Background
On the floor of the U.S. Senate during debate on bill S. 139, Senator John McCain told of his affection for the writings of Ernest Hemingway, especially his famous short story "The Snows of Kilimanjaro."  Then, showing photos of the magnificent landmark taken in 1993 and 2000, he attributed the decline of ice atop the mount during the intervening years to CO2-induced global warming, calling this attribution not only a fact, but a fact "that cannot be refuted by any scientist."

In subsequent debate on the same bill, Senator Hillary Clinton echoed Senator McCain's sentiments.  Displaying a second set of photos taken from the same vantage point in 1970 and 1999 (the first depicting "a 20-foot-high glacier" and the second "only a trace of ice"), she said that in those pictures "we have evidence in the most dramatic way possible of the effects of 29 years of global warming."

What was done
In our Editorial of 11 Feb 2004, we presented evidence that totally refutes the claims of Senators McCain and Clinton, highlighting the study of Molg et al. (2003b), who do the world of science (and politics) an important service by convincingly disproving the oft-stated claim that CO2-induced warming is what caused the dramatic receding of the ice fields of Kilimanjaro over the past century or more.  Now, with the assistance of two additional authors, Kaser et al. repeat the feat.

What was learned
In reviewing a wealth of pertinent data, the authors conclude that "changes in air humidity and atmospheric moisture content (e.g. Soden and Schroeder, 2000) seem to play an underestimated key role in tropical high-mountain climate (Broecker, 1997)."  Noting that all glaciers in equatorial East Africa exhibited strong recession trends over the past century, they report that "the dominant reasons for this strong recession in modern times are reduced precipitation (Kruss, 1983; Hastenrath, 1984; Kruss and Hastenrath, 1987; Kaser and Noggler, 1996) and increased availability of shortwave radiation due to decreases in cloudiness (Kruss and Hastenrath, 1987; Molg et al., 2003a)," both of which phenomena they relate to a dramatic drying of the regional atmosphere that occurred around 1880 and the ensuing dry climate that subsequently prevailed throughout the 20th century.

What it means
Kaser et al. demonstrate that all relevant "observations and facts" clearly indicate that "climatological processes other than air temperature control the ice recession in a direct manner" on Kilimanjaro, and that "positive air temperatures have not contributed to the recession process on the summit," directly contradicting Irion (2002) and Thompson et al. (2002), who, in their words, see the recession of Kilimanjaro's glaciers as "a direct consequence solely of increased air temperature."

In setting this record straight, Kaser et al. also contradict the claims of Senators McCain and Clinton.  And they show the hollowness of the additional claim of Senator McCain that his view of the subject "cannot be refuted by any scientist."

References
Broecker, W.S.  1997.  Mountain glaciers: records of atmospheric water vapor content?  Global Biogeochemical Cycles 4: 589-597.

Hastenrath, S.  1984.  The Glaciers of Equatorial East Africa.  D. Reidel, Norwell, MA, USA.

Irion, R.  2001.  The melting snows of Kilimanjaro.  Science 291: 1690-1691.

Kaser, G. and Noggler, B.  1996.  Glacier fluctuations in the Rwenzori Range (East Africa) during the 20th century - a preliminary report.  Zeitschrift fur Gletscherkunde and Glazialgeologie 32: 109-117.

Kruss, P.D.  1983.  Climate change in East Africa: A numerical simulation from the 100 years of terminus record at Lewis Glacier, Mount Kenya.  Zeitschrift fur Gletscherkunde und Glazialgeologie 19: 43-60.

Kruss, P.D. and Hastenrath, S.  1987.  The role of radiation geometry in the climate response of Mount Kenya's glaciers, part 1: Horizontal reference surfaces.  International Journal of Climatology 7: 493-505.

Molg, T., Georges, C. and Kaser, G.  2003a.  The contribution of increased incoming shortwave radiation to the retreat of the Rwenzori Glaciers, East Africa, during the 20th century.  International Journal of Climatology 23: 291-303.

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

Soden, B.J. and Schroeder, S.R.  2000.  Decadal variations in tropical water vapor: a comparison of observations and a model simulation.  Journal of Climate 13: 3337-3341.

Thompson, L.G., Mosley-Thompson, E., Davis, M.E., Henderson, K.A., Brecher, H.H., Zagorodnov, V.S., Mashiotta, T.A., Lin, P.-N., Mikhalenko, V.N., Hardy, D.R. and Beer, J.  2002.  Kilimanjaro ice core records: Evidence of Holocene climate change in tropical Africa.  Science 298: 589-593.