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539 million years of climate boiled down to five settings

Qurexa Editorial Team24 September 20265 min read 0 0
539 million years of climate boiled down to five settings

What happened

Earth's climate has swung wildly over its history. There have been times when forests grew near the poles and times when ice reached far towards the equator. You might expect that history to look like a long, messy squiggle. A new study says it does not. It looks more like a light switch with five settings. An international research team examined the last 539 million years, a stretch geologists call the Phanerozoic. That is roughly the period since animals with hard shells and skeletons appeared, and it is the part of Earth's history with the best fossil and chemical record. They combined records of temperature and of the carbon cycle, and looked for patterns. What they found is that the climate did not drift smoothly. It settled into a small number of long-lived, stable states, sat in each of them for a long time, and then shifted relatively quickly to another. Five such states covered the whole period. Then they lined those shifts up against the fossil record of extinction. The pattern was clear: periods of elevated extinction, including the five great mass extinctions, clustered around the transitions between states rather than during the stable stretches. The paper, 'Transitions between persistent climate-carbon regimes coincide with elevated Phanerozoic biosphere vulnerability', was published in Nature Communications and reported on 23 September 2026. Palaeobiologist Corinne Myers of the University of New Mexico was among the authors.

Why this matters

The usual way we talk about climate and extinction is in terms of how hot or cold it got. This study suggests the more dangerous thing is change itself. Life adapts. Given long enough, organisms evolve to suit hot worlds and cold worlds alike. Some of Earth's warmest periods were also extremely rich in species. What life handles badly is being moved quickly from one set of conditions to another. That has a sobering relevance to now. The concern about modern climate change has never mainly been about the absolute temperature. It is about the speed. Changes that took tens of thousands of years in the geological past are being compressed into decades. The study also reframes 'stability'. A climate that stays put for tens of millions of years is not stable because nothing is happening. It is stable because feedbacks in the carbon cycle, the oceans and the rocks keep pulling it back. Systems like that tend to resist change up to a point, then move fast when that point is passed. That is a well-known behaviour in many natural systems, and it is not a comforting one.

What the evidence actually says

It is worth being honest about how hard this kind of research is. Nobody had a thermometer 400 million years ago. Temperature has to be reconstructed indirectly, from the chemistry of fossil shells, from ancient soils, from oxygen isotopes in rock. Each method has its own assumptions and its own error bars, and the further back you go, the wider those bars get. The fossil record is also uneven. Some periods and some places are far better preserved than others. Apparent spikes in extinction can partly reflect where the rocks happen to be good. The researchers are working with these limits, not around them, and the value of the study is in the pattern rather than any single date. The finding that extinction clusters at transitions holds up across the record rather than depending on one event. There is also a genuine chicken-and-egg question. Some of the transitions were probably triggered by the same events that killed things directly, such as enormous volcanic eruptions. In those cases the climate shift and the extinction share a cause, rather than one causing the other. The study identifies a consistent association; it does not settle the mechanism in every case. What it does establish is that Earth's climate system has preferred resting places, that it moves between them rather than drifting, and that life has repeatedly struggled during the moves.

Practical advice

This is deep history, but there are a few sensible ways to handle news like it. Be careful with comparisons between ancient warm periods and today. You will sometimes see 'the Earth has been much hotter before, so this is nothing new'. The study is a good answer to that. Life did fine in hot worlds it had millions of years to adjust to. The risk sits in how fast things move. When you read about extinction rates, look for whether the authors discuss how patchy the fossil record is. Good papers say so openly. This one does. If you want reliable UK information on what climate change means locally, the Met Office publishes free regional projections and explainers, and the Environment Agency publishes flood risk information for individual postcodes. And if you have children studying geography or science, the five-states idea is a genuinely useful mental picture: natural systems often resist change, then shift quickly once pushed past a limit. It applies far beyond climate.

What to know

Researchers analysing 539 million years of temperature and carbon-cycle records found that Earth's climate occupied only five long-lived states in all that time, and that elevated extinction, including the five great mass extinctions, clustered around the transitions between them. The practical message is about rate, not just temperature. Life has thrived in hot worlds and cold worlds. It has repeatedly suffered when conditions changed quickly. Reconstructing ancient climate is difficult and the uncertainties are large, so the strength of the work is in a repeated pattern rather than in precise dates. It is a long, slow record with a fairly short lesson attached. Sources: Nature Communications, 'Transitions between persistent climate-carbon regimes coincide with elevated Phanerozoic biosphere vulnerability', 2026, https://www.nature.com/articles/s41467-026-75655-9 ; Phys.org, 'Earth shifted among five mega-climate states over 539 million years, with extinctions spiking near transitions', 23 September 2026, https://phys.org/news/2026-09-earth-shifted-mega-climate-states.html ; University of New Mexico Newsroom, 'UNM researcher helps uncover recurring climate regimes linked to elevated extinction risk', September 2026, https://news.unm.edu/news/unm-researcher-helps-uncover-recurring-climate-regimes-linked-to-elevated-extinction-risk This article is for general information and does not replace advice from a doctor, pharmacist or other qualified healthcare professional.

#climate history#mass extinction#geology#carbon cycle#Nature Communications#palaeoclimate

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