Is the decline of ice on Kilimanjaro unprecedented in the Holocene?

(Review Paper) Cited in Is the decline of ice on Kilimanjaro unprecedented in the Holocene?

Points Made

The decline of ice on the glacier of Mount Kilimanjaro is occurring at a constant rate. This suggests that glaciers come and go based upon the temperature cycles of the epoch. That is, the increase and decline of glaciers is a characteristic of the Holocene, and not due exclusively to human activity and global warming.

Methods

This source is not a primary study, but rather a secondary one that compiles existing data and then theorizes based upon these collected findings. It is found that the glaciers have been declining at a constant rate since the late 19th century. The authors suggest that glacier studies be separated into slope and plateau glaciers. Other studies that find rapid decline of the Kilimanjaro glacier are only using data from the slope section of the glacier. When data from the plateau is included, then the glacier declines at a constant rate. Geothermal hot spot data is also used as an aspect of the explanation for the decline. Direct solar radiation data is also used as a part of the explanation of the decline. Air temperature is found to be relatively constant throughout the holocene, which accounts for the consistent decay. Using a mass balance model, the authors hypothesized that if a base layer of snow could be built upon over a series of a few years, the glaciers could begin to grow again.

Results

The authors concluded that the slope glaciers need to be studied independant of the summit plateau glaciers. The findings found throughout ice history research suggests that plateau ice has fluctuated throughout the Holocene, that is, preexistent to prevalent human activity. The constant nature of the plateau ice shrinkage is explained as a result of typical glacier decline in combination with the dissolution of larger ice bodies into smaller ones. Climate cycles correlate to glacier cycles, that is, a trend towards more moisture over a few seasons would allow a glacier to grow instead of decline. Ablation showed no direct causality to the fluctuation in surface area. The increase in plateau ice was found to begin in direct correlation with the end of a wet season. 165 (give or take 10) years was hypothesized to be the typical life cycle of a plateau glacier, meaning that a constant decrease in surface are is not unusual, but rather, typical.

Though the idea that global warming is simply the result of a natural cycle is plausible, never before have humans been present during this phase. As such, one can’t assume that global warming is happening independent of human interference, as the warming cycle may have been triggered or sped up as a result of human activity.