Before each trip, Putnam and his team search for locations around the globe where they know glaciers expanded during the peak of the last ice age. They find these locations by searching for moraines—landforms carved into the landscape by glaciers. Imagine setting a chunk of Play-Doh on a table and sticking your hand flatly in the center. As you add pressure, the dough under your hand sinks while the outer dough oozes up, creating a handprint. That’s similar to what happens to the earth as a glacier expands. It sits heavily on the flat ground or mountain side, pressing the surrounding landform upward, causing divots to form. Debris adds to the rising landscape with boulders and other sediments that get picked up by the glacier. When the climate warms and the glacier melts, receding from the outer edges in, these landforms remain, like the handprint in the Play-Doh. Some of the world's largest of these handprints are now called the Great Lakes.

Thousands of years later, Putnam and Strand travel to such moraines to chip samples from the rocks that remain and then use a special chemical method to determine how long ago the glacier left them where they sit today. Using this calculation and identifying the distance between the debris position and where the glacier stands now allows them to determine the rate of warming in each region in past times, as compared to today.

Collecting samples from Mongolia could reveal a lot of new information. There’s a wealth of data showing warming in the southern hemisphere in the time frame they are studying, but before Putnam and Strand’s work, very little was known about the warming patterns in the northern hemisphere. Without this information, it was difficult to know if warming and cooling occurred on a global or regional scale, compared to the current worldwide thrust of climate change.

Following the pace of climate change in the past means scientists such as Putnam can recognize and predict the accelerating pace of climate change now.

Strand believes the lack of data in the northern hemisphere could be due to the difficulties that accompany sample collection in its less accessible parts. “There is a reason that not a lot of work has been done in interior Asia—in western Mongolia,” Strand said. “A lot of the low-hanging fruit has been plucked. The glaciers of Switzerland, or the Italian Alps—you can walk out of your bed and breakfast and be on a moraine in 20 minutes. And then for lunch you can go out to a cafe and get a latte,” he said. “That is so far removed from doing fieldwork in a place like Mongolia.”