Alarming speed: CO2 increase outpaces last 50,000 years, ice cores reveal

Arctic ice is revealing more secrets. As it has accumulated over hundreds of thousands of years, it serves as a kind of time capsule that documents the changes occurring on Earth. This also applies to fluctuations in carbon dioxide levels. The ability to check how they have been shaped over the last 50,000 years leads to alarming conclusions.

Researchers from Oregon State University, based on an analysis of Antarctic ice, concluded that the level of carbon dioxide in the atmosphere is increasing ten times faster than during the last 50,000 years.

By examining an ice core extracted from a depth of about 3.2 kilometres, scientists have been able to reconstruct changes in the composition of the Earth's atmosphere over the last several tens of thousands of years.

One of the most important discoveries is the confirmation that although there have been fluctuations in the carbon dioxide level in the past, and an increase has been observed for millennia, the changes have never been as rapid as they are now.

The fastest observed changes were about 14 parts per million (ppm) fluctuations over 55 years. These occurred thousands of years ago during one of the so-called Heinrich Events (H4). At that time, large masses of ice detached from the glaciers in the Northern Hemisphere, drifting and melting in the ocean, changing global water circulation and causing climate changes.

Currently, an increase in this value is recorded every 5-6 years. This represents a tenfold acceleration compared to the period when changes were most dynamic in the past.

How does studying ice give us knowledge about climate in the distant past? Paleoclimatic studies take advantage of the fact that in Antarctica, there are places where the temperature has not risen above 0 degrees Celsius for hundreds of thousands of years. The oldest samples taken are 2.7 million years old, and preserved deposits of ancient ice allow for uninterrupted measurements over the last 800,000 years.

However, such places are very rare—the lowest layers are melted by heat from inside the Earth, and masses of ice are constantly moving. For this reason, only about 1.67 percent of the Antarctic ice sheet surface is suitable for paleoclimatic research. The most valuable is glacial blue ice, the oldest ice from deep within the ice sheet.

Ice cores are extracted from these places after boreholes are made several kilometres deep. They contain air bubbles trapped continuously in the ice from when it was on the surface.

Thanks to preserved air samples, mass spectrometry can reconstruct the composition of the atmosphere from the very distant past, including determining the concentration of greenhouse gases such as carbon dioxide. This method also allows for assessing volcanic activity or the occurrence of significant cataclysms, among other things.

The data obtained from ice cores are alarming in conjunction with current measurements. Continuous measurements, which have been conducted since 1958 at the research station on Mauna Loa in Hawaii, prove that the last few years have set records not only in terms of CO2 concentration in the atmosphere but also in the pace of its increase.

In 2023, the Mauna Loa reading indicated 421 ppm, and two years earlier, 419 ppm. This year, 426 ppm was recorded. Although these fluctuations can be partially explained by the El Niño phenomenon (a periodic increase in water temperature around the equator), the accelerating climate changes already affect 3.6 billion people, according to the current IPCC report (Intergovernmental Panel on Climate Change).

These changes also affect air movements, creating increasingly westerly solid winds in the Southern Hemisphere. These phenomena, which influence water circulation in the ocean, further intensify the observed climate changes, limiting the ocean's ability to absorb CO2.