Cores extracted from the ice fields of Africa's Mount Kilimanjaro are yielding clues about past climate in the region and, together with recent data, helping to forecast the future of the mountain's glaciers. According to a report published today in the journal Science, between 11,000 and 4,000 years ago, the region was generally warmer and wetter than it is today but experienced three major droughts in that time period. In addition, the scientists suspect that Kilimanjaro's ice cover could disappear by 2020 if current climate conditions persist.
Lonnie G. Thompson of Ohio State University and his colleagues collected six ice cores from Africa's highest peak in 2000. The team found that the area surrounding the mountain 9,500 years ago differed significantly from today's landscape. For one, the nearby Lake Chad--which at 17,000 square kilometers is Africa's fourth-largest water body--used to cover 350,000 square kilometers. The researchers also found that methane levels in the core dropped dramatically in the section corresponding to approximately 8,300 years ago. Because methane emissions are tied to the amount of wetlands in a given region, Thompson says that "We believe that this represents a time when the lakes of Africa were drying up." And around 4,000 years ago, the scientists surmise, the region underwent a 300-year drought. This finding meshes well with historical records that discuss a massive drought that hit the Egyptian empire.
The new results represent the first ice core data retrieved from Africa and as such they provide important historical context for climate change in the region. In order to understand the current state of Kilimanjaro's glaciers, the investigators have started collecting continuous data from a mountaintop weather station. So far, they have documented a one-meter retreat by the glacier and a loss of one meter of thickness in the last two and a half years. What is more, maps, aerial photographs and satellite pictures indicate that 80 percent of the ice has disappeared between 1912 and 2000. If the melting continues at this rate, the scientists predict that the snows of Kilimanjaro could vanish within 20 years.