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Globally Synchronous Cooling 2800 Years Ago
Chambers, F.M., Mauquoy, D., Brain, S.A., Blaauw, M. and Daniell, J.R.G. 2007. Globally synchronous climate change 2800 years ago: Proxy data from peat in South America. Earth and Planetary Science Letters 253: 439-444.

What was done
The authors present new proxy climate data they obtained from a bog in the Valle de Andorra northeast of Ushuaia, Tierra del Fuego, Argentina, which data, they emphasize, are "directly comparable" with similar proxy climate data obtained in numerous studies conducted in European bogs, "as they were produced using identical laboratory methods [our italics]." This latter point is very important because ...

What was learned
.. Chambers et al. say their new South American data show there was "a major climate perturbation at the same time as in northwest Europe," which they describe as "an abrupt climate cooling" that occurred approximately 2800 years ago, and that "its timing, nature and apparent global synchronicity lend support to the notion of solar forcing of past climate change, amplified by oceanic circulation."

What it means
The five European researchers say their finding "that rapid, high-magnitude climate changes might be produced within the Holocene by an inferred decline in solar activity (van Geel et al., 1998, 2000, 2003; Bond et al., 2001; Blaauw et al., 2004; Renssen et al., 2006) has implications for rapid, high-magnitude climate changes of the opposite direction - climatic warmings, possibly related to increases in solar activity." In this regard, they further note that "for the past 100 years any solar influence would for the most part have been in the opposite direction (i.e., to help generate a global climate warming) to that inferred for c. 2800-2710 cal. BP." And they conclude that this observation "has implications for interpreting the relative contribution of climate drivers of recent 'global warming'," implying that a solar-induced, rather than a CO2-induced, climate driver may have been the primary cause of 20th-century global warming.

Blaauw, M., van Geel, B. and van der Plicht, J. 2004. Solar forcing of climate change during the mid-Holocene: indications from raised bogs in The Netherlands. The Holocene 14: 35-44.

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.

Renssen, H., Goosse, H. and Muscheler, R. 2006. Coupled climate model simulation of Holocene cooling events: solar forcing triggers oceanic feedback. Climate Past Discuss. 2: 209-232.

Van Geel, B., Heusser, C.J., Renssen, H. and Schuurmans, C.J.E. 2000. Climatic change in Chile at around 2700 BP and global evidence for solar forcing: a hypothesis. The Holocene 10: 659-664.

Van Geel, B., van der Plicht, J., Kilian, M.R., Klaver, E.R., Kouwenberg, J.H.M., Renssen, H., Reynaud-Farrera, I. and Waterbolk, H.T. 1998. The sharp rise of ?14C ca. 800 cal BC: possible causes, related climatic teleconnections and the impact on human environments. Radiocarbon 40: 535-550.

Van Geel, B., van der Plicht, J. and Renssen, H. 2003. Major ?14C excursions during the Late Glacial and early Holocene: changes in ocean ventilation or solar forcing of climate change? Quaternary International 105: 71-76.

Reviewed 4 July 2007