This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: "Sediment and fossil records are a major pillar of our understanding of how the climate works—but climate scientists have gotten something wrong about Australia's ice age," says Dr. Wall, lead author of a new research paper published in Quaternary Science Reviews.
"Experts tend to think of the last ice age as having less complex rainfall patterns than today. Our new research suggests that narrative may have arisen from what the past can't tell us, rather than what it can." The new study analyzes 69 natural paleoenvironmental archives from tropical Australia spanning the past 130,000 years, with no published hydrological records of sub-decadal resolution before 1,900 years ago. Changes in water availability are frequently invoked to explain past changes in humans, flora, fauna and fire behavior, especially regarding the transition from the Late Pleistocene to the more complex Holocene.
"Technically, we're still in the ice age, just in a relatively warm and wet period called an interglacial," Wall explains. "The last time Earth was wetter than today was a period from 130,000 to 115,000 years ago: the Last Interglacial, which is of great interest to climate scientists because it is also the last time Earth was warmer than today. This makes it a good analog for future climate change." Scientists have suggested that rainfall patterns were simpler in the past, then became patchier, less reliable and more complex in the past 12,000 years.
Wall suggests that seeming complexity is a result of bias and says the research team found no support for the previous hypothesis that the Holocene is uniquely hydrologically heterogeneous. They instead suggest the trend of reduced resolution in the past could be mistaken for greater simplicity. "Characterizing the Holocene as a period of uniquely erratic rainfall has significant implications for interpreting past human and environmental responses to climate change.
Reconstructions from further back in time tend to be poorer quality, which must be considered when comparing records," Wall says. "Taking a look at the bigger picture, we found that rainfall during the Last Interglacial and today looks pretty indistinguishable. Unfortunately, that may mean that a warming climate might be even less predictable than we had assumed.
"To understand how any region fits into the greater climate system, Quaternary science must be explicit about what can and cannot be determined from the available data." Alexander F. Wall et al, Hydroclimate complexity across the last glacial cycle in tropical Australia: reassessing the uniqueness of the Holocene, Quaternary Science Reviews (2026). DOI: 10.1016/j.quascirev.2026.110253 Journal information: Quaternary Science Reviews BSc Life Sciences & Ecology.
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