Background
The authors state that "despite many studies that have pointed to ... the validity of the classical climatic oscillations described for the Late Holocene (Medieval Warm Period, Little Ice Age, etc.), there is a research line that suggests the non-global signature of these periods (IPCC, 2001; Jones and Mann, 2004)." Noting that "the best way to solve this controversy would be to increase the number of high-resolution records covering the last millennia and to increase the spatial coverage of these records," they proceed to do just that.

What was done
Working with a number of sediment cores retrieved from a river-fed wetland that is flooded for approximately seven months of each year in Las Tablas de Daimiel National Park (39.4°N, 3.8°W, south central Iberian Peninsula, Spain), Garcia et al. employed "a high resolution pollen record in combination with geochemical data from sediments composed mainly of layers of charophytes alternating with layers of vegetal remains plus some detrital beds" to reconstruct "the environmental evolution of the last 3000 years."

What was learned
The six Spanish researchers were able to identify five distinct climatic stages: "a cold and arid phase during the Subatlantic (Late Iron Cold Period, < B.C. 150), a warmer and wetter phase (Roman Warm Period, B.C. 150-A.D. 270), a new colder and drier period coinciding with the Dark Ages (A.D. 270-900), the warmer and wetter Medieval Warm Period (A.D. 900-1400), and finally a cooling phase (Little Ice Age, >A.D. 1400)."

What it means
Noting that "the Iberian Peninsula is unique, as it is located at the intersection between the Mediterranean and the Atlantic, Europe and Africa, and is consequently affected by all of them," Garcia et al. significantly advance the likelihood that "the classical climatic oscillations described for the Late Holocene (Medieval Warm Period, Little Ice Age, etc.)" were indeed both real and global in scope, as becomes ever more evident each and every week with our posting of the results of a new Medieval Warm Period study on our website. In addition, Garcia et al. state that the Medieval Warm Period "is identified at about a similar date all around the world (China: Chu et al., 2002; Arabia, Fleitmann et al., 2004; Africa: Filippi and Talbot, 2005; Iceland: Doner, 2003; central Europe: Filippi et al., 1999; New Guinea: Haberle and David, 2004; USA: Cabaniss Pederson et al., 2005: Argentina: Mauquoy et al., 2004; etc.," and that "comparable changes are described by Desprat et al. (2003), Julia et al. (1998) and Riera et al. (2004) in northwest, central and northeast Spain." Truly, the evidence for the global scope of the Medieval Warm Period is overwhelming.

References
Cabaniss Pederson, D., Peteet, D.M., Kurdyla, D. and Guilderson, T. 2005. Medieval warming, Little Ice Age, and European impact on the environment during the last millennium in the lower Hudson Valley, New York, USA. Quaternary Research 63: 238-249.

Chu, G., Li, J., Sun, O., Lu, H., Gu, Z., Wang, W. and Liu, T. 2002. The "Mediaeval Warm Period" drought recorded in Lake Huguangyan, tropical South China. The Holocene 12: 511-516.

Desprat, S., Sanchez-Goni, M.F. and Loutre, MF. 2003. Revealing climatic variability of the last three millennia in northwestern Iberia using pollen influx data. Earth and Planetary Science Letters 213: 63-78.

Doner, L. 2003. Late-Holocene paleoenvironments of northwest Iceland from lake sediments. Palaeogeography, Palaeoclimatology, Palaeoecology 193: 535-560.

Filippi, M.L., Lambert, P., Hunziker, J., Kubler, B. and Bernasconi, S. 1999. Climatic and anthropogenic influence on the stable isotope record from bulk carbonates and ostracodes in Lake Neuchatel, Switzerland, during the last two millennia. Journal of Paleolimnology 21: 19-34.

Filippi, M.L. and Talbot, M.R. 2005. The palaeolimnology of northern Lake Malawi over the last 25 ka based upon the elemental and stable isotopic composition of sedimentary organic matter. Quaternary Science Reviews 24: 1303-1328.

Fleitmann, D., Burns, S.J., Neff, U., Mudelsee, M., Mangini, A. and Matter, A. 2004. Palaeoclimatic interpretation of high-resolution oxygen isotope profiles derived from annually laminated speleothems from Southern Oman. Quaternary Science Reviews 23: 935-945.

Haberle, S.G. and David, B. 2004. Climates of change: human dimensions of Holocene environmental change in low latitudes of the PEPII transect. Quaternary International 118: 165-179.

IPCC. 2001. Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change.

Jones, P.D. and Mann, M.E. 2004. Climate over past millennia. Reviews of Geophysics 42: 10.1029/2003RG000143.

Julia, R., Burjachs, F., Dasi, M.J., Mezquita, F., Miracle, M.R., Roca, J.R. Seret, G. and Vicente, E. 1998. Meromixis origin and recent trophic evolution in the Spanish mountain lake La Cruz. Aquatic Sciences 60: 279-299.

Mauquoy, D., Blaauw, M., van Geel, B., Borromei, A., Quattrocchio, M., Chambers, F. and Possnert, G. 2004. Late Holocene climatic changes in Tierra del Fuego based on multiproxy analyses of peat deposits. Quaternary Research 61: 148-158.

Riera, S., Wansard, G. and Julia, R. 2004. 2000-year environmental history of a karstic lake in the Mediterranean Pre-Pyrenees: the Estanya lakes (Spain). Catena 55: 293-324.