In May and June 2007, Mary Albert (CRREL) and Jeff Severinghaus (Scripps) led a team of 9 researchers and 3 drillers in a 3-week project to drill down through nearly 125 meters of "firn" and ice close to NSF's Summit Station, Greenland. "Firn" is multi-year snow before it's transformed into solid ice through the pressure of layer upon layer of new snow each successive year. Understanding the physical structure of the firn and the gases trapped in it, is essential to properly interpreting the ice core record, and understanding what cores reveal about Earth's past climate. As Jeff Severinghaus says, with a more accurate understanding of snow, firn and ice you can take climate data from ice cores "to the bank" - such as the fact that sometimes Earth's climate can jump 18 degrees F in just a decade - and make more accurate predictions of the future.