The history of the world is documented and stored in a freezer at Ohio State University.

The university has a rare collection of ice cores from remote tropical glaciers that were painstakingly drilled, extracted and collected from 16 different countries. If the cores — each 4 to 5 inches across and about a yard long — were lined up they would stretch about 4.5 miles long.

But the samples are in danger of being lost. The university's freezers are past their life span, and researchers are out of room.

When Lonnie Thompson and Ellen Mosley-Thompson started collecting the cores decades ago, they measured for dust particles. As time has passed, technology has evolved. Teams from all over the world use the cores to measure for items including black carbon, bacteria and viruses.

"Everything that's in the atmosphere, it falls down with the snow and is preserved. It's frozen in time," said Thompson, a paleoclimatologist at Ohio State University's Byrd Polar Climate and Research Center.

For example, "pollen tells us about vegetation and how it's changed. We have all the thermonuclear bomb tests that humans have ever done on this Earth that have left a radioactive layer. We can measure that because we know when those tests took place, so they give us a timeline. They're really fantastic records," he said. "Unfortunately, they're disappearing."

Tropical glaciers all over the world continue to recede because of greenhouse gas emissions. That has caused rising temperatures, which makes the university's collection — kept at minus-30 degrees Fahrenheit — invaluable.

"We actually look at our projects now as salvage missions. You try to go in, you try to get the cores before they start to melt," Thompson said. That requires navigating through a myriad of red tape including the permission of countries, negotiating with local tribes in some cases and securing permits.

But the freezer rooms that contain the samples are at the end of their life span. If not replaced soon, the collection risks being damaged or lost.

"That archive is kind of like an insurance policy for the next generation of young scientists, because we're not going to be able to go out in the real world and get those samples," Thompson said. "This is the only samples that exist, once glaciers are gone." The freezer, and the facility in which it is housed, needs to be upgraded. The price is estimated at $5.5 million but the path to funding is unclear.