University of Washington researchers have discovered that Kilimanjaro's snowcap began retreating before the measurable rise of global warming in the 1970s.
Kilimanjaro's 4-mile-high summit never goes above freezing. Researchers believe snow loss here is due instead to a lack of snowfall and sublimation (a type of evaporation). Most other glaciers are more directly affected by rising temperatures.
The current dry period began well before humans began pumping significant amounts of carbon dioxide into the atmosphere. In this case, global warming may only be contributing to a pre-existing situation.