New geological evidence suggests that the slow wobble of Earth’s axis may have triggered rapid climate swings during the Late Cretaceous greenhouse world.
When audiences watched The Day After Tomorrow, they saw a dramatic Hollywood depiction of sudden climate chaos. The film greatly compresses the timeline, but the underlying idea that Earth’s climate can change abruptly is supported by scientific evidence. During the last Ice Age, for instance, temperatures in Greenland rose by as much as 16°C (about 29°F) within just a few decades. At the same time, enormous surges of icebergs repeatedly disrupted the North Atlantic Ocean. Scientists refer to these episodes as Dansgaard–Oeschger and Heinrich events. These rapid changes, known as millennial-scale climate events, show that the climate system can reorganize much faster than would be expected from slow orbital cycles alone.
Scientists have often connected these dramatic swings to the behavior of massive ice sheets. That link has created an important question. If large ice sheets played a central role, how could similar millennial-scale climate variability occur during warm greenhouse periods of Earth’s history when such ice sheets did not exist? Researchers have struggled with this puzzle for many years.
A new study now offers an explanation. An international team led by Professor Chengshan Wang at the China University of Geosciences (Beijing) has found evidence that Earth’s precession cycles, which describe the slow wobble of the planet’s rotational axis, can generate abrupt millennial-scale climate fluctuations even when the planet is largely ice-free. The project included collaborators from Belgium, Austria, and China. Their results were published in Nature Communications.
A Window Into the Late Cretaceous
The research is based on sediment cores recovered from the Songliao Basin in northeastern China. These sediments were deposited about 83 million years ago during the Late Cretaceous. This period represents a classic greenhouse phase in Earth’s history, characterized by high atmospheric CO₂ concentrations and a lack of large ice sheets. Scientists obtained the cores through the Cretaceous Continental Scientific Drilling Project, an international program launched in 2006 by Prof. Wang.
From an astronomical perspective, Earth’s axis slowly wobbles in a motion similar to a spinning top. This movement is called axial precession, and one full cycle takes roughly 26,000 years. When this wobble interacts with the gradual shift in the orientation of Earth’s elliptical orbit, it produces two main climatic precession cycles lasting about 19,000 and 23,000 years. These cycles influence how sunlight is distributed across the planet through the seasons and play a major role in shaping long-term climate patterns.
A new study from China University explores how millennial-scale climate variability, traditionally linked to ice-sheet dynamics, occurred during warm greenhouse house periods when ice sheets were absent. Credit: Professor Chengshan Wang, from the China University of Geosciences, China
Earth’s axial tilt relative to its orbital plane (Earth’s obliquity) also affects how solar radiation is distributed across different latitudes. Regions outside the tropics receive one annual peak in solar radiation near the summer solstice in each hemisphere. Tropical regions behave differently. Because of the geometry of Earth’s tilt and orbit, solar radiation there reaches two peaks each year near the equinoxes and two minima near the solstices.
This pattern produces a distinctive structure in tropical sunlight exposure. The two annual peaks in solar radiation create four periods of maximum contrast in seasonal solar energy within a single year. Over the course of a full precession cycle, this structure leads to four separate climatic responses to changes in solar forcing driven by precession. As a result, the climate system can develop a repeating quarter-precession signal with a period of roughly 5,000 years.
Evidence From Ancient Sediments
The geological record from the Songliao Basin supports this theoretical idea. By analyzing geochemical data, mineral compositions, and simulations of bioturbation, the researchers reconstructed environmental conditions during the Late Cretaceous. Their results reveal repeated shifts between humid and arid conditions that occurred with clear periodicities of about 4,000–5,000 years.
The strength of these cycles also changed over longer time intervals. Specifically, their intensity varied with ~100,000-year cycles that correspond to changes in Earth’s orbital eccentricity.
