Dried-out leaf hints of global warming.

• Position: Glaciers

Less than 20 miles from the site where melting ice exposed the 5,000-year-old body of Otzi the Iceman, scientists have discovered new and compelling evidence that the Italian Alps are warming at an unprecedented rate. Part of that evidence comes in the form of a single dried-out leaf from a larch tree that grew thousands of years ago.

A six-nation team of glaciologists drilled a set of ice cores from atop Mt. Ortles in northern Italy and described their early findings at the annual American Geophysical Union meeting in San Francisco, Calif.

The Alto dell'Ortles glacier, which did not show signs of melting for thousands of years, now appears to be shifting away from a constantly below-freezing state to one where its upper layers are at the melting point throughout the year, says project leader Paolo Gabrielli, research scientist at Byrd Polar Research Center, Columbus, Ohio. "Our first results indicate that the current atmospheric warming at high elevation in the Alps is outside the normal cold range held for millennia. This is consistent with the rapid, ongoing shrinking of glaciers at high elevation in this area."

As they drilled into the glacier in 2011, Gabrielli and his team discovered that the first 100 feet was composed of "firn"--grainy, compacted snow that...