BEIJING, Aug. 18 (Xinhua) -- Scientists have reconstructed a dramatic warming event that shook Earth around 300 million years ago, and their findings now serve as a stark warning about the planet's future.
An international team led by researchers from the Nanjing Institute of Geology and Palaeontology (NIGPAS) and Institute of Tibetan Plateau Research of the Chinese Academy of Sciences has pieced together this ancient hot spell, known as the Kasimovian-Gzhelian Thermal Maximum. Their study was recently published in the journal Proceedings of the National Academy of Sciences (PNAS).
At that time, Earth was in the grip of a major ice age, with massive ice sheets blanketing vast areas of land. Then, the planet warmed by about 7.5 degrees Celsius on average, while atmospheric carbon dioxide levels roughly doubled.
By analyzing fossil teeth and rocks from China and Russia, the team reconstructed changes in sea-surface temperatures. They found that the warming unfolded in two distinct phases. The first, which lasted about 60,000 years, pushed sea-surface temperatures up by roughly 2 degrees Celsius. The second, much shorter phase -- only about 35,000 years -- added another 3.5 degrees Celsius.
According to the study, volcanic eruptions set off the initial warming. But surprisingly, volcanic activity had already ceased before the main warming phase began. Instead, natural orbital cycles amplified the effect and drove the climate past a critical tipping point. Once that threshold was crossed, the Earth itself began releasing even more carbon, likely from melting permafrost, fueling abrupt and far more intense warming.
The consequences for life were severe. As oceans warmed and lost oxygen, marine ecosystems collapsed. Fossils show that tiny marine animals called conodonts became smaller and less diverse, while metazoan reefs gave way to simple macroalgal reefs, the study reports.
"The ancient Earth has shown us that once a climatic tipping point is crossed, the system can change far faster than we might expect," said Yao Le, a professor at NIGPAS. "This is not just a story of the past -- it is a cautionary tale for our own time."
Yao warns that even modest warming events in our current icehouse climate deserve our full attention. Melting ice sheets and thawing permafrost could release vast stores of carbon, which would further warm the planet, deplete oxygen in the oceans, and threaten biodiversity on a massive scale. ■
