One of the criticisms most frequently lobbed at Al Gore's An Inconvenient Truth is that he has his facts wrong about the snows of Kilimanjaro. Yes, those immortal snows are vanishing (actually, they're glaciers, but we can blame Ernest Hemingway for that bit of poetic license), as Gore's global-warming documentary contends, but they've been receding since the early 1900s at least -- long before the planet began to warm.

Now that bit of fact-checking is looking a lot less convincing with the publication of a study on Tuesday in the Proceedings of the National Academy of Sciences. Lead author Lonnie Thompson, a glaciologist at Ohio State University who has been to the summit of Africa's tallest mountain repeatedly over more than a decade, says that while the glaciers did start melting a century ago, their retreat has sped up dramatically in recent years. "We've lost 26% of the ice since 2000 alone. And that, unfortunately, is just what we predicted would happen." Within a few decades, he says, most if not all of Kilimanjaro's glaciers will be gone.

That's not to say that Thompson's research is the final word on the debate. Indeed, glacier experts have been waging an intellectual war for years over what's really causing the ice loss atop Kilimanjaro. The simplest explanation would be that warming temperatures are making the ice melt -- and indeed, Thompson believes this is a big part of what's going on.