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Holocene Climate Variability
Mayewski, P.A., Rohling, E.E., Stager, J.C., Karlen, W., Maasch, K.A., Meeker, L.D., Meyerson, E.A., Gasse, F., van Kreveld, S., Holmgren, K., Lee-Thorp, J., Rosqvist, G. Rack, F., Staubwasser, M., Schneider, R.R. and Steig, E.J.  2004.  Holocene climate variability.  Quaternary Research 62: 243-255.

What was done
The sixteen authors of this paper, who hail from six different countries, examine some fifty globally distributed paleoclimate records in search of evidence for what they call rapid climate change (RCC) over the Holocene.  This terminology is not to be confused with the rapid climate changes typical of glacial periods, but is used in the place of what the authors call the "more geographically or temporally restrictive terminology such as 'Little Ice Age' and 'Medieval Warm Period'."  Hence, RCC events, as they also call them, are multi-century periods of time characterized by extremes of thermal and/or hydrological properties, rather than the much shorter periods of time during which the changes that led to these situations took place.

What was learned
Mayewski et al. identify six RCCs during the Holocene: 9000-8000, 6000-5000, 4200-3800, 3500-2500, 1200-1000 and 600-150 cal yr BP, the last two of which intervals are, in fact, the "globally distributed" Medieval Warm Period and Little Ice Age, respectively.  In speaking further of these two periods, they say that "the short-lived 1200-1000 cal yr BP RCC event coincided with the drought-related collapse of Maya civilization and was accompanied by a loss of several million lives (Hodell et al., 2001; Gill, 2000), while the collapse of Greenland's Norse colonies at ~600 cal yr BP (Buckland et al., 1995) coincides with a period of polar cooling."

With respect to the causes of these and other Holocene RCCs, the international team of scientists says that "of all the potential climate forcing mechanisms, solar variability superimposed on long-term changes in insolation (Bond et al., 2001; Denton and Karlen, 1973; Mayewski et al., 1997; O'Brien et al., 1995) seems to be the most likely important forcing mechanism."  In addition, they note that "negligible forcing roles are played by CH4 and CO2," and that "changes in the concentrations of CO2 and CH4 appear to have been more the result than the cause of the RCCs."

What it means
It is becoming ever more clear that the millennial-scale oscillation of climate that has reverberated throughout the Holocene is indeed the result of similar-scale oscillations in some aspect of solar activity.  Consequently, Mayewske et al. suggest that "significantly more research into the potential role of solar variability is warranted, involving new assessments of potential transmission mechanisms to induce climate change and potential enhancement of natural feedbacks that may amplify the relatively weak forcing related to fluctuations in solar output."  We couldn't agree more, for until these mechanisms have been elucidated to everyone's satisfaction, the world's climate alarmists will continue to ignore the mountains of evidence that link millennial-scale climate change with similar-scale solar variability, pushing the adoption of wrong-headed energy policies to the serious detriment of man and nature alike.

Bond, G., Kromer, B., Beer, J., Muscheler, R., Evans, M.N., Showers, W., Hoffmann, S., Lotti-Bond, R., Hajdas, I. and Bonani, G.  2001.  Persistent solar influence on North Atlantic climate during the Holocene.  Science 294: 2130-2136.

Buckland, P.C., Amorosi, T., Barlow, L.K., Dugmore, A.J., Mayewski, P.A., McGovern, T.H., Ogilvie, A.E.J., Sadler, J.P. and Skidmore, P.  1995.  Bioarchaeological evidence and climatological evidence for the fate of Norse farmers in medieval Greenland.  Antiquity 70: 88-96.

Denton, G.H. and Karlen, W.  1973.  Holocene climatic variations: their pattern and possible cause.  Quaternary Research 3: 155-205.

Gill, R.B.  2000.  The Great Maya Droughts: Water, Life, and Death. University of New Mexico Press, Albuquerque, New Mexico, USA.

Mayewski, P.A., Meeker, L.D., Twickler, M.S., Whitlow, S., Yang, Q., Lyons, W.B. and Prentice, M.  1997.  Major features and forcing of high-latitude northern hemisphere atmospheric circulation using a 110,000-year-long glaciochemical series.  Journal of Geophysical Research 102: 26,345-26,366.

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.