Earth's climate has passed through frozen epochs, greenhouse hothouses and long stretches in between. A new study argues that this history was not a random walk. Over the past 539 million years, the planet's carbon cycle and temperature tended to settle into a small set of recurring configurations, according to an international research team that includes Corinne "Cori" Myers, a paleobiologist at the University of New Mexico.
The same analysis found that when Earth shifted out of one of those configurations and into another, life on the planet was far more likely to suffer. Periods of elevated extinction — including all five of the major mass extinctions in the fossil record — clustered around those transition points rather than being spread evenly through time.
The findings appear in Nature Communications under the title "Transitions between persistent climate–carbon regimes coincide with elevated Phanerozoic biosphere vulnerability." The paper has been reviewed and fact-checked in line with the Science X editorial process, which identifies it as a peer-reviewed publication from a trusted source.
Five 'mega-climate' states across the Phanerozoic
The study focuses on the Phanerozoic Eon, the roughly 539-million-year span of Earth history during which complex life diversified and became widespread across the planet. Rather than treating the climate record as one continuous curve of rising and falling temperatures, the researchers asked whether the system spent most of its time in a limited number of preferred modes.
It did. "Our analyses identified five major 'mega-climate' states with relatively abrupt transitions," Myers said. "The behavior of CO2 and temperature in the Phanerozoic can be approximated as transitioning between these identified states."
That framing matters for how the deep past is read. A gradualist picture implies slow, incremental drift, with the planet sliding smoothly from one condition to the next. The state-based picture instead implies long stretches of relative persistence, punctuated by comparatively fast reorganizations of the climate and carbon system. Myers is an associate professor of paleobiology and paleoecology in the UNM Department of Earth and Planetary Sciences.
Why the team calls them 'Haggis bins'
The five states carry an informal nickname: the "Haggis bins." The team chose the label as a nod to Scotland, where the project began, and to the way the climate data visually separates into distinct groupings when plotted in graphical representations. The nickname is casual, but the classification behind it was not reached by eye alone — it emerged from several quantitative techniques applied to the long-term record.
Using informal shorthand for scientific regimes is common in fields that deal with sprawling datasets, where a memorable label makes it easier for collaborators to discuss patterns that are otherwise difficult to describe in a sentence. Here, the bins represent recurring combinations of carbon-cycle and temperature behavior that the planet returned to again and again.
How the researchers identified the states
To distinguish persistent regimes from ordinary variation, the team combined several analytical approaches rather than relying on a single statistical test:
- Recurrence analysis, which looks for repeated patterns in a long time series and identifies when the system revisits earlier conditions.
- Dynamical mathematical modeling, which describes how the climate and carbon system moves between states instead of drifting continuously.
- Early warning sign analysis, which searches for statistical precursors that tend to appear before a system shifts from one regime into another.
Bringing those methods together produced a picture of a climate system that lingers in a given mode and then reorganizes relatively abruptly. The authors describe the transitions as relatively abrupt rather than instantaneous, a distinction that matters when the underlying record is compressed across hundreds of millions of years.
Extinction tracks 'biosphere vulnerability'
The second half of the story concerns life. The researchers plotted macroevolutionary vulnerability against time, producing a measure in which scores greater than zero indicate that the biosphere is under stress. The five major mass extinctions all fall within that stressed region of the plot.In other words, the moments when Earth was moving between its mega-climate states are the same moments when the biological record turns grim. That association does not prove that any single climate shift caused any single extinction event, but it does show that the two phenomena occupy the same windows of Earth history with striking regularity.
The graphical summary of the work, credited to Nature Communications in 2026, shows vulnerability scores plotted alongside the five Haggis bins, rendered as grey and white bars in the background. The mass extinction events appear as skulls marking the most severe biological crises in the record.
What the study does and does not claim
The paper's central claim is descriptive and structural: CO2 and temperature behavior over the Phanerozoic can be approximated as movement among five persistent states, and elevated biosphere vulnerability coincides with the transitions. That is a different statement from saying the planet is locked into a fixed cycle or that future shifts can be scheduled in advance.
It also reframes an older assumption. Earth's climate has changed dramatically throughout its history, but the new research suggests those changes may not have been as random as previously thought. If the system tends to occupy a handful of recurring configurations, then the interesting questions become what pushes it out of one bin and what determines which bin it lands in next.
For paleobiologists and climate scientists, the work offers a shared framework. Climate researchers get a way to describe deep-time carbon and temperature behavior in terms of regimes and transitions. Biologists get a map of when the biosphere was most fragile, which can be compared against the timing of diversification, extinction and recovery in the fossil record.
Key takeaways
- An international team led by researchers including UNM paleobiologist Corinne "Cori" Myers analyzed climate and carbon behavior across the 539-million-year Phanerozoic Eon.
- The analysis identified five major "mega-climate" states with relatively abrupt transitions between them.
- Periods of elevated extinction, including all five major mass extinctions, frequently occurred as the planet moved between those states.
- Vulnerability scores above zero indicate a biosphere under stress, and the mass extinctions fall within that region of the data.
- The methods combined recurrence analysis, dynamical mathematical modeling and early warning sign analysis.
- The results were published in Nature Communications (DOI: 10.1038/s41467-026-75655-9).
The study does not close the book on why these transitions happen or how tightly climate change and extinction are coupled. But it does suggest that the planet's long-term habit is persistence followed by reorganization — and that some of the worst moments for life arrived during the reorganizations.
This article is based on reporting by Phys.org. Read the original article.
Originally published on phys.org
