The professor -- who holds positions in both the Institute of Arctic and Alpine Research and the Department of Civil, Environmental and Architectural Engineering of the University of Colorado at Boulder (USA) -- begins by acknowledging that for all the success of air- and space-borne observations of glaciers and ice sheets, "certain long-standing objectives have consistently eluded researchers," such as obtaining trustworthy observations of basal sliding and calving, as well as an improved understanding of subglacial processes, while further writing that "at present, the foundations of our theoretical knowledge of subglacial sliding and iceberg calving are not very different than what was available at the time of the First IPCC Assessment (Houghton et al., 1990)."

"As was the case nearly three decades ago," as Pfeffer continues, "basal sliding and calving remain obscure but exert critical controls on glacier and ice sheet dynamics," and he notes that as a result, "the lack of detailed observations of basal topography, temperature, and other boundary conditions in critical regions further complicates modeling efforts." In fact, he writes that the situation is so bleak that researchers "have still not closed the gaps in our knowledge to a degree that 'sliding laws' can be reliably and broadly implemented in numerical models," even adding that "no clear solution to this problem is in sight."

Pfeffer additionally reports that there has been "no comprehensive, global upscaled compilation of glacier and ice cap loss rates after 2005," stating that "without any proper accounting of the aggregate glacier and ice cap loss rate, the net loss from land ice cannot be reliably calculated." And without such observations, he adds that "no reliable assessment of contemporary rates of sea level rise can be made," commenting that "without this knowledge, projections of sea level rise are blind to future contributions from glaciers and ice caps."

In concluding his "weakness" commentary, Pfeffer states that our ability to project what glacier and ice discharge will actually be in years and decades to come "is grossly compromised, both by lack of basic inventory knowledge (where are the glaciers and how big are they?) and up-to-date observations of their rate of change." Thus, there is still much important work to be done in the area of land-ice/sea-level interactions before we can have much confidence in what the world's climate alarmists are currently predicting about future sea level rise.

Sherwood, Keith and Craig Idso

References
Houghton, J.T., Jenkins, G.J. and Ephraums, J.J. (Eds.). 1990. Climate Change: The IPCC Scientific Assessment. Cambridge University Press, Cambridge, UK.

Pfeffer, W.T. 2011. Land ice and sea level rise: A thirty-year perspective. Oceanography 24: 94-111.