-- One ice core Thompson's team pulled hosts oblong air bubbles at the top. Those bubbles signal repeated melting and refreezing, something that fails to appear at any other point along the core, which spans 11,700 years.
-- Even during a 300-year-long drought the region experienced 4,200 years ago, the cores show no evidence of melting and refreezing during that drought.
The ice loss is bad news for Tanzania, Thompson explains in an e-mail exchange. Tanzania's main source of foreign currency is tourism. When the glacier's vanish, will the mountain still draw 30,000 to 40,000 tourists a year, as it does now? (About 10,000 a year try to climb it.) And farmers at the mountain's base rely on glacial melt water for irrigation.
"It is the balance of evidence and global nature of glacier-ice loss throughout the tropics that points to global climate change as the driver," he writes.
But what about the actions of folks at the base of the mountain? Might deforestation -- clearing trees for farmland -- have led to changes in temperatures and precipitation patterns that have at least contributed to, if not driven, changes at the summit?
After all, researchers have found that since 1971, temperatures at the base of Mt. Kilimanjaro have been rising faster than global warming alone would account for.
"We have no way of knowing how much of that, if any, is transmitted to the summit ice fields" some 15,000 feet above the base, Thompson acknowledges. You can download a full copy of the study, as a pdf, here.