Comment on "Recent glacial recession in the Rwenzori Mountains of East Africa due to rising air temperature" by Richard G. Taylor, Lucinda Mileham, Callist Tindimugaya, Abushen Majugu, Andrew Muwanga, and Bob Nakileza

Abstract

In summary, mapping of the Rwenzori glaciers is of great relevance for climate change studies of the tropics (if ice and snow are properly distinguished by the method chosen), although the analysis presented by Taylor et al. [2006] does not fully meet the required accuracy. However, the main flaw with their paper is the climate signal inferred from recent glacier recession on Rwenzori (rising Ta), due to severe deficiencies in using and interpreting climate data (see items 1-3). While rising Ta does control glacier and ice sheet retreat on a global scale, glaciers in EEA seem to behave differently [Hastenrath, 2001; Kaser et al., 2004; Mölg et al., 2003a, 2003b; Mölg and Hardy, 2004] which must not be neglected in the analysis of tropical climate change. To accurately assess the role of Ta for the mass balance of the Rwenzori glaciers, at least one of the following would be necessary. First, SEB experiments to quantify the climate sensitivity of the glaciers to Ta changes; secondly, simulations of atmospheric dynamics with a high-resolution climate model, to explore a potential link between low- and mid-tropospheric Ta on a local scale (which is possibly not resolved in the present reanalysis system). The retreat for the most recent decade reported by Taylor et al. [2006] rather indicates the continuing depletion of accumulation area and, thus, gradual vanishing of the reservoirs supplying mass to the glacier tongues. This depletion originates from a drastic moisture drop in the late 19th century [Hastenrath, 2001; Nicholson and Yin, 2001; Kaser et al., 2004; Mölg et al., 2006], and has been interrupted only by enhanced precipitation in the early 1960s which led to glacier advance, as noted in Taylor et al. [2006]. Since specific humidity seems to be a good proxy for precipitation in EEA (Figure 2) and other parts of the tropics [Bretherton et al., 2004], its decrease after ∼1970 (Figure 1c) may have accelerated the recent decline of the accumuiation areas. Still, the higher elevated glaciers on Mount Stanley will very likely outlast the next two decades forecasted by Taylor et al. [2006], since they show a much slower decrease than the other glaciers on Rwenzori (Table 1). Copyright 2006 by the American Geophysical Union.