>> Ice cores are about as close as you can get today to a time machine. Imagine being able to go back in time to any year that you wanted. To be in a position to reconstruct what the atmosphere was like, what the plant life might have been like at that time, what the ocean communities were like. The Greenland Ice core record is a very unique record. It provides us with the longest history of climate from an ice core that we can get in the Northern Hemisphere. >> This Greenland ice core was collected from 1989 to 1993, working about five months during the summer. We drilled 24 hours a day. Once the samples, the cores, came out of the drill hole, we lowered them down into this underground lab we had up in Greenland. We need to keep the ice core below minus 20 degrees Centigrade in order to contain the history that's in the ice core. >> How cold is it in the freezer? >> It's about minus 20 degrees Centigrade. >> Oh, cold enough. >> Cold enough. These ice cores are from a bunch of different places. Antarctica, Greenland, the Canadian islands, the northern Canadian island, the Himalayas. And one of the first things we'll do is we'll look at the ice core and we'll look at what we can actually see in the ice core just by shining light from behind. We can see different annual layers, such as here, and here, and here from the difference in the crystal size between summer and winter. So we can count annual layers back just like you would in a tree ring core. The Greenland ice core record is annually dated to about a 110,000 years. This piece of ice core represents probably about five years, at the depth that it's at. After we get a quick look-see at the ice core here, what we'll do is we'll take it onto the saw, and we'll slice it into various different sizes depending upon the work we want to do on the ice core. For the chemical work, we'll take it and slice it into little sections, and then take that upstairs to our other freezers, and either melt it or scrape it to get a good chemistry sample. Not only do the crystals' sizes change from year to year, but the chemistry changes between summer and winter. >> This is the laboratory in which we analyze the melted samples from the ice core. We get measurements of the major chemical species in the atmosphere: calcium, magnesium, sodium and chloride. >> What other kinds of records do you compare the data from the Greenland ice core in order to understand the history of global climate? >> We compare the ice core records to a variety of other paleoclimate records that come from marine environments, sediments, from lake sediments, from tree rings, from cave deposits. There are a tremendous number of records that we can use to try and understand the global climate. >> One of the ultimate goals of all paleoclimate programs is to be able to understand how climate has changed over the past, >> To be able to assess where we are in the climate system today, and to be able to make good predictions about climate in the future.