How 17th century climate change may have doomed a Tibetan kingdom
- The state of Guge was defeated by a neighbouring realm, but scientists say environmental factors may have caused the society to collapse
- Researchers found that temperatures on the Tibetan Plateau dropped by 4C with a devastating effect on agriculture – something with serious implications for today
The collapse of a Tibetan kingdom in the 17th century may have been caused by falling temperatures, researchers have said.
The Guge kingdom was founded in western Tibet at the end of the 10th century and flourished for about 700 years before collapsing in the 1630s.
Its defeat by the neighbouring Ladakh kingdom ended its existence as an independent state, but then the population and society collapsed in the region.
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Previous studies have looked at changes in crop yields and droughts in the region, but previously no evidence about changing temperatures was available.
But the latest study has found evidence that the local temperature fell by about 4 degrees Celsius between the 14th and 17th centuries, contributing to diminished crop production and the kingdom’s downfall.
The world experienced a period of cooling in this time, which is sometimes referred to as a mini ice age, and the impact of climate change has previously been linked to a series of conflicts and disasters around the globe, from the Thirty Years’ War in Germany to the collapse of the Ming dynasty (1368-1644) in China.
Researchers from China, the United States and the Netherlands collected and analysed sediment samples from lakes in Tibet to understand the historical temperature change in the study, which was published in the journal Paleoceanography and Paleoclimatology last month.
The researchers analysed 29 surface sediment samples from lakes on the Tibetan Plateau and 39 additional samples from a previously published data set on Chinese lakes.
They were able to track temperature changes by looking at sediments in the lakes, including a certain type of lipid, an organic compound produced by bacteria known as brGDGTs, which is highly sensitive to temperature changes.
By tracking the changes in lipid levels in a 2,000-year sediment core from Xiada Co lake, which is near the ruins of the Guge kingdom, they were able to determine how the temperature had changed over that period.
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“We found that it was warm during the heyday of the kingdom, but temperatures dropped from 2 degrees Celsius to –2 degrees Celsius at the end of Guge,” said Liang Jie, lead author of the study and a postdoctoral research associate at the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences (ITPCAS).
“Don’t underestimate the change from the declining temperature. It will lead to the reduction of crop production in Guge due to low temperatures and reduced glacier meltwater for agricultural irrigation.”
Xie Haichao, co-author of the study and an assistant researcher at ITPCAS, said that before this study, there was little research on the quantitative temperature and crop pattern reconstruction in this region.
“We want to study how climate changes influence Guge agriculture and farming,” he said.
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“This [warming] is a robust prediction of climate models, yet there is considerable uncertainty about the amplitude of warming in the future,” he said.
“We have very few records from high mountains that quantify temperature changes in the past, with which we can test the accuracy of climate model hindcasts. Records such as this one are therefore important to testing climate model performance.”
The Tibetan Plateau has the most glaciers outside the Arctic and Antarctica, and is referred to as the “third pole” and the “water tower of Asia”.
Over the last century, temperatures on the plateau have increased by up to 0.3 degrees Celsius per decade, which is three times faster than the global average.
The increasing temperatures have resulted in 82 per cent of the plateau’s glaciers retreating during the last half-century.
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“This study is not only to improve our understanding of the Guge kingdom, but also advance our knowledge of how climate change will impact our lives in future,” Xie said.
China started its second scientific research survey on the Tibetan Plateau in 2017, focusing on the plateau’s glaciers, climate change, biodiversity and ecological changes.
