UNM researcher helps uncover recurring climate regimes linked to elevated extinction risk

Earth's climate has undergone dramatic changes throughout its history, but new research suggests those changes may not have been as random as previously thought.

A study led by an international team of researchers, including The University of New Mexico paleobiologist Corinne "Cori" Myers, found that Earth's climate over the past 539 million years tended to remain within a small number of recurring climate states. The research also found that periods of elevated extinction, including the five major mass extinction events in Earth's history, frequently occurred as the planet transitioned between those states.

The findings were published in Nature Communications in a paper titled "Transitions between persistent climate-carbon regimes coincide with elevated Phanerozoic biosphere vulnerability."

The Phanerozoic Eon spans approximately the last 539 million years and includes the period during which complex life diversified and became widespread on Earth.

"Our analyses identified five major 'mega-climate' states with relatively abrupt transitions," said Myers, an associate professor of paleobiology and paleoecology in the UNM Department of Earth and Planetary Sciences. "The behavior of CO2 and temperature in the Phanerozoic can be approximated as transitioning between these identified states."

The research team informally referred to the five climate states as "Haggis bins," a nod to the Scottish setting where the project began and the appearance of the climate data in graphical representations.

To identify these climate states, the researchers used several analytical approaches, including recurrence analysis, dynamical mathematical modeling and early warning sign analysis. They combined those techniques with data on extinction and biodiversity to examine relationships between long-term climate patterns and changes in the biosphere.

In simple terms, the researchers analyzed hundreds of millions of years of climate data to determine whether Earth's climate behaved more like a system moving randomly through different conditions or one that repeatedly settled into recognizable patterns.

The analysis indicated that climate conditions tended to remain within relatively persistent regimes before undergoing transitions to another state. Those transitions were associated with periods of increased extinction.

The researchers found that elevated extinction rates, including those associated with the "Big Five" mass extinctions, tended to occur near transitions between the major climate states. The team's early warning sign analysis also provided evidence of increasing instability within the climate data around these transitions.

The study further examined what the researchers call "biosphere vulnerability" essentially, how readily biodiversity can decline when extinction rates outpace the rate at which new species arise.

"Biosphere vulnerability overall was higher for nearly all periods of elevated extinction and particularly high at the Big Five mass extinctions," Myers said.

The project grew out of a two-week workshop in summer 2024 at the Futures Institute, part of the International Centre for Mathematical Sciences at the University of Edinburgh in Scotland. Five researchers from different scientific backgrounds, including mathematics, climate modeling and paleobiology, came together to examine mass extinctions in the context of global climate change.

Myers' laboratory at UNM played a central role in providing the underlying data used in the study. Her lab has spent nearly a decade compiling climate proxy data and developing methods for estimating extinction rates. Several former UNM graduate students contributed to collecting portions of that data as part of their graduate research.

"My role in the project was conceptualizing the project with collaborators, providing all the data, and assisting in both analysis and publication of results," Myers said.

Understanding what happens during transitions between those regimes could provide new insight into why ecosystems become more vulnerable to extinction.

"Future work should target Haggis bin transitions to help pinpoint the nature of increased stress these transitions place on the biosphere," Myers said.

Myers also emphasized the importance of continuing to study environmental change occurring today and what it could mean for modern ecosystems.

While the study examines climate and biodiversity across hundreds of millions of years rather than explicitly predicting future extinction potential, its findings provide new perspective for considering how changes in the climate system can affect the biosphere.

The research has particular relevance for places such as New Mexico, where a naturally arid environment makes water availability especially important as climate conditions change.

Myers presented the research in May at the Rocky Mountain Section meeting of the Geological Society of America in Albuquerque. She is scheduled to present the findings again at the Geological Society of America's annual meeting in Denver in October.