What was done
In the words of the authors, they "present a summary of the evidence for suggested periods of glacier advance during the final phase of the Alpine Lateglacial and the Holocene," interweaving "data obtained from ¹⁰Be surface exposure dating, radiocarbon dating of wood and peat washed out from the presently melting glacier tongues, dendrochronological investigations on wood from the glacerized basins, tree-line studies and archaeological evidence."

What was learned
Ivy-Ochs et al. report that "the earliest Holocene (between 11.6 and about 10.5 ka) was still strongly affected by the cold climatic conditions of the Younger Dryas and the Preboreal oscillation," but that "at or slightly before 10.5 ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate." After 3.3 ka, however, they say that "climate conditions became generally colder and warm periods were brief and less frequent." Last of all, they indicate that "glaciers in the Alps attained their Little Ice Age maximum extents in the 14th, 17th and 19th centuries, with most reaching their greatest Little Ice Age extent in the final 1850/1860 AD advance [italics added]."

What it means
Like their alpine glacier counterparts in Scandinavia described by Nesje (2009), glaciers of the European Alps also reached their maximum Holocene extensions close to the end of the Little Ice Age, which means that at that point in time there existed the greatest potential for significant warming of the entire interglacial period; for in an oscillatory climatic regime, the point of lowest temperature decline also represents the point of the greatest potential for a significant temperature increase. Hence, it should only have been expected that the subsequent temperature recovery of the earth would likely be quite substantial, as there was a lot of prior cooling that had to be overcome in order to return the planet to a climatic state more characteristic of the bulk of the Holocene. And, since decreases in the atmosphere's CO2 concentration had absolutely nothing to do with the pre-1900 cooling of the planet (since there were no significant CO2 decreases over the Holocene), there is no reason to believe that 20th-century increases in the air's CO2 content had anything at all to do with the post-1900 warming of the planet, which was in no way unusual, unnatural or, frankly, unexpected.

Reference
Nesje, A. 2009. Latest Pleistocene and Holocene alpine glacier fluctuations in Scandinavia. Quaternary Science Reviews 28: 2119-2136.