Noren, A.J., Bierman, P.R., Steig, E.J., Lini, A. and Southon, J. 2002. Millennial-scale storminess variability in the northeastern Unites States during the Holocene epoch. Nature 419: 821-824.
Climate alarmists loudly proclaim that anthropogenic emissions of atmospheric greenhouse gases may lead to increases in the frequency of severe storms. Hence, there is a tendency for the general public, including the media, to wonder if humanity is to blame for periodic occurrences of extreme weather; while radical environmentalists make no bones about it, claiming we are indeed responsible. But are we?
To correctly answer this question, it is necessary to know where we currently reside in the suite of natural cycles that characterize earth's climate; for as the authors of this important study describe the situation, "the existence of natural variability in storminess confounds reliable detection of anthropogenic effects." This being the case, it was their intention to provide an historical context for addressing this question.
What was done
Sediment cores were extracted from thirteen small lakes distributed across a 20,000-km2 region in Vermont and eastern New York, after which several techniques were used to identify and date terrigenous in-wash layers that depict the frequency of storm-related floods.
What was learned
The authors' data indicate that "the frequency of storm-related floods in the northeastern United States has varied in regular cycles during the past 13,000 years (13 kyr), with a characteristic period of about 3 kyr." There were four major storminess peaks during this period; they occurred approximately 2.6, 5.8, 9.1 and 11.9 kyr ago, with the most recent upswing in storminess beginning "at about 600 yr BP [Before Present], coincident with the beginning of the Little Ice Age."
The authors say that the pattern they observed "is consistent with long-term changes in the average sign of the Arctic Oscillation [AO], suggesting that modulation of this dominant atmospheric mode may account for a significant fraction of Holocene climate variability in North America and Europe." They also note that several "independent records of storminess and flooding from around the North Atlantic show maxima that correspond to those that characterize our lake records [Brown et al., 1999; Knox, 1999; Lamb, 1979; Liu and Fearn, 2000; Zong and Tooley, 1999]."
The authors also report that "during the past ~600 yr, New England storminess appears to have been increasing naturally [our italics]," and they suggest that "changes in the AO, perhaps modulated by solar forcing, may explain a significant portion of Holocene climate variability in the North Atlantic region." They further state that their explanation is appealing "because it makes a specific prediction that New England storminess should be at its greatest when Europe is cold (characteristic of the low-phase AO)," such as during Little Ice Age conditions; and they report that "comparison of our results with the other climate records [cited below], including European glacier fluctuations, suggest that, as predicted, intense storms in New England tend to occur more frequently during periods that are cooler than average in Europe [Mayewski et al., 1994; O'Brien et al., 1995; Holmes et al., 2001; Karlen and Kuylenstierna, 1996; Matthews et al., 2000]."
What it means
This study indicates that: (1) climate fluctuates significantly on a millennial timescale in a reasonably well-defined oscillatory fashion that is independent of the atmosphere's CO2 concentration but is "perhaps modulated by solar forcing," as we and a host of others have long suggested [see Climate Oscillations and Solar Effects (Climate) in our Subject Index], and (2) relatively colder climates are typically characterized by relatively stormier weather, as we also have long suggested [see Extreme Weather in our Subject Index]. The first of these observations tends to discredit the climate-alarmist claim that recent global warming is CO2-induced, in that the warming of the last century or so is but a normal part of earth's naturally-recurring millennial-scale climatic oscillation; while the second observation tends to discredit the climate-alarmist claim that global warming will lead to increases in storminess, in that increases in real-world storminess are typically associated with global cooling.
Brown, P., Kennett, J.P. and Ingram, B.L. 1999. Marine evidence for episodic Holocene megafloods in North America and the northern Gulf of Mexico. Paleoceanography 14: 498-510.
Hormes, A., Muller, B.U. and Schluchter, C. 2001. The Alps with little ice: evidence for eight Holocene phases of reduced glacier extent in the Central Swiss Alps. The Holocene 11: 255-265.
Karlen, W. and Kuylenstierna, J. 1996. On solar forcing of Holocene climate: evidence from Scandinavia. The Holocene 6: 359-365.
Knox, J.C. 1999. Sensitivity of modern and Holocene floods to climate change. Quaternary Science Reviews 19: 439-457.
Lamb, H.H. 1979. Variation and changes in the wind and ocean circulation: the Little Ice Age in the northeast Atlantic. Quaternary Research 11: 1-20.
Liu, K.b. and Fearn, M.L. 2000. Reconstruction of prehistoric landfall frequencies of catastrophic hurricanes in northwestern Florida from lake sediment records. Quaternary Research 54: 238-245.
Matthews, J.A., Dahl, S.O., Nesje, A., Berrisford, M. and Andersson, C. 2000. Holocene glacier variations in central Jotunheimen, southern Norway based on distal glaciolacustrine sediment cores. Quaternary Science Reviews 19: 1625-1647.
Mayewski, P.A., Meeker, L.D., Whitlow, S., Twickler, M.S., Morrison, M.C., Bloomfield, P., Bond, G.C., Alley, R.B., Gow, A.J., Grootes, P.M., Meese, D.A., Ram, M., Taylor, K.C. and Wumkes, W. 1994. Changes in atmospheric circulation and ocean ice cover over the North Atlantic during the last 41,000 years. Science 263: 1747-1751.
O'Brien, S.R., Mayewski, P.A., Meeker, L.D., Meese, D.A., Twickler, M.S. and Whitlow, S.E. 1995. Complexity of Holocene climate as reconstructed from a Greenland ice core. Science 270: 1962-1964.
Zong, Y. and Tooley, M.J. 1999. Evidence of mid-Holocene storm-surge deposits from Morecambe Bay, northwest England: A biostratigraphical approach. Quaternary International 55: 43-50.
Reviewed 20 November 2002