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Trouble in Paradise
Volume 5, Number 11: 13 March 2002

A couple years back, Linsley et al. (2000) published a paper in Science in which they described how they reconstructed a 271-year history of sea surface temperature (SST) for the central gyre of the subtropical South Pacific Ocean based on strontium/calcium (Sr/Ca) ratios derived from a core of material extracted from a massive colony of Porites corals on the southwest side of Rarotonga in the Cook Islands (21.5S, 159.5W). That exercise revealed the existence of a period of approximately 30 years' length centered on about the year 1745 when SSTs in that part of the world were at least 1.5C warmer than they were at the end of the 20th century.

In reviewing Linsley et al.'s results shortly after their publication, we commented on the fact that this astounding 18th century South Pacific warmth was a radical departure from the vastly colder conditions implied for that time period by the infamous Northern Hemispheric "hockey stick" temperature history of Mann et al. (1999), which portrays the last two decades of the 20th century as the warmest of the past millennium; and we noted that "it would seem only prudent, therefore, to delay judgment on this important matter [i.e., the question of the true temperature history of the whole earth] until more long-term coral-derived temperature data are acquired." Hence, with the recent publication of the second of such data sets from another part of the tropical South Pacific Ocean, we take up the question again.

The study to which we refer - which was also published in Science - is that of Hendy et al. (2002), who reconstructed an even longer 420-year SST history based on similar Sr/Ca measurements of several coral cores taken from massive Porites colonies in the central portion of Australia's Great Barrier Reef, the locations of which cores ranged in latitude from 17.8 to 18.8S and in longitude from 146.1 to 147.1E.

The earliest portion of this region's reconstructed temperature history, from 1565 to about 1700, corresponds to the coldest period of the Little Ice Age as recorded in the Northern Hemisphere [see Earth's Climate History: The Last 1,000 Years in our Subject Index for the original IPCC version of this history (Houghton et al., 1990), as well as the revisionist "hockey stick" temperature history of Mann et al.]. Five-year blocks of mean SSTs during this South Pacific cold period were sometimes 0.5 to 1.0C or more below the region's long-term mean. Over the following century, however, South Pacific SSTs were much warmer, as were temperatures in the Northern Hemisphere, at least according to the original IPCC temperature history, which we believe to be considerably more realistic than the reconstruction of Mann et al. In the South Pacific, in fact, SSTs during this period were consistently as warm as - and many times even warmer than - those of the early 1980s, where the coral record ended. Then, during the late 1800s, the South Pacific once again experienced colder conditions that coincided with the "last gasp" of the Little Ice Age in the Northern Hemisphere, after which the Modern Warm Period made its presence felt in both regions.

These observations do two important things. First, the largely synchronous temperature trends of the South Pacific Ocean and Northern Hemisphere lend credence to our belief that the Little Ice Age was a truly global phenomenon and not - as climate alarmists are prone to claim - a minor regional anomaly of lands bordering on the North Atlantic Ocean. Second, the fact that the data of Hendy et al., as well as the data of Linsley et al., portray mid-18th century South Pacific SSTs as being equally as warm as - or even warmer than - the latter part of the 20th century lends credence to our belief that the climate of the modern world is in no way unusual.

Enlarging on this thought, we note that the mid-18th century warmth of the tropical/subtropical South Pacific Ocean occurs at essentially the same time as the significant peak in Northern Hemispheric temperature that is strikingly evident in the data of Jones et al. (1998), which are reproduced in the paper of Hendy et al. This observation suggests to us that if the data of Hendy et al. and Linsley et al. are representative of the great expanse of Southern Hemispheric ocean, the mid-18th century mean temperature of the entire globe may well have been about the same as it is now.

If true - and there is nothing standing in the way of marine scientists proving or disproving this hypothesis than the conducting of more coral-based paleoclimate studies throughout the Southern Hemisphere - this observation would likely spell the end of the CO2-induced global warming hysteria, which is so ardently propagated by climate alarmists. As can be verified by visiting Carbon Dioxide (History - The Last 1,000 Years) in our Subject Index, for example, the atmosphere's CO2 concentration during this period of potentially equal-to-present warmth was only about 280 ppm, i.e., the baseline value that had prevailed for several centuries prior to the Industrial Revolution. And if the planet could be as warm in the mid-18th century as it is now, especially with so much less CO2 in the air during that earlier time period than there is now, there is no valid basis for claiming that today's warmth is due to the increase in atmospheric CO2 concentration experienced in the interim.

In light of these observations, we urge all who have the capacity to encourage and/or conduct such crucial research to do so as swiftly as possible. As Cane and Evans (2000) have noted with respect to the study of Linsley et al., "their temperature record is persuasive" and "more records of this length and quality would go a long way toward clarifying our picture of the modes of decadal variability." They would also go a long way toward helping to settle the greatest environmental question ever to plague mankind.

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

Cane, M.A. and Evans, M. 2000. Do the tropics rule? Science 290: 1107-1108.

Hendy, E.J., Gagan, M.K., Alibert, C.A., McCulloch, M.T., Lough, J.M. and Isdale, P.J. 2002. Abrupt decrease in tropical Pacific sea surface salinity at end of Little Ice Age. Science 295: 1511-1514.

Houghton, J.T., Jenkins, G.J. and Ephraums, J.J. (Eds.) 1990. Climate Change: The IPCC Scientific Assessment. Cambridge University Press, Cambridge, UK.

Jones, P.D., Briffa, K.R., Barnett, T.P. and Tett, S.F.B. 1998. High-resolution palaeoclimatic records for the last millennium: interpretation, integration and comparison with general circulation model control-run temperatures. The Holocene 8: 455-471.

Linsley, B.K., Wellington, G.M. and Schrag, D.P. 2000. Decadal sea surface temperature variability in the subtropical South Pacific from 1726 to 1997 A.D. Science 290: 1145-1148.

Mann, M.E., Bradley, R.S. and Hughes, M.K. 1999. Northern Hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations. Geophysical Research Letters 26: 759-762.