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The Medieval Warm Period in Southeast Uruguay ... and Beyond
Bracco, R., del Puerto, L., Inda, H., Panario, D., Castineira, C. and Garcia-Rodriguez, F. 2011. The relationship between emergence of mound builders in SE Uruguay and climate change inferred from opal phytolith records. Quaternary International 245: 62-73.

As a backdrop for studying the emergence and development of prehistoric mound building in southeast Uruguay, the authors of this intriguing paper employed paleoclimatic data to obtain a picture of how the climate of the region changed over the course of the past 7000 years.

What was done
Focusing on the coastal lagoons within the Merin Lagoon basin, which is located between 31-34°S and 52-54°W in the easternmost part of the South American plains, Bracco et al. state that paleolimnological investigations were initiated there in AD 2000 by a multidisciplinary group of researchers that studied past climate conditions via "multiproxy analyses (i.e., diatoms, opal phytoliths, pollen, molluscs, sediments, geochemistry, thin sections), together with radiocarbon dating." And working predominantly with phytoliths found within various sediment cores, they derived 7000-year histories of both a temperature and a humidity index.

What was learned
Of most interest to us, is the fact that straddling the division of the last two millennia, the South American scientists found a period (AD 750-1350) that "was characterized by warmer and wetter conditions than those of the present," which matches well with the timeframe of the Medieval Warm Period, as can be seen on the Interactive Map and Time Domain Plot of our Medieval Warm Period Project. And within this period they say "there are two peaks of extreme humid and warm events," the second of which "fits chronologically into the 'Warm Period' (Broecker, 2001; Roberts, 2009), whose occurrence has been already pointed out by Iriondo and Garcia (1993) and Prevosti et al. (2004) in this region."

What it means
These findings help to establish the global nature of the Medieval Warm Period that climate alarmists are so loath to acknowledge. And to provide even more support for this view of the world, Bracco et al. write that the results they present "are consistent with other paleoclimatic reconstructions (Bracco et al., 2005; Garcia-Rodriguez et al., 2009) and the synthesis presented by Mancini et al. (2005), and they are partially consistent with other regional studies (Iriondo and Garcia, 1993; Prieto, 1996, 2000; Iriondo, 1999; Panario and Gutierrez, 1999; Tonni et al., 1999; Zarate et al., 2000; Prieto et al., 2004; Quattrocchio et al., 2008; Piovano et al., 2009, in Argentina; Behling, 1995, 2002, 2007; Melo et al., 2003; Moro et al., 2004, in Brazil." And this ever-expanding body of empirical findings continues to add ever more weight to the reality of the millennial-scale cycling of our planet's climate, which after the passing of the Little Ice Age that followed the Medieval Warm Period is likely what has most recently ushered us into the Current Warm Period.

Behling, H. 1995. Late Quaternary environmental history from 5 new sites in the Brazilian tropics. Abstracts, 14th INQUA Congress, Berlin, Germany, p. 25.

Behling, H. 2002. South and Southeast Brazilian grasslands during Late Quaternary times: a synthesis. Paleogeography, Palaeoclimatology, Palaeoecology 177: 19-27.

Behling, H. 2007. Late Quaternary vegetation, fire and climate dynamics of Serra do Aracatuba in the Atlantic coastal mountains of Parana State, southern Brazil. Vegetation, History and Archaeobotany 16: 77-85.

Bracco, R., del Puerto, L., Inda, H. and Castineira, C. 2005. Middle-late Holocene cultural and environmental dynamics in the east of Uruguay. Quaternary International 132: 37-45.

Broecker, W. 2001. Was the Medieval Warm Period global? Science 291: 1497-1499.

Garcia-Rodriguez, F., Piovano, E., del Puerto, L., Inda, H., Stutz, S., Bracco, R., Panario, D., Cordoba, F., Sylvestre, F. and Ariztegui, D. 2009. South American lake paleo-records across the Pampean Region. PAGES News 17: 115-117.

Iriondo, M. 1999. Climate changes in the South American plains: record of a continent-scale oscillation. Quaternary International 57/58: 93-112.

Iriondo, M. and Garcia, N. 1993. Climate variation in the Argentine plains during the last 18,000 years. Palaeogeography, Palaeoclimatology, Palaeoecology 101: 209-220.

Mancini, M., Paez, M.M., Prieto, A.R., Stutz, S., Tonello, M. and Vilanova, I. 2005. Mid-Holocene climate variability reconstruction from pollen records (32°-52°S, Argentina). Quaternary International 132: 47-59.

Melo, M.S., Giannini, P.C.F., Pessenda, L.C. and Brandt Neto, M. 2003. Holocene paleoclimatic reconstruction based on the Lagoa Dourada deposits, southern Brazil. Geologica Acta 1: 289-302.

Moro, R., Bicudo, C., de Melo, M. and Schmitt, J. 2004. Paleoclimate of the late Pleistocene and Holocene at Lagoa Dourada, Parana State, southern Brazil. Quaternary International 114: 87-99.

Panario, D. and Gutierrez, O. 1999. The continental Uruguayan Cenozoic: and overview. Quaternary International 62: 75-84.

Piovano, E.L., Ariztegui, D., Cordoba, F., Coccale, M. and Sylvestre, F. 2009. Hydrological variability in South America below the Tropico of Capricorno (Pampas and Patagonia, Argentina) during the last 13.0 ka. In: Vimeux, F., Sylvestre, F. and Khodri, M. (Eds.). Past Climate Variability from the Last Glacial Maximum to the Holocene in South America and Surrounding Regions. Developments in Paleoenvironmental Research Series (DPER), Springer, New York, New York, USA, pp. 323-351.

Prevosti, F.J., Bonomo, M. and Tonni, E.P. 2004. La distribucion de Chrysocyon brachyurus (Illiger, 1811) (mammalia: carnivore: canidae) durante el Holoceno en la Argentina; Implicancias paleoambientales. Mastozoologia neotropical 11: 27-43.

Prieto, A.R., 1996. Late Quaternary vegetational and climate change in the Pampa Grassland of Argentina. Quaternary Research 54: 73-88.

Prieto, A.R. 2000. Vegetational history of the Late Glacial-Holocene transition in the grasslands of Eastern Argentina. Palaeogeography, Palaeoclimatology, Palaeoecology 157: 167-188.

Prieto, A.R., Blasi, A., De Francesco, C. and Fernandez, C. 2004. Environmental history since 11,000 14C yr B.P. of the northeastern Pampas, Argentina, from alluvial sequences of the Lujan River. Quaternary Research 62: 146-161.

Quattrocchio, M.E., Borromei, A.M., Deschamps, C.M., Grill, S.C. and Zavala, C.A. 2008. Landscape evolution and climate changes in the Late Pleistocene-Holocene, southern Pampa (Argentina): evidence from palynology, mammals and sedimentology. Quaternary International 181: 123-138.

Roberts, N. 2009. Holocene climates. In: Gornitz, V. (Ed.). Encyclopedia of Paleoclimatology and Ancient Environments. Springer, New York, New York, USA, pp. 438-441.

Tonni, E.P., Cione, A.L. and Figini, A.J. 1999. Predominance of arid climates indicated by mammals in the pampas of Argentina during the Late Pleistocene and Holocene. Palaeogeography, Palaeoclimatology, Palaeoecology 147: 257-281.

Zarate, M., Kemp, R.A., Espinosa, M. and Ferrero, L. 2000. Pedosedimentary and palaeoenvironmental significance of a Holocene alluvial sequence in the southern Pampas, Argentina. The Holocene 10: 481-488.

Reviewed 2 May 2012