The Late Cretaceous sediment record closely matches the predicted pattern of solar radiation changes in equatorial regions. This agreement suggests that tropical insolation can strongly influence the global climate system and may naturally trigger millennial-scale climate oscillations. Additional spectral analyses show that the ~5,000-year solar forcing cycles can lead to even faster climate shifts lasting 1,800–4,000 years. These shorter variations likely arise from nonlinear interactions within the climate system.
Together, the geological reconstructions and theoretical calculations indicate that even during warm, ice-free greenhouse climates, Earth’s climate was not stable. Instead, it repeatedly shifted between wetter and drier conditions, largely driven by solar forcing linked to orbital precession.
“During the Late Cretaceous, atmospheric CO₂ levels reached about 1,000 parts per million—comparable to projections for the end of this century,” says Prof. Michael Wagreich, a paleoclimatologist at the University of Vienna. “This makes the Cretaceous greenhouse climate a meaningful analogue for understanding Earth’s future.”
“Because Earth’s orbital configuration will remain stable for billions of years, the unveiled close link we identified between astronomical precession and millennial-scale climate cycles implies that high-frequency climate oscillations, like those seen in the Cretaceous, could also emerge in a warmer future—potentially in ways that are more predictable than previously thought,” concludes the study’s first author, Zhifeng Zhang.
Reference: “Precession-induced millennial climate cycles in greenhouse Cretaceous” by Zhifeng Zhang, Yongjian Huang, Tiantian Wang, Qiuzhen Yin, Anne-Christine Da Silva, Eun Young Lee, Hanfei Yang, Chao Ma, Hai Cheng, André Berger and Chengshan Wang, 27 November 2025, Nature Communications.
DOI: 10.1038/s41467-025-66219-4
Funding: Deep Earth Probe and Mineral Resources Exploration – National Science and Technology Major Project of China, National Natural Science Foundation of China, National Key Research and Development Program of China, Fundamental Research Funds for the Central Universities, China Postdoctoral Science Foundation, Fonds De La Recherche Scientifique – FNRS
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4 Comments
But the current “rapid rise in global temperatures” is unprecedented, according to the “settled science”.
Agreed. When I first started hearing about global warming I wondered if scientists were aware of ice ages, etc. But I now understand that a 2 -3 C rise in global temperature over just a few decade is entirely unprecedented in the history of our planet. It’s causing ice sheets to melt but is definitely not caused by them. We need to keep cause and effect clear to understand our current situation.
The claim of unprecedented warming is difficult to prove. We compare high temporal resolution and high-accuracy instrumental temperatures with proxy measurements with less than perfect correlation. Additionally, because, at best, the times of events have to be measured by methods with a constant percentage of uncertainty, and the proxy measurement may be subject to problems like diffusion of lighter isotopes or bioturbation of sediments, all measurements of geological materials tend to be similar to modern measurements that have experienced low-pass filtering. That means with dates and proxies whose values have increasing uncertainty the farther one goes back in time, peaks tend to be flattened and broadened. It is very likely that the nominal or average values reported have been smoothed by time. One should probably consider rates (or the slope of graph lines) to be a lower-bound on the actual values.
The authors spend several paragraphs reviewing the fundamentals of the Milankovitch Cycles, and then tell us that they have found that precession also “can develop a repeating quarter-precession signal with a period of roughly 5,000 years.”
After telling us how important the astronomical cycles are, they then remark that warm climates can oscillate between wet and dry climates as a result of precession, and that even warm climates are unstable.
Then they toss out a remark about about the concentration of CO2 during the Cretaceous (1,000 PPMv) and offhandedly claim that the “Cretaceous greenhouse climate [is] a meaningful analogue for understanding Earth’s future.” Considering that they are trying to convince the reader of the importance of solar input modulated by the Milankovitch Cycles, I’m surprised that it goes over their heads that they are presenting evidence to suggest that the net effect might well be that a warming planet produces more CO2 than an Ice House Earth. That is, the arrow of causation is opposite to that which is commonly assumed.