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Why We All Love Wally Broecker
Volume 4, Number 46: 14 November 2001

In a paper entitled "Glaciers that speak in tongues and other tales of global warming," which was published in the October 2001 issue of Natural History, Wallace S. Broecker of Columbia University's Lamont-Doherty Earth Observatory describes some scientific findings that are of the utmost importance to our understanding of current and future world climate, findings about which he is intensely concerned but which many other believers in CO2-induced global warming, i.e., those we call climate alarmists, would just as soon ignore.

Broecker begins by discussing the Little Ice Age, a period he refers to as "a cold episode that ran from about 1300 to 1860." He notes that glacial evidence for this significant climatic excursion can be found all the way from the Swiss Alps in the Northern Hemisphere to the Southern Alps of New Zealand's South Island. Furthermore, and in contradiction of the claim of a group of climate revisionists who are trying to convince the world that the Little Ice Age was but an ill-defined regional phenomenon confined to countries around the North Atlantic Ocean, he rightly proffers the opinion (see Little Ice Age in our Subject Index) that "the Little Ice Age cooled not just Europe but the world."

Since 1860, however, the earth has warmed. Yet, as Broecker notes, "roughly half the overall warming since 1860 occurred before carbon dioxide (CO2) emissions from human activities had reached significant levels." Continuing, he says that some people, such as us, "take this as evidence that most of the current upswing in temperature is merely a continuation of the natural events that brought the Little Ice Age to a close." Since this hypothesis is a very real possibility that would be both foolish and dangerous to ignore, he courageously concludes that "we need to know how much earth's temperatures would have fluctuated in the absence of the Industrial Revolution and whether we are now exacerbating or counteracting these fluctuations."

Broecker's first focus in attempting to answer this question is on mountain glaciers, studies of which can allow the reconstruction of past temperatures with a margin of error that is often less than a quarter of a degree C. From a vast array of evidence - including historical records of glacier terminus positions, the size and location of glacial terminal moraines, and the nature of the debris within them - he concludes that several times prior to the glacial expansion of the Little Ice Age, "Alpine glaciers pushed out to roughly the same position they occupied in 1850."

Even more important may be the characteristics of ancient pieces of wood and peat that regularly wash out from beneath retreating glaciers. The carbon dates of these materials fall into distinct groupings, with each group, in the words of Broecker, "presumably representing a warm episode when Alpine glaciers were even smaller than they are today." The most recent of such episodes, of course, would be the Medieval Warm Period (another climatic phenomenon the climate alarmists are wroth to recognize) and before that the Roman Warm Period. [For still others see McDermott et al. (2001).] The existence of these numerous warm periods, which reduced glaciers to even smaller dimensions than they possess today, adds even more evidence to the argument that the current climatic state of the planet is in no way unusual ... and surely not unprecedented!

Other evidence for regularly-recurring "little" warm and cold periods comes from the bottom of the sea, specifically, from sediments that lie beneath the deep waters of the North Atlantic Ocean. There, Broecker's Columbia University colleague Gerard Bond discovered ice-rafted debris, the chemical characteristics of which tell a story of alternating warm and cold periods that have occurred "virtually unchanged, in both amplitude and duration," with a "nearly regular, 1,500-year cycle" that monotonously repeats itself through both ice-age and non-ice-age periods alike.

With such proven and dependable regularity, it's a good bet that this warm/cool climatic cycle - of which the Medieval Warm Period and Little Ice Age are the most recent manifestations - will not be terminating anytime soon. Hence, we feel confident in predicting continued modest warming, based not on the ongoing rise in the air's CO2 content, but on a continuation of the natural 1500-year cyclical rhythm of earth's climate that has operated as far back in time as we have sufficiently-time-resolved data to detect (see our Journal Reviews of the papers by Oppo et al., 1998; Raymo et al., 1998; Bianchi and McCave, 1999; McManus et al., 1999; Keigwin and Boyle, 2000).

Clearly, to repeat some of the concluding words of Broecker, "we can state with some confidence that natural Holocene temperature fluctuations have been on the same scale as the human-caused effects estimated to result from greenhouse gases." Hence, as he continues, "we cannot assume that in the absence of human intervention, earth's temperatures would have remained stable." It would thus appear to be our common conclusion that we cannot unequivocally attribute any of the temperature rise of the past century and a half to CO2-induced global warming. And that is why, as Broecker states in an earlier paper (Broecker, 1999), there exists "adequate room for maneuvering ... for those who doubt that the buildup of carbon dioxide and other greenhouse gases constitutes a substantial threat."

Yes, there is absolutely no way for proponents of CO2 emission regulations to prove their case, especially when all indications suggest that nothing climatically out of the ordinary is even on the verge of happening, or, as climate alarmists are irrationally wont to claim, has already happened. But "does this mean we can all sit back, do nothing, and wait for the results to roll in?" Broecker answers his rhetorical question with a Certainly not. We, however, say Yes, especially with respect to committing the nations of the earth to mandatory CO2 emissions reductions.

With respect to this difference of opinions, it is important to note that they are just that, opinions. Broecker bases his on a belief in the adequacy of current climate models. We base ours on a belief in their inadequacy, as well as the weight of evidence discussed above, plus the likelihood we will need all the atmospheric CO2 we can muster in the years ahead to prevent the catastrophic shortages of food and water that will otherwise likely materialize (see our Editorials of 1 October 1999, 1 February 2000, 15 November 2000, 21 February 2001, 2 May 2001, 13 June 2001).

Although we thus disagree with Broecker on what he thinks we should be doing about the ongoing rise in the air's CO2 content, we have not the slightest doubt about the sincerity of his expressed belief. And we have nothing but the greatest admiration for his scientific insight and integrity. If everyone on both sides of the issue were as forthcoming as he is with respect to these matters, it would be a far, far better world.

Keep up the good work, Wally. We love you!

Dr. Sherwood B. Idso
President
Dr. Keith E. Idso
Vice President

PS: Neither of us has ever met the eminent scientist whose ideas we here discuss, and we hope that our editorial brings him no embarrassment. Clearly it shouldn't, for his life's work is of such a caliber that it can be neither enhanced nor diminished by anything we might possibly say.

References
Bianchi, G.G. and McCave, I.N. 1999. Holocene periodicity in North Atlantic climate and deep-ocean flow south of Iceland. Nature 397: 515-517.

Broecker, W. 1999. Climate change prediction. Science 283: 179.

Broecker, W.S. 2001. Glaciers That Speak in Tongues and other tales of global warming. Natural History 110 (8): 60-69.

Keigwin, L.D. and Boyle, E.A. 2000. Detecting Holocene changes in thermohaline circulation. Proceedings of the National Academy of Sciences USA 97: 1343-1346.

McDermott, F., Mattey, D.P. and Hawkesworth, C. 2001. Centennial-scale Holocene climate variability revealed by a high-resolution speleothem 18O record from SW Ireland. Science 294: 1328-1331.

McManus, J.F., Oppo, D.W. and Cullen, J.L. 1999. A 0.5-million-year record of millennial-scale climate variability in the North Atlantic. Science 283: 971-974.

Oppo, D.W., McManus, J.F. and Cullen, J.L. 1998. Abrupt climate events 500,000 to 340,000 years ago: Evidence from subpolar North Atlantic sediments. Science 279: 1335-1338.

Raymo, M.E., Ganley, K., Carter, S., Oppo, D.W. and McManus, J. 1998. Millennial-scale climate instability during the early Pleistocene epoch. Nature 392: 699-702.