The Medieval Warm Period and Little Ice Age in Northern Patagonia

Sepulveda et al. (2009) write that "deciphering climate variability in the Southern Hemisphere and particularly from southern South America - the only continental land mass lying between 38°S and the Antarctic Circle - is crucial for documenting the inter-hemispheric synchronicity of recent abrupt climate changes and thereby determining their ultimate cause(s)," as well as for "predicting future abrupt climate changes."The eight researchers, therefore, conducted "a high-resolution multi-proxy study including the elemental and isotopic composition of bulk organic matter, land plant-derived biomarkers, and alkenone-based sea-surface temperature (SST) [derived] from a marine sedimentary record obtained from the Jacaf Fjord in northern Chilean Patagonia [44°20.00'S, 72°58.15'W]," in order to provide "a detailed reconstruction of continental runoff, precipitation and summer SST spanning the last 1750 years." So what did they find?

The Chilean, German and US scientists report that they "observed two different regimes of climate variability in [their] record: a relatively dry/warm period before 900 cal yr BP (higher runoff and average SST 1°C warmer than present day) and a wet/cold period after 750 cal yr BP (higher runoff and average SST 1°C colder than present day)," which they associated with the Medieval Warm Period and Little Ice Age, respectively.

In the words of the research team, "the reasonably good correlation between our results (particularly SST) and other continental and marine archives from central-south Chile, Peru, and Antarctica ... confirms the occurrence of globally important climatic anomalies such as the Medieval Warm Period and the Little Ice Age." And, of course, their SST data indicate that the current level of warmth in that part of the world still has a long way to go before equaling the warmth experienced there a thousand and more years ago, which suggests that the region's current level of warmth is neither unprecedented nor unnatural - and therefore need not be CO₂-induced.