decline until recent pre-industrial time.

We don't know to what extent climate is affected by CO2 concentration, said Singer. Historical records document a period of much colder temperatures--the "Little Ice Age," between 1450 and 1850--and a period of warmer temperatures--the "Medieval Climate Optimum," around the year 1000. Rapid temperature variations were found also during the most recent ice age, when the atmospheric CO2 concentration was only about 200 parts per million (ppm), less than the 280 ppm pre-industrial value. The cause of such natural variations is largely unknown.

Observations indicate that, contrary to IPCC claims, the Earth has already undergone climate changes, even in recent history, that exceed feared future changes based on computer models. Perhaps more important, at least from a policy standpoint, the climate record gives no guidance as to what constitutes a "dangerous" atmospheric level of carbon dioxide, the avoidance of which is the announced purpose of the Global Climate Treaty.

Singer's talk a the University of South Florida was the latest in a series of global warming seminars given at the invitation of academic and scientific groups. In the last year, Singer has lectured at Oxford University (Great Britain), University of Bologna (Italy), Stanford, SUNY-Stony Brook, California Institute of Technology, UC-San Diego, Washington College (Maryland), Brookhaven National Laboratory, at the National Oceanographic and Atmospheric Administration, and at conferences of the American Geophysical Union and the National Aeronautics and Space Administration, among others. This week, he also spoke in Washington, D.C., at a conference of the Public Relations Society of America.

The Science & Environmental Policy Project, a non-profit, policy research group based in Fairfax, Virginia, was founded in 1992 to foster greater reliance on sound science in decisions affecting health and environment. For a printed copy of this press release, with graphs from the studies mentioned, fax SEPP at (703) 352- 7535.

Figure 1 Detailed temperature variations of the past 3,000 years, as determined from ocean sediment studies. Note the rapid variations, as well as the much warmer temperatures that existed 2.500 years ago.

Figure 2 Historical Record of Atmospheric Carbon Dioxide concentration, based on a collection of measurements. The concentration was about 20 times the pre-industrial value [of 280 ppmv] 500 million years ago. It dropped to very low levels as chemical weathering removed CO2 from the atmosphere. It reached a secondary peak around 200 million years ago and has been declining every since. The anthropogenic increase from the burning of fossil fuel is likely to increase the atmospheric concentration for no more than 2 or 3 centuries.

Figure 3 The climate record as deduced from the width of tree rings. Compared are the ring-width chronology (solid line) and the reconstruction of Arctic annual temperature anomalies (dashed line).