Background
Kilimanjaro, the highest free-standing mountain in the world, was long renowned for its summit glaciers, immortalized by Ernest Hemingway in his famous short story "The Snows of Kilimanjaro." Over the first few years of the current century, its disappearing summit ice fields were once again made famous, this time by political luminaries such as Al Gore, Hillary Clinton and John McCain, who cited them as unmistakable evidence of the deleterious consequences of human-induced global warming. With the appearance of the research reports of Molg et al. (2003), Kaser et al. (2004), Molg and Hardy (2004), Cullen et al. (2006) and Mote and Kaser (2007), however, it has become clear to all but the most blind, that rising temperatures have had little to do with Kilimanjaro's disappearing ice, as the findings of Duane et al. (2008) also suggest.

What was done
Between September 2004 and January 2006, Duane et al. (2008) collected temperature and relative humidity readings 1.5 meters above ground level at 11,600 hourly intervals at seven locations over an elevation range of 3,910 meters on the southwestern side of Kilimanjaro, after which they determined the implications of their data for the shrinking ice fields atop the mountain.

What was learned
The researchers say their data show that temperatures remained well below freezing at their uppermost measurement site, so that "patterns of cloud cover and humidity are central to understanding glacier-climate interactions" at the ice fields. In this regard, they further state that "nearly all of the moisture in the atmosphere at the higher levels of the mountain is brought up from lower elevations through the mechanism of the montane thermal circulation," and that their data point strongly "to the lower slopes of Kilimanjaro as a moisture source for both the snows that feed the summit glaciers and the clouds that impact their surface energy balance." They also say their data suggest there is a "net export of moisture out of the forest zone (upslope) during the daylight hours," noting that "it could be that land-use changes in the forest zone as a result of deforestation have reduced the efficiency of this moisture supply to the higher reaches of the mountain."

What it means
Stating that their work shows "the importance of moisture transport upslope to the summit of Kilimanjaro," Duane et al. thus come down on the side of the many other researchers who have concluded, in their words, that "the reasons for the rapid decline in Kilimanjaro's glaciers are not primarily due to increased air temperatures, but a lack of precipitation."

References
Cullen, N.J., Molg, T., Kaser, G., Hussein, K., Steffen, K. and Hardy, D.R. 2006. Kilimanjaro glaciers: Recent areal extent from satellite data and new interpretation of observed 20th century retreat rates. Geophysical Research Letters 33: 10.1029/2006GL027084.

Kaser, G., Hardy, D.R., Molg, T., Bradley, R.S. and Hyera, T.M. 2004. Modern glacier retreat on Kilimanjaro as evidence of climate change: Observations and facts. International Journal of Climatology 24: 329-339.

Molg, T. and Hardy, D.R. 2004. Ablation and associated energy balance of a horizontal glacier surface on Kilimanjaro. Journal of Geophysical Research 109: 10.1029/2003JD004338.

Molg, T., Hardy, D.R. and Kaser, G. 2003. Solar-radiation-maintained glacier recession on Kilimanjaro drawn from combined ice-radiation geometry modeling. Journal of Geophysical Research 108: 10.1029/2003JD003546.

Mote, P.W. and Kaser, G. 2007. The shrinking glaciers of Kilimanjaro: Can global warming be blamed? American Scientist 95: 318-325.