How does global warming lead to an ice age?

Researchers working at the Riverside campus of the University of California have scientifically explained why global warming can unexpectedly lead to the ice age. Scientists have identified an important link in the Earth's carbon cycle, which was previously not sufficiently considered. This very factor explains why ancient glacial periods were so intense and difficult. The research results were published in the journal "Science."

Previously, scientists believed that climate is mainly stabilized through natural weathering of rocks. Rain absorbs atmospheric carbon dioxide and falls on land, water destroys silicate rocks and carries the bound CO2 to the oceans. There, carbon combines with calcium to form shells and layers of limestone and persists for millions of years. This process gradually reduces the amount of CO2 in the atmosphere.

Geologist Andy Ridgewell noted that as the planet warms up, this process accelerates and more carbon is absorbed, as a result of which the Earth begins to cool again. Previously, this system was assessed as maintaining a smooth and stable climate. However, geological evidence shows that some glacial periods covered almost the entire Earth with ice and snow. This situation cannot be explained solely by the mechanism of "soft" regulation.

Researchers discovered an additional process that intensifies carbon burial in the ocean. When the temperature rises, precipitation brings more nutrients, such as phosphorus, into the ocean. This leads to a sharp increase in plankton that absorbs CO2 through photosynthesis. When plankton dies, it sinks to the ocean floor and carries a large amount of carbon with it.

In hot conditions, this system becomes even more complex. Excessive growth of plankton reduces oxygen in the ocean. Oxygen deficiency leads to phosphorus returning to water instead of precipitating. This stimulates the growth of new plankton and intensifies the cycling process. As a result, very large volumes of carbon could be buried, and global temperature could drop sharply.

Ridgewell compares this situation to an air conditioning system: it usually stabilizes the temperature, but in some cases can lead to sharp cooling. Computer models have also shown that this feedback is strong enough to start the ice age.

Scientists note that in ancient times, the climate system operated very stably due to the low oxygen content in the atmosphere. Currently, oxygen levels are quite high, so future cooling processes may not be as intense as they were back then. Nevertheless, it is quite possible that this mechanism will accelerate the beginning of the next glacial period.

Experts note that this fact should not reassure people. Because the next ice age may begin in hundreds of thousands of years, but the current global warming remains the biggest problem for today's generation.

Aziza Shukhratova

Editor of «ZAMIN.UZ»