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The Little Ice Age in the Tropical Andes of Bolivia
Rabatel, A., Francou, B., Jomelli, V., Naveau, P. and Grancher, D. 2008. A chronology of the Little Ice Age in the tropical Andes of Bolivia (16°S) and its implications for climate reconstruction. Quaternary Research 70: 198-212.

In an attempt to rewrite climatic history, certain scientists have claimed that the Little Ice Age (LIA) and the prior Medieval Warm Period (MWP) were neither global phenomena nor strong enough where they did occur to have a discernable influence on mean global air temperature, in order to portray the warming of the last decades of the 20th century as highly unusual, which they equate with anthropogenic-induced, which they associate --incorrectly, we believe -- with the historical rise in the atmosphere's CO2 concentration. Hence, we continually scan the scientific literature, looking for data that demonstrate that the LIA and MWP were both real and global in nature.

What was done
In the case we consider here, Rabatel et al. used lichenometry to reconstruct glacier movements in the Bolivian Andes over the last several centuries, seeking to answer two important questions they posed for themselves: (1) "Were glacier fluctuations during the LIA in the tropics of the same magnitude as those in mid-latitudes?" and (2) "Were these fluctuations synchronous with others observed elsewhere, suggesting that climate changes during this period were similar and produced the same effects worldwide?"

What was learned
The five researchers report that "the maximum and the main phases of the LIA glacier evolution in Bolivia are in agreement with those of the well-documented glaciers in mid-latitude mountain ranges." More specifically, they write that "the glacier maximum in Bolivia is quite similar to glacier expansions observed in the European Alps in the mid/late 17th century (Le Roy Ladurie, 2004) and during the first half of the 18th century in Scandinavian mountain ranges (Nesje and Dahl, 2000), the Canadian Rockies (Luckman, 2000), the Patagonian Andes (Luckman and Villalba, 2001) and the Southern Alps of New Zealand (Winckler, 2004)." In addition, they say that "the trend to Bolivian glacier recession accelerated after AD 1870 up to the beginning of the 20th century," and that "this acceleration in the recession coincides with the decrease in surface area of many glaciers worldwide, particularly in the Alps (Grove, 1988)."

As for the magnitude and source of the cooling in the Bolivian Andes during the LIA, Rabatal et al. estimate it to have been 1.1 to 1.2°C below that of present conditions, noting that at this time there was a "striking coincidence between the glacier expansion in this region of the tropics and the decrease in solar irradiance: the so-called 'Maunder minimum' (AD 1645-1715) during which irradiance might have decreased by around 0.24% (Lean and Rind, 1998) and could have resulted in an atmospheric cooling of 1°C worldwide (Rind et al., 2004)."

What it means
Clearly, the evidence for a largely synchronous and global Little Ice Age is essentially irrefutable, much to the chagrin of the world's climate alarmists.

Grove, J.M. 1988. The Little Ice Age. Methuen, London, UK.

Lean, J. and Rind, D. 1998. Climate forcing by changing solar radiation. Journal of Climate 11: 3069-3094.

Le Roy Ladurie, E. 2004. Histoire humaine et compare du climat. Canicules et glaciers 13e-18e siècle. Fayard, Paris, France.

Luckman, B.H. 2000. The Little Ice Age in the Canadian Rockies. Geomorphology 32: 357-384.

Luckman, B.H. and Villalba, R. 2001. Assessing the synchronicity of glacier fluctuations in the western Cordillera of the Americas during the last millennium. In: Markgraf, V. (Ed.), Inter-Hemispheric Climate Linkages. Academic Press, San Diego, USA, pp. 119-140.

Nesje, A. and Dahl, S.O. 2000. Glaciers and Environmental Change. Arnold, London, UK.

Rind, D., Shindell, D., Perlwitz, J., Lerner, J., Lonergan, P., Lean, J. and McLinden, C. 2004. The relative importance of solar and anthropogenic forcing of climate change between the Maunder minimum and the present. Journal of Climate 17: 906-929.

Winkler, S. 2004. Lichenometric dating of the Little Ice Age maximum in Mt. Cook National Park, Southern Alps, New Zealand. The Holocene 14: 911-920.

Reviewed 17 December 2008