 My name is Peter Griffith and I'm an Earth scientist at NASA Goddard Space Flight Center in Greenbelt, Maryland. We study our living Earth from leaf to orbit so we can provide the best scientific information about the consequences of a changing planet to society. Normally at this time of year, I'd be planning an expedition to Alaska and Northern Canada as part of a project called the Arctic Boreal Vulnerability Experiment, or above for short. For the past month, I've been very busy working from home, replanning the airborne remote sensing campaign that we had intended to conduct from June through August. That's not going to happen this year. However, I can take you to some field sites near Fairbanks, Alaska, where we and our partner agencies are conducting research on falling permafrost. Join me now as I step back in time to enter the U.S. Army Corps of Engineers' permafrost tunnel. We're walking into the tunnel on a warm summer day, dressed for the cold we'll find inside. The first thing I notice is the noise of the fans and compressors that keep the interior air below freezing so that the tunnel doesn't melt and collapse. I gotta admit, this always makes me think of the scene in Star Wars, The Empire Strikes Back, when C-3PO scolds R2-D2 for flooding Princess Leia's room in the ice caverns where the rebels are hiding out, because R2-D2 had raised the air temperature to make her more comfortable. Anyway, it's quite cold inside. It's also dusty. The ice in the permafrost sublimates directly from solid to water vapor, leaving a fine dust on the walls and floors and ceiling that every movement disturbs. Oddly enough, the central and northern parts of Alaska were not covered in glaciers during the ice ages. In the summertime, this region was wet and green and covered with animals. And we're walking through the frozen remains of these ice age plants and animals. And we can see them in the walls and ceilings. We're seeing pieces of willow shrubs and birch and older trees and also grasses that are common today in wet lowlands. Here's our guide, Dr. Matthew Sturm from the University of Alaska Fairbanks, showing us an example of grass that was carbon dated to 32,000 years old. It's a really remarkable specimen because it's still green. In this case, the grass collapsed into a melting ice wedge in late summer and froze before it could rot. Speaking of rot that I mentioned the smell, the whole tunnel smells like recently decomposed vegetation. Even though the vegetation is tens of thousands of years old, now that it's exposed to the air and to microbial degradation, it starts to smell. It's not entirely unpleasant. It's sort of a combination of freshly mowed grass and cut trees. There you can see Matt brushing some of the silt off of the walls. Now that we're leaving the tunnel, let me show you some of my permafrost treasures. This is a 40,000 year old plant root that came out of a section of the tunnel that was being recently excavated. When I picked this up, it reeked of resin. It smelled like a fresh cut piece of pine. This came out of a hillside near the permafrost tunnel that was collapsing. This is the tooth of a steppe bison. This is an extinct bison that once roamed interior Alaska during the ice ages. This is probably my favorite. This is a fragment of the tooth of a woolly mammoth. It was also full of all sorts of mud and goo. It doesn't stink anymore, but it's been on my shelf for several years now. Across the Arctic, permafrost contains ancient frozen organic material, like what you saw today in the permafrost tunnel. As the Arctic warms, the permafrost is thawing and this organic matter is decaying, releasing the greenhouse gas, carbon dioxide, and also methane. NASA and our partners are studying how much CO2 and methane are coming out of the thawing permafrost to improve our climate models. To find out more, visit climate.nasa.gov.