Climate snapshots trapped in ancient ice tell a surprising story

Eric W.

Wolff is in the Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK.

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Over the past three million years, global climate patterns have undergone two key temporal shifts.

About 2.6 million years ago, ice sheets formed over the Northern Hemisphere at high latitudes, waxing and waning in 40,000-year cycles.

Then, around one million years ago, during a time interval called the Mid-Pleistocene Transition (MPT) that cycle period increased to around 100,000 years, allowing ice sheets to grow larger.

Now, two papers in Nature ( Marks-Peterson et al .

1 and Shackleton et al .

2 ) explore the MPT using ice cores that have a highly disrupted structure, including non-chronological layering of ice that formed at different times.

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doi: https://doi.org/10.1038/d41586-026-00636-3
Marks-Peterson, J.

et al.

Nature 651 , 647–652 (2026).

Shackleton, S.

et al.

Nature 651 , 653–657 (2026).

Jouzel, J.

et al.

Science 317 , 793–796 (2007).

Lüthi, D.

et al.

Nature 453 , 379–382 (2008).

Bereiter, B.

et al.

Geophys.

Res.

Lett.

42 , 542–549 (2015).

Willeit, M., Ganopolski, A., Calov, R.

& Brovkin, V.

Sci.

Adv.

5 , eaav7337 (2019).

Clark, P.

U., Shakun, J.

D., Rosenthal, Y., Köhler, P.

& Bartlein, P.

J.

Science 383 , 884–890 (2024).

Clark, P.

U.

et al.

Science 390 , eadv8389 (2025).

Rae, J.

W.

B.

et al.

Annu.

Rev.

Earth Planet.

Sci.

49 , 609–641 (2021).

The author declares no competing interests.

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