What was done
Based on various types of evidence collected by many investigators over the years, the author constructed a 20th-century history of glacial fluctuations in the Cordillera Blanca of Peru (77°30'W, 9°S), which is the largest glaciated area located within the earth's tropics.

What was learned
Georges reports that "the beginning of the century was characterized by a glacier recession of unknown extent, followed by a marked readvance in the 1920s that nearly reached the Little Ice Age maximum."  Then came the 1930s-1940s shrinkage of the glacial mass that was, in his words, "very strong," after which there was a period of quiescence that was followed by an "intermediate retreat from the mid-1970s until the end of the century."

In comparing the two periods of glacial wasting, Georges says that "the intensity of the 1930s-1940s retreat was more pronounced than that of the one at the end of the century."  In fact, his graph of the ice area lost in both time periods suggests that the rate of wastage in the 1930s-1940s was twice as great as that of last two decades of the century.

What it means
Climate alarmists are always alarmed at new reports of glacial retreat, and they like to equate the magnitude of current glacial wasting with the current global temperature level, which they claim is unprecedented over the past two millennia.  Pursuing that tack here, one would have to conclude that the level of warmth in this part of Peru during the 1930s and 40s must have been significantly greater than that of the 1980s and 90s.  Interestingly, for another part of the planet cold enough to produce and maintain glaciers, i.e., latitudes north of 70°N, that conclusion is correct (see our Editorial of 12 Jan 2005).  These newest glacial observations from Peru, therefore, do little - make that nothing - to advance the climate alarmists' cause.

It is also interesting to note that Georges is quite at ease talking about the Little Ice Age south of the equator in Peru, which is a very long way from the lands that border the North Atlantic, which is the only region on earth where the world's climate alarmists willingly admit the existence of this chilly era of the planet's climatic history.  It is even more interesting to note that the glacial extensions of the Cordillera Blanca in the late 1920s were almost equivalent to those experienced there in the depths of the Little Ice Age, which is generally recognized as being the coldest period of the entire Holocene, or current interglacial, which suggests it is not at all strange that there should be a sizable warming of that part of the planet subsequent to its achieving a level of cold that was unprecedented over the past several millennia.