An ancient climate tipping point is revealed in new fossils dating back to Earth’s most severe extinction event, often referred to as the “Great Dying,” as tropical forests disappeared due to long-term global warming.
The catastrophe, known as the Permian-Triassic Extinction, occurred 252 million years ago, wiping out entire species of plant and animal life from both the sea and land. The new work, led by the University of Leeds and the China University of Geosciences in Wuhan, analyses the fossil record to develop an entirely new theory of how runaway greenhouse conditions developed past a climate tipping point.
Warming without End
Prior research suggested that the Siberian Traps, a large volcanic region in present-day Russia, were responsible for the five-million-year warming period. Yet the reason for the warming’s extreme duration remained elusive.
The new research finally presents an answer to this extended delay in recovery. They propose that the deaths of tropical forests severely inhibited the planet’s ability to absorb carbon, leaving greenhouse gases in the atmosphere for longer.
“The causes of such extreme warming during this event have been long discussed, as the level of warming is far beyond any other event,” said lead author Dr Zhen Xu, from the School of Earth and Environment, University of Leeds. Critically, this is the only high-temperature event in Earth’s history in which the tropical forest biosphere collapses, which drove our initial hypothesis.
“Now, after years of fieldwork, analysis and simulations, we finally have the data which supports it,” Zu said.
Investigating the Fossil Record
A new fossil analysis method, combined with climate data extracted from rock formations, allowed the team to produce maps illustrating plant productivity over time. Their findings showed that as vegetation loss persisted, carbon dioxide remained in the air instead of being sequestered in plant life.
Long-term Chinese research on Permian-Triassic fossils was essential to the study, as the country holds the most extensive geological record of the period, in addition to having a history of comprehensive research in the field. Zhen’s work builds on that of his co-authors, Professor Hongfu Yin and Professor Jianxin Yu, who have collected the fossils for almost a decade, traveling across China to areas so remote the pair could only reach them by horse or boat.
In 2020, Zhen began working at the University of Leeds alongside Professor Benjamin Mills, producing simulations of the Permian-Triassic Extinction, with a particular focus on the interplay between climate and tropical vegetation loss. Their simulations confirmed that the reduction in vegetation displayed in the fossil record matches the degree of warming.
“Paleontology needs to embrace new techniques—from numerical modelling to interdisciplinary collaboration—to decode the past and safeguard the future,” explained Professor Yin.
Reaching a Tipping Point
Although not all climatologists are fond of the idea of a “tipping point,” Xu’s work demonstrates that at a certain threshold, climate change can become a runaway process. When the warming became too severe for plant life, the last vanguard against warming was eradicated.
“There is a warning here about the importance of Earth’s present-day tropical forests,” Professor Mills added. “If rapid warming causes them to collapse in a similar manner, then we should not expect our climate to cool to preindustrial levels even if we stop emitting CO2,” Professor Mills said.
“Indeed, warming could continue to accelerate in this case even if we reach zero human emissions. We will have fundamentally changed the carbon cycle in a way that can take geological timescales to recover, which has happened in Earth’s past,” Mills said.
“Let’s make sure our work transcends academia: it is a responsibility to all life on Earth, today and beyond,” Yu said.
“Earth’s story is still being written, and we all have a role in shaping its next chapter.”
The paper “Early Triassic Super-Greenhouse Climate Driven by Vegetation Collapse” appeared on July 2, 2025, in Nature Communications.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.