Chinese cave 'graffiti' tells story of climate change

Researchers have discovered unique 'graffiti' on the walls of a cave in central China, which describe the impact of seven drought events between 1520 and 1920.
The inscriptions were found on the walls of Dayu Cave in the Qinling Mountains of central China.
The information contained in the inscriptions, combined with detailed chemical analysis of stalagmites in the cave, together paint a picture of how societies are affected by droughts over time.
The results also point to potentially greatly reduced rainfall in the region in the near future.
The climate in the area around the cave is dominated by the summer monsoon, in which about 70 per cent of the year's rain falls during a few months, so when the monsoon is late or early, too short or too long, it has a major impact on the region's ecosystem.

"In addition to the obvious impact of droughts, they have also been linked to the downfall of cultures - when people don't have enough water, hardship is inevitable and conflict arises," said Sebastian Breitenbach of the University of Cambridge, one of the paper's co-authors.

According to the inscriptions in Dayu Cave, residents would come to the cave both to get water and to pray for rain in times of drought.
An inscription from 1891 reads, "On May 24th, 17th year of the Emperor Guangxu period, Qing Dynasty, the local mayor, Huaizong Zhu led more than 200 people into the cave to get water. A fortune-teller named Zhenrong Ran prayed for rain during the ceremony."

Another inscription from 1528 reads, "Drought occurred in the 7th year of the Emperor Jiajing period, Ming Dynasty. Gui Jiang and Sishan Jiang came to Da'an town to acknowledge the Dragon Lake inside in Dayu Cave."
The droughts of the 1890s led to severe starvation and triggered local social instability, which eventually resulted in a fierce conflict between government and civilians in 1900.
The drought in 1528 also led to widespread starvation, and there were reports of cannibalism.
"There are examples of things like human remains, tools and pottery being found in caves, but it's exceptional to find something like these dated inscriptions," said lead author Liangcheng Tan of the Institute of Earth Environment at the Chinese Academy of Sciences.

The researchers used the study results to construct a model of future precipitation in the region, starting in 1982.
Their model correlated with a drought that occurred in the 1990s and suggests another drought in the late 2030s.
The observed droughts also correspond with the El Nino-Southern Oscillation (ENSO) cycle. Due to the likelihood that climate change caused by humans will make ENSO events more severe, the region may be in for more serious droughts in the future, researchers said.
The study was published in the journal Scientific Reports.