The Physical Evidence of Earth's Unstoppable 1,500-Year Climate Cycle

Studies | Environment | Global Warming

No. 279
Friday, September 30, 2005
by S. Fred Singer & Dennis T. Avery


Seabed Sediments

Let’s look now at another source that seems to confirm the 1,500-year climate cycle: seabed sediments.

Gerard Bond of Columbia University’s Lamont-Doherty Earth Observatory analyzed sediments on the floor of the southern North Atlantic. Roughly every 1,500 years, there was a surge in the amount of rocky debris picked up by the glaciers as they ground their way across eastern Canada and Greenland. This ice-rafted debris was then floated much farther south before the icebergs melted and it dropped to the sea floor. Both the increase in the volume of the debris and its floating much farther south indicated severe cold periods.

Bond found nine of these cycles in the last 12,000 years, and they matched those in the cores from the Greenland Ice Sheet and the Vostok Antarctic glacier — again strengthening our confidence that the cycles are real and significant.

Bond’s 1997 research report in Science10 begins:

"Glacial rocks deposited in Atlantic seabed sediments show a 1,500-year cycle."

“Evidence from North Atlantic deep-sea cores reveals that abrupt shifts punctuated what is conventionally thought to have been a relatively stable Holocene [interglacial] climate. During each of these episodes, cool, ice-bearing waters from north of Iceland were advected as far south as the latitude of Britain. At about the same times, the atmospheric circulation above Greenland changed abruptly. . . . Together, they make up a series of climatic shifts with a cyclicity close to 1,470 years (plus or minus 500 years). The Holocene events, therefore, appear to be the most recent manifestation of a pervasive millennial-scale climatic cycle operating independently of the glacial-interglacial climate state.” (emphasis added)

Bond thus points up the fact that the moderate 1,500-year cycle is powerful enough to periodically warm the Earth’s climate even when thousands of trillions of tons of ice are determined to keep it Ice-Age cold, and to periodically chill the planet even during warm interglacial periods.

The evidence for this moderate but persistent climate cycle has continued to mount around the world in recent decades.

Peter deMenocal’s team found African coastal seabed sediments documented a history of major changes in sea surface temperatures.11

Changes in plankton numbers and species gave the deMenocal team ocean temperature readings from the past, and the amounts of dust blown from Africa were an indicator of drought. These proxies tell us that when the sea surface temperatures fell off West Africa, much of the continent went drier for centuries. Then, the climate snapped back, quickly bringing such heavy rains that large lakes formed in the Sahara Desert. The most recent cooling in the region was a two-stage Little Ice Age between 1300 and 1850, essentially simultaneously with similar coolings in the Greenland ice cores, in the seabed sediments of the North Atlantic found by Bond, and in the reconstructed sea surface temperatures of the Sargasso Sea found by Lloyd Keigwin.12

Bond concluded that every 1,500 years, harsh cold periods drop North Atlantic ocean temperatures by 2 to 3.5° C. However, deMenocal says ocean temperatures off Africa simultaneously dropped even more sharply, with changes of 3 to 4° C.

Bond’s subsequent study demonstrated the linkage between the Earth’s warming-cooling cycle and the sun, using carbon-14 and beryllium-10 as proxies for solar warming and cooling.13

He wrote, “It is highly unlikely that Holocene climate forcing alone could have produced such large and abrupt production-rate changes at essentially the same time in both [the C-14 and Be-10]. Our correlations are evidence, therefore, that over the last 12,000 yearsvirtually every centennial time scale increase in drift ice documented in our North Atlantic records was tied to a distinct interval of . . . reduced solar output.

“A solar influence on climate of the magnitude and consistency implied by our evidence could not have been confined to the North Atlantic....”

"The 1,500-year cycle has persisted more than one million years."

