The medieval warm period is vastly inconvenient to Warmists and they try on occasions to erase it from their data summaries. But it is not going away so their next line of defence is to say it was a Northern hemisphere event only. That was always pretty absurd (and raised more questions than it answered) but the study reported below gives it another kick in the pants by showing that the Northern and Southern hemisphere climates move in tandem. See also here and here.
Two of the most important questions in paleoclimatology are, how are the climates of the Northern and Southern Hemispheres linked, and what are the roles of the high latitudes and the tropics in driving and transmitting climate changes? Past investigations have concentrated on the study of large, rapid climate changes like deglaciations or the Younger Dryas because they are the easiest ones to see and to date. Licciardi et al. (p. 1677) expand the scope of these investigations by determining precise cosmogenic isotope ages for glacial moraines formed in the Peruvian Andes during the Holocene (the last 11,000 years). The precision of these data reveals a broad correlation between Peruvian glacial advances and climate in the North Atlantic region, revealing important climate linkages between the tropics and higher latitudes.
Journal abstract follows:
Holocene Glacier Fluctuations in the Peruvian Andes Indicate Northern Climate Linkages
By Joseph M. Licciardi et al.
The role of the tropics in triggering, transmitting, and amplifying interhemispheric climate signals remains a key debate in paleoclimatology. Tropical glacier fluctuations provide important insight on regional paleoclimatic trends and forcings, but robust chronologies are scarce. Here, we report precise moraine ages from the Cordillera Vilcabamba (13°20'S) of southern Peru that indicate prominent glacial events and associated climatic shifts in the outer tropics during the early Holocene and late in the "Little Ice Age" period. Our glacier chronologies differ from the New Zealand record but are broadly correlative with well-dated glacial records in Europe, suggesting climate linkages between the tropics and the North Atlantic region.
Science 25 September 2009: Vol. 325. no. 5948, pp. 1677 - 1679
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