Extreme cold and drought events reveal thresholds in East Asian monsoon climate
“About one fifth of the world’s population depends on the East Asian monsoon for access to fresh water,” says Francien Peterse, Professor of Organic Geochemistry at Utrecht University’s Faculty of Geosciences (Dept. of Earth Sciences) and co-author of the study. “It is therefore crucial to understand how climate change affects this monsoon system, and especially the rainfall it brings.”
Separating temperature and precipitation
It is generally assumed that, over long timescales—tens to hundreds of thousands of years—the strength of the monsoon climate tracks changes in solar radiation: the more radiation, the more intense the summer monsoon, with warmer and wetter conditions, and vice versa. However, the methods most commonly used to study the past dynamics of this system often combine temperature and precipitation signals. This makes it difficult to distinguish temperature changes from changes in rainfall.
How is climate change affecting the monsoon system and the rainfall it brings? That’s what we aim to understand
In an earlier study, the researchers therefore developed a method to distinguish past changes in temperature from changes in precipitation. They based it on subtle variations in the molecular structure of the membranes of soil bacteria. “These bacteria adjust the structure of their membrane molecules when their environment changes. The adjustments caused by temperature differ from those caused by precipitation. This allows us to distinguish between temperature and precipitation—something that conventional methods are unable to do.”
Extreme cold and drought
In the current study, the researchers analysed fossil membrane molecules in a sediment sequence from the Chinese Loess Plateau. This allowed them to investigate how precipitation responded to temperature changes over the past 250,000 years. Hao Lu, lead author of the study, says: “We see that, over astronomical timescales, both temperature and precipitation track changes in incoming solar radiation, although precipitation sometimes responds only after a delay of a few thousand years. But we also found departures from this pattern: abrupt periods of extremely cold and dry conditions that can last for several thousand years.”
Abrupt climate change on land
The researchers compared their data with climate-model output. This showed that the extreme periods occur at predictable times: when incoming solar radiation falls below a certain level. “This threshold had already been identified in a study by one of our co-authors, but now, for the first time, we have evidence that crossing it actually triggered abrupt climate change on land. We also see that the climate only recovers once incoming radiation rises above the threshold again.”
“These abrupt changes in the monsoon climate occur mainly when CO₂ concentrations are low,” Peterse says. “This shows that the background climate state matters. These ancient events do not directly predict the extremes we face today, but they help us understand how solar radiation can produce abrupt climate responses."
Journal
Communications Earth & Environment
Method of Research
Observational study
Subject of Research
Not applicable
Article Title
Extreme cold–dry events in East Asia during glacials reflect insolation thresholds
Article Publication Date
10-Nov-2026
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