DENVER–Tucked into a maze of federal brick buildings west of Denver, the National Ice Core Laboratory stores some of the most important data in the world.

Air bubbles trapped in the ice samples give scientists a glimpse of Earth’s climate stretching back 450,000 years. This ice is crucial, scientists say, for analyzing and addressing climate change.

“It’s incredibly important work for humanity,” said Richard Nunn, deputy curator at the lab.

He puts on clothing sufficient for an Arctic expedition and ventures into a minus 40ºF freezer where pillars of ice rest in silvery tubes stacked in rows from floor to ceiling. Nunn keeps the ice from melting, cuts it into smaller pieces, and sends ice samples to climate scientists worldwide.

During a recent visit, Nunn pulled out a tube of ice from deep under the Antarctic ice sheet. This piece of ice is 70,000 years old, he said, a relatively young specimen compared to the oldest cores in the lab dating back to 450,000 years ago. Nunn cradled the ice carefully in his hands. Each meter long specimen costs about $20,000 to extract.

The ice looks clear. But it contians microscopic bubbles of air trapped inside. These bubbles allow scientists to determine the composition of ancient climates and global temperatures. “Its the best window we have into our past,” Nunn said.

Yet U.S. politicians refuse to address or even acknowledge the reality of climate change.

The most recent United Nations-backed Intergovernmental Panel on Climate Change report anticipates a global temperature increase by 2.7ºC before 2040 –unless people shift much faster away from fossil fuels.

“It drives me crazy,” Nunn said.

At first, years ago, Nunn said he too was skeptical of anthropogenic climate change. But, after working for nearly a decade with the U.S. geological survey, he’s convinced that climate change is real and a major problem. “Anyone who has spent more than a few years studying this knows it’s cut and dry that we are causing this…..Climate change is the biggest problem of the century.”

Yet in Washington, Trump administration officials refuse to accept what a preponderance of scientists assert. “The political debate is about three steps behind,” Nunn said.

In the scientific community “the debate is about how to move forward, not if it is real,” Nunn said. “There’s a lot of money to be made in maintaining the status quo.”