Learn how plants respond to higher atmospheric CO2 concentrations

How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

The Glaciers of Kilimanjaro
Volume 14, Number 2: 12 January 2011

In the introduction to their newest study of the ice fields atop Kibo (Kilimanjaro's highest peak), Kaser et al. (2010) write that these frozen features have garnered "particular attention," ever since Irion (2001) attributed modern changes in them to "increased air temperature in the context of global warming," and since Thompson et al. (2002) reported on what they described as the "near extinction of the ice on Kibo," which they characterized as being "unprecedented over the last 11,700 years." Shortly thereafter, however, Kaser et al. (2004) developed an alternative hypothesis, namely, that atmospheric moisture primarily controls the modern-time glacier changes on Kibo, as Kaser et al. (2010) indicate is also suggested by the work of Molg and Hardy (2004), Cullen et al. (2006, 2007) and Molg et al. (2003, 2006, 2009a,b), which finding, in their words, "not only rules out rising local air temperature (i.e. on the peak of Kibo) as the main driver of observed changes during the last 120 years, but also puts the currently accepted 11,700 years age in question."

Based on their review of a compilation of all available information on present-day phenomena that control the glaciers on Kilimanjaro, and after what the five researchers describe as "a careful glaciological evaluation," Kaser et al. (2010) conclude that "minor changes in thickness have no impact on the changing surface area of the tabular plateau glaciers," while noting that "plateau glacier area decrease has been strikingly constant over the twentieth century," and that "ablation rates of the ice walls are [also] persistently constant." In addition, their analyses suggest that the mountain's plateau ice "may have come and gone repeatedly throughout the Holocene," and that the reduction of plateau ice in modern times "is controlled by the absence of sustained regional wet periods rather than changes in local air temperature on the peak of Kilimanjaro."

Clearly, one cannot be so glib as U.S. Senator John McCain was on the floor of the U.S. Senate back in 2004, when he described his affection for Ernest Hemingway's famous short story "The Snows of Kilimanjaro" and went on to attribute the decline of glacial 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." Quite to the contrary, there are many researchers who have devoted the better parts of their scientific careers to studying this subject who openly reject McCain's misguided view, as well as that of then-Senator Hillary Clinton, who at the same hearing as McCain displayed a set of photos taken from the same vantage point in 1970 and 1999 and said that in those pictures "we have evidence in the most dramatic way possible of the effects of 29 years of global warming."

Unfortunately (for the two political luminaries), the detailed measurements and analyses that are described in the research papers cited by Kaser et al. (2010) provide no support whatsoever for McCain's and Clinton's contentions, just as Kaser et al.'s own work provide no support for them.

Sherwood, Keith and Craig Idso

Cullen, N.J., Molg, T., Hardy, D.R., Steffen, K. and Kaser, G. 2007. Energy-balance model validation on the top of Kilimanjaro, Tanzania, using eddy covariance data. Annals of Glaciology 46: 227-233.

Cullen, N.J., Molg, T., Kaser, G., Hussein, K., Steffen, K. and Hardy, D.R. 2006. Kilimanjaro: Recent areal extent from satellite data and new interpretation of observed 20th century retreat rates. Geophysical Research Letters 33: 10.1029/2006GL0227084.

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

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.

Kaser, G., Molg, T., Cullen, N.J., Hardy, D.R. and Winkler, M. 2010. Is the decline of ice on Kilimanjaro unprecedented in the Holocene? The Holocene 20: 1079-1091.

Molg, T., Chiang, J.C.H., Gohm, A. and Cullen, N.J. 2009a. Temporal precipitation variability versus altitude on a tropical high mountain: Observations and mesoscale atmospheric modeling. Quarterly Journal of the Royal Meteorological Society 135: 1439-1455.

Molg, T., Cullen, N.J., Hardy, D.R., Winkler, M. and Kaser, G. 2009b. Quantifying climate change in the tropical mid-troposphere over East Africa from glacier shrinkage on Kilimanjaro. Journal of Climate 22: 4162-4181.

Molg, T. and Hardy, D.R. 2004. Ablation and associated energy balance of a horizontal glacier surface on Kilimanjaro. Journal of Geophysical Research 109: 1-13.

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.

Molg, T., Renold, M., Vuille, M., Cullen, N.J., Stocker, T.F. and Kaser, G. 2006. Indian Ocean zonal mode activity in a multi-century integration of a coupled AOGCM consistent with climate proxy data. Geophysical Research Letters 33: 10.1029/2006GL026384.

Thompson, L.G., Mosely-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.