IIce core measurements are scientists’ best tool for analyzing the atmospheric changes that occurred during Earth’s recent geological history. In fact, ice cores are so central to our understanding of the planet’s changing climate that, as glaciers continue melting around the world, there’s an Ice Memory Vault in Antarctica for preserving them.
While analyzing the composition of the air bubbles trapped in these ice cores gives us a detailed snapshot of Earth’s past climate, not all atmospheric gases are easy to track. The toughest among them is hydrogen because it has a high permeability in ice, meaning it easily leaks out of ice cores and returns to the atmosphere. To create the first-ever record of historical hydrogen using ice core samples, scientists from the University of California (UC) Irvine therefore examined air bubbles in ice from Summit Station, Greenland, within 48 hours of extraction using an on-site gas chromatograph, which essentially operates like a filter separating out the different gases in a compound mixture.
The team then compared methane levels in the sample to a well-established ice core methane record and determined that their data reaches back at least 1,100 years. The results of the study were published in the journal Nature.
“We intended to extract the gas from the ice-core samples in the field and store it in flasks for later analysis in our laboratory,” UC Irvine’s John Patterson, a co-author of the study, said in a Nature research briefing. “However, after months of testing, we were unable to design a flask that could preserve the hydrogen levels…we were forced to pivot to designing, building and testing a full analytical system that we could calibrate and operate from a tent on the ice sheet.”
The results show, as predicted, that while hydrogen dipped slightly during the Little Ice Age (1500 to 1800 C.E.) by roughly 50 parts per billion, levels rose again in the northern hemisphere over the ensuing centuries from 285 parts per billion to our modern levels of 530 parts per billion. Since hydrogen is readily absorbed by soil, atmospheric hydrogen levels naturally tend to be lower in the northern hemisphere, where the the overall landmass is greater than in the southern hemisphere. The researchers propose a future ice core study in Antarctica to measure the difference in hydrogen levels between the two hemispheres in precise terms.
While understanding the levels of hydrogen in the atmosphere helps create a more complete picture of the Earth’s climate in the recent past, thankfully hydrogen isn’t a greenhouse gas—in fact it’s touted as a potential green energy solution. So you might be tempted to think there’s no need to worry about skyrocketing atmospheric hydrogen concentrations. But there’s a twist. It’s true that hydrogen doesn’t trap greenhouse gases on its own, but its interaction with other elements in the atmosphere leads to significant warming.
According to a Stanford study from December 2025, hydrogen can use up natural detergents in the atmosphere that would otherwise destroy methane. This leads to hydrogen indirectly heating the atmosphere 11 times more quickly than carbon dioxide over a century (and the ratio was over three times higher than that for the first 20 years). The study estimates that rising hydrogen levels contributed 0.02 degrees Celsius to overall warming from 2010 to 2020 alone.
Because it’s feasible to create hydrogen using renewable sources—what’s known as “green hydrogen”—it’s vital to understand hydrogen levels in the atmosphere, how it reacts with other gases, and how to curtail unwanted hydrogen from entering the atmosphere. The new ice core research underlines how drastically atmospheric hydrogen levels have already risen over the last two centuries—and how they might rise again in the future.
