What was done
The authors applied a three-dimensional ice-sheet model to the Langjokull Ice Cap that includes a component describing glacier hydrology and thereby provides a direct link to the empirical record derived from glaciofluvial sediments deposited in proglacial lake Hvitarvatn, where intensive coring -- which yielded data on grain size, lithofacies, tephras, diatoms, total organic carbon, biogenic silica, magnetic susceptibility, wet bulk density and dropstones or ice-rafted debris -- and multi-beam high-resolution bathymetry and reflection seismic surveys were carried out from 2001 to 2005. The results of this exercise, when driven by Greenland ice-core oxygen isotope records and constrained by the implications of the sediment core data, were then used to construct a history of the climatic conditions of central Iceland throughout the Holocene.

What was learned
Flowers et al. say their comprehensive analyses suggest that (1) temperatures of the Holocene Thermal Maximum in central Iceland were likely 3-4°C warmer than those of the 1961-1990 period, that (2) the maximum Holocene stand of the ice cap occurred during the Little Ice Age, that (3) there was little to no ice advance into Hvitarvatn before about 1000 years before present, and (4) the lake area occupied by ice was much greater during the Little Ice Age than at any previous time.

What it means
One implication of the six researchers' findings is that it should not have been surprising to have seen the earth experience a 20th-century warming that climate alarmists like to characterize as having been "unprecedented," since during this period the planet was emerging from the coldest period of the current interglacial. Another implication is that it should not be surprising to see the earth continue to warm in the future, as it has not yet reached the level of warmth it experienced for a few millennia during the central portion of the Holocene. In addition, an equivalent degree of future warming should not have inordinately bad consequences for earth's plant and animal life, since all species living on the planet today obviously survived the much warmer temperatures characteristic of the Holocene Thermal Maximum.