Reference
Jenny, B., Valero-Garces, B.L., Urrutia, R., Kelts, K., Veit, H., Appleby, P.G. and Geyh M. 2002. Moisture changes and fluctuations of the Westerlies in Mediterranean Central Chile during the last 2000 years: The Laguna Aculeo record (33°50'S). Quaternary International 87: 3-18.
What was done
The authors studied geochemical, sedimentological and diatom-assemblage data derived from sediment cores extracted from one of the largest natural lakes in Central Chile (Laguna Aculeo), in order to obtain information about the hydrologic climate of that region over the past two millennia.
What was learned
From 200 BC, when the record began, until AD 200, conditions were primarily dry. This period of time coincides with the latter part of what is often referred to as the Roman Warm Period (see our Journal Review of McDermott et al., 2001). Subsequently, from AD 200-700 - with a slight respite in the central hundred years of that period - there was a high frequency of flood events. This period of time likewise coincides with what is generally called the Dark Ages Cold Period (see again McDermott et al., 2001). Then came a several-hundred-year period of less flooding that was coeval with what is generally referred to as the Medieval Warm Period. This more benign period was then followed by another period of frequent flooding from 1300-1700 - which picked up again about 1850 - that was of the same timeframe as the Little Ice Age.
What it means
The striking temporal correspondence of these Central Chile millennial-scale climatic oscillations and those depicted in proxy climate records from Europe bear testimony to the global nature of this important aspect of the planet's natural climate variability over two full cycles of oscillatory behavior. How can anyone doubt the reality and worldwide nature of these climatic oscillations? Or the fact that the warming of the past century (and some possible yet-future warming) is nothing more than the next phase of this ongoing, and anthropogenically-unaided, cyclical behavior, i.e., earth's natural and inevitable ascendancy into what we call the Modern Warm Period?
Reference
McDermott, F., Mattey, D.P. and Hawkesworth, C. 2001. Centennial-scale Holocene climate variability revealed by a high-resolution speleothem ð18O record from SW Ireland. Science 294: 1328-1331.
Reviewed 20 February 2002