What was done
The Gangotri Glacier - situated in the Uttarkashi district of Uttranchal, Western Himalaya - holds a special place amongst all the Himalayan glaciers, due to its economic, social and religious significance as the source of the Holy Ganga.  The authors explore the nature of climate change in this region of India over the past 2000 years via pollen analyses of a 1.25-meter sediment profile in an outwash plain located about 2.5-3 km from the glacier's snout.

What was learned
Between 2000 and 1700 years ago, the authors' data reveal the existence of a cooler climate "than the one prevailing at present."  Comparing this result with the study of McDermott et al. (2001) in Ireland, we see that this period of time is a part of the Dark Ages Cold Period.  Between 1700 and 850 years ago, the authors' analysis indicates an "amelioration of climate."  From McDermott et al., we see that this period of time represents the transition from the depth of the Dark Ages Cold Period to the midst of the Medieval Warm Period.  Subsequent to 850 years ago, the authors' data show that the climate "became much cooler," indicative of its transition to Little Ice Age conditions.  Between 300 and 200 years ago, in fact, the authors note that the long-term "retreat of the Gangotri Glacier ceased, possibly with some minor advancement."  During the last 200 years, however - when the study of Esper et al. (2002) indicates there has been a rather steady warming of the planet - the glacier's snout has retreated by about 2 km.

What it means
The results of this study clearly demonstrate the exquisite harmony of climate change in the region of the North Atlantic Ocean and the distant Himalayas, providing ever-increasing evidence for the reality of the oscillatory climatic phenomenon that has brought the world the Medieval Warm Period, Little Ice Age and Modern Warm Period, as well - in this case - as the even earlier Dark Ages Cold Period.  This observation provides strong support for our contention (see our Editorial of 27 March 2002) that the warming of the last two centuries is most likely totally of natural origin and unrelated to the concomitant anthropogenic-induced rise in the air's CO2 content.

References
Esper, J., Cook, E.R. and Schweingruber, F.H.  2002.  Low-frequency signals in long tree-ring chronologies for reconstructing past temperature variability.  Science 295: 2250-2253.

McDermott, F., Mattey, D.P. and Hawkesworth, C.  2001.  Centennial-scale Holocene climate variability revealed by a high-resolution speleothem ð¹⁸O record from SW Ierland.  Science 294: 1328-1331.