What was done
The authors used mass balance measurements made on the two largest glaciers of the Polar Urals (the IGAN and Obruchev glaciers, ~67.5°N, 67.5°E) between 1957 and 1981 to develop a model of glacier mass balance based upon temperature and precipitation data they obtained from two meteorological stations situated about 100 km from the glaciers, after which they developed models of temperature and precipitation based upon local tree-ring data; and since the tree-ring data spanned the period AD 778-1990, they were able to develop temperature and precipitation histories for that extended period of time, which finally enabled them to reconstruct glacier mass balance back to AD 778.

What was learned
Kononov et al.'s plotted results indicate that from approximately AD 800-1075 there was an almost continuous state of negative glacier mass balance in the Polar Urals that was unequaled anywhere else in the record, which epoch they describe as being "remarkable for its steady glacier mass loss associated with the Medieval Warm Period." So great was the mass loss over this period, in fact, they ended up concluding that "the magnitude of negative mass balance for Polar Ural glaciers during the Medieval Warm Period and during the period of modern global warming is similar."

What it means
In his 21 March 2007 testimony before the United States Senate's Environment & Public Works Committee, the Honorable Al Gore spoke about what he called "a planetary emergency - a crisis that threatens the survival of our civilization and the habitability of the earth," stating in support of this contention (among other things) that "mountain glaciers are receding around the world."

By itself, however, this observation proves nothing. What is needed to assess the true nature of Gore's "planetary emergency" is a knowledge of how the current recession of mountain glaciers compares with prior recessions; and in the case of Polar Ural glaciers, it would appear that the current state of glacier recession is not materially different from that which occurred a full thousand years ago, during the Medieval Warm Period, when there was more than 100 ppm less CO2 in the air than there is today.

Consequently, it would appear that Gore's CO2-induced "climate crisis" may be neither a crisis nor CO2-driven!