Fifty-six million years ago, Earth experienced a massive, rapid spike in global temperatures.

Nature · Published 3 October 2026 Swipe more like this →

In short: The Paleocene–Eocene Thermal Maximum stands as one of the most significant climate events in recent geological history. Occurring roughly 56 million years ago, this interval saw a sudden, intense surge in global heat and carbon levels, fundamentally reshaping life on land and in the oceans for 200,000 years.

The Paleocene–Eocene Thermal Maximum, or PETM, represents a critical period of rapid environmental change. Occurring about 56 million years ago, this event is characterized by a global average temperature increase of 5 to 8 degrees Celsius. This warming pulse was driven by a massive injection of carbon into the atmosphere and oceans, a phenomenon clearly recorded in the chemical signatures of ancient marine and terrestrial fossils. Scientists track this event through a distinct negative shift in carbon isotope ratios found in sediment records across the globe, indicating a profound disruption to the Earth's carbon cycle.

Beyond the heat, the PETM triggered widespread biological upheaval. The fossil record reveals major turnovers in various species, including a mass extinction of deep-sea benthic foraminifera and the sudden appearance of modern mammal orders, such as primates, in Europe and North America. Because the early Paleogene world lacked significant polar ice sheets, the planet was already warmer than today, but the PETM pushed these conditions to an extreme. Research into this era is vital because it serves as a primary historical analogue for understanding how modern ecosystems might respond to rapid, human-driven climate change.

Current research focuses on the specific sources of this ancient carbon release and the resilience of coastal ecosystems. While some organisms failed to adapt to the shifting conditions and went extinct, others migrated or evolved. By studying fossilized molluscs and cartilaginous fish from this period, scientists aim to better predict the future of fragile marine habitats. The PETM remains a subject of intense study, not only for its own sake but as a cautionary window into the long-term consequences of rapid greenhouse gas accumulation in a world already primed for warmth.

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