Dating Back a Million Years. Near Iceland, Maureen Raymo of Boston College found the Earth was undergoing Dansgaard-Oeschger’s 1,500-year climate cycles more than a million years ago. Raymo and her research team retrieved a very long sediment core from the deep sea bottom south of Iceland. As the Raymo team wrote in Nature:

“Here we use sediment records of past iceberg discharge and deep-water chemistry to show that such millennial-scale oscillations in climate occurred over one million years ago.... Our results suggest that such climate instability may be a pervasive and long-term characteristic of Earth’s climate....”14

A Global Sampling of Sea Bed Cores. South of Iceland, Giancarlo Bianchi and Nicholas McCave studied a 1,500-year climate cycle that “may be related to an internal oscillation of the climate system.” The grain sizes of sediments carried by the Iceland-Scotland part of the “Atlantic ocean conveyor” reveal the strength of the current. Colder periods with less ice melt generate slower bottom currents that carried smaller sediment grains; warmer periods with stronger currents carried larger sediment grains. They found that flows changed with the Medieval Warming and the Little Ice Age, “and extend over the entire Holocene epoch with a quasi-periodicity of ~1500 years.”15 (emphasis added)

In the Norwegian Sea, Sweden’s Carin Andersson led a team which constructed a 3,000-year temperature history from the stable isotopes in the plankton and the number and types of protozoan skeletons from seabed sediment cores.16 The climate history shows a long cold period before the Roman Warming, then the Dark Ages, the Medieval Warming and the Little Ice Age.

A Baltic Sea sediment core shows a cold-weather period beginning about 1200, characterized by “a major decrease in the [algae cyst] assemblage and an increase in cold water [algae species].”17 The study also found the present Baltic is still too cold to support the subtropical marine species it had during the Medieval Warming.

Off Alaska, Old Dominion University’s Dennis Darby analyzed sediments from the continental shelf.18 The number and species of dinocysts (tiny ”cocoons” left behind by one-celled organisms) gives evidence of sea surface temperatures and sea-ice cover. The most surprising result of this study was the large variation in Arctic temperatures shown by the proxies — 6° C over the last 8,000 years, a greater range than on the Greenland Ice Sheet.

"Abrupt climate changes can occur within a decade."

In the eastern Mediterranean, sediments accumulate rapidly and yield highly accurate seabed cores. Bettina Schilman from the Geological Survey of Israel used such proxies as oxygen-18 and carbon-13 isotopes in phytoplankton, titanium/aluminum ratios, iron/aluminum ratios, magnetic susceptibility, and color index to analyze past climates.19 She says abrupt climatic events occurred 270 years ago and 800 years ago that “probably correlate” with the Little Ice Age and the Medieval Warming. She also notes corroborating evidence of the Medieval Warming in high Saharan lake levels,20, 21 and high levels in the Dead Sea,22, 23, 24, 25 and the Sea of Galilee,26, 27 as well as a precipitation maximum at the Nile headwaters.28, 29

In the Arabian Sea, west of Karachi, Pakistan, two seabed sediment cores date back nearly 5,000 years, and show “the 1,470-year cycle previously reported from the glacial-age Greenland ice record.” W. H. Berger and Ulrich von Rad suggested the cycles were tide-driven. However, they also note that “internal oscillations of the climate system cannot produce them.30 (emphasis added)

Near the Philippines, the productivity of the phytoplankton is closely related to the strength of the winter monsoon. The production of phytoplankton was larger during glacial periods than during interglacial periods, but the researchers found that “the 1,500-year cycle...seems to be a pervasive feature of the monsoon climatic system.”31

Off the northern tip of the Antarctic Peninsula, Boo-Keun Khim of Seoul University found the Little Ice Age and Medieval Warming, along with earlier warming/cooling cycles.32 Khim also notes that evidence of the Little Ice Age has been found in several other studies of Antarctic marine sediments, including Leventer and Dunbar, who reported on their study of algae microfossils at Antarctica’s McMurdo Sound in 1988.33


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