Geologist Dr. Don Easterbrook does take down of new study claiming ‘Unprecedented Recent Summer Warmth in Arctic Canada’ — ‘Bad assumptions, poor logic, and contrary to other evidence of Arctic temperatures’
Special to Climate Depot
Miller et al.’s “Unprecedented Recent Summer Warmth in Arctic Canada”: Bad assumptions, poor logic, and contrary to other evidence of Arctic temperatures.
Dr. Don J. Easterbrook, Western Washington University, Bellingham, WA –
Miller et al. radiocarbon dated 145 rooted tundra plants revealed by receding ice in the eastern Canadian Arctic and that it constitutes the first direct evidence that recent temperatures now exceed those of any century in the Holocene, including the Holocene Thermal Maximum. They further contend that (1) average summer temperatures of the last ~100 years were higher than any century in the past 44,000 years and suggest that present temperatures have not been exceeded in the past ~120,000 years, at or near the end of the last interglaciation, and (2) they conclude that this ‘unprecedented’ warming was caused by anthropogenic increases in greenhouse gases. So let’s look at some of the assumptions that form the basis for their conclusions and compare their conclusions to other Arctic data.
Figure 1 A. Baffin Island showing sample sites. Circles (color-coded by their 14C age) show the 135, <5 ka, sites where rooted plants were collected at receding ice cap margins; diamonds show sites dated >47 ka. Solid lines mark the margins of the LIS at the last glacial maximum and 9 ka [A. S. Dyke, 2004]. B. Detailed map of sites older than ~45 ka.
Assertions and assumptions by Miller et al.
[1] Mille el al. contend that “although glaciers are frequently associated with deep and widespread erosion, small, cold-based ice caps that mantle relatively flat terrain typically advance by lateral accretion rather than by basal flow, and are thus capable of preserving even the most delicate features of the landscape. As these ice caps recede, they often reveal rooted tundra plants that were living at the time snow and ice last covered the site.” They further contend that “Surface-elevation contours of the continental Laurentide Ice Sheet (LIS) show that all four ice caps with pre-Holocene dated plants were above the surface of the LIS at its last glacial maximum. These sites thus supported only local ice caps then as now. And, because the ice caps occupy flat summits of less than 0.2 km2 surrounded by steep slopes, ice thicknesses of more than 70 meters could not have been sustained.”
The assumptions in these statements are:…
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