LONDON — The green-gold expanse of savanna; above it, the purple horizon-hiding haze; and above that, like a pyramid improbably suspended in the sky, the snows of Kilimanjaro. "Great, high and unbelievably white in the sun," as Hemingway wrote, the continent of Africa — some would say our planet itself — has hardly anything to show more fair. But the show could soon be over. The summit of Kilimanjaro is losing its ice so quickly that it could be barren dirt before the next decade is out. When the ice goes, it will take with it an irreplaceable 10-millennium record...