A major climate tipping point occurred about 2.7 million years ago when the Northern Hemisphere ice sheets began to expand, shifting the climate from warm and stable to cold and chaotic with large millennial-scale swings.

This change set up cycles between warm interglacials and cold glacial periods, driven by gradual changes in Earth’s orbit around the Sun.

Once crossed, rapid climate variability became a built-in feature of glacial periods during the Quaternary era, spanning roughly the past 2.6 million years.

The research was led by an international team from the University of Cambridge, with sediment cores collected via the International Ocean Discovery Program and published in Science in 2026.

The findings help explain past abrupt climate shifts and enhance understanding of present-day climate risks, with the study appearing in Science.

The study aims to deepen understanding of climate variability throughout Earth’s history and its potential impact on the evolution and behavior of early humans.

Researchers analyzed deep-sea sediment cores off Portugal, examining chemical fingerprints—ratios of calcium, titanium, zirconium, and strontium—to reconstruct past climate change rates and variability over the last 5.3 million years.

A 5.3-million-year climate history from these Portugal cores is used to examine a tipping point about 2.7 million years ago.

The study uses these chemical ratios from International Ocean Discovery Program cores off Portugal to reconstruct past climate changes.

The tipping point coincides with the emergence of the Homo genus, suggesting climate swings may have influenced early human evolution.

Led by Professor David Hodell of Cambridge, the Science study links the climate shift to the rise of Homo and proposes that variability drove adaptation to changing temperatures and vegetation.

The onset of millennial-scale climate variability appears to align with early human evolution, implying climate swings helped drive adaptation.