Chinese scientists have found signs of a super rainstorm etched in the shells of snails, in an experiment that could help unlock evidence in the fossil record of ancient “tipping points” in the Earth’s environment.
The scientists, led by climate change researchers from the Institute of Earth Environment, Chinese Academy of Sciences, in Xian, conducted the experiment on the shells of four living specimens – two collected in the Zhengzhou area before a devastating rainstorm hit the city in July 2021, and two after the storm had passed.
The storm caused catastrophic losses to life and property in Zhengzhou, at one point dumping a year’s worth of rain on the city in a few days.
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The downpours were described as a “once-in-a-millennium” event but that definition was based on data of the past hundred years.
“With the acceleration of global warming, the climate background of extreme weather events is undergoing rapid changes,” the researchers said in a paper published in Science Bulletin last week.
“Whether the ... Zhengzhou super rainstorm is a ‘once-in-a-millennium’ disaster or a new more regular event in a warmer world is a pressing question requiring clarification.”
The researchers cut up the shells and examined the ratio of two stable oxygen isotopes, oxygen-18 and oxygen-16, compiling a daily record.
The ratio is commonly used in paleoclimate research to gauge past climate change conditions, and the team found a dramatic negative shift that they attributed to the Zhengzhou rainstorm.
By comparing the theoretical calculations of water isotopic changes during the rainstorm with snail shell measurements, the scientists found that snail shells could be a record of large-scale precipitation events.
“This special microstructure associated with the ... shell variation might have the potential to be a sufficient physical marker for identifying extreme rainstorms,” the team said.
Gathering this kind of information from fossils could offer data well beyond a hundred years and enable scientists to investigate the relationship between the frequency of extreme rainstorms and different climate backgrounds.
China has been under great pressure to minimise the damage of global warming-induced extreme weather. The country has been further hit by floods and scorching weather this year.
The researchers said in their paper that the limits of modern weather data and climate models made it challenging to understand the “tipping points” triggering shifts to entirely different conditions.
Paleoclimate archives show the Earth’s climate change framework over millions of years, but they are limited in their ability to trace past weather variations, according to the paper.
Looking at specimens such as mollusc shells could fill that gap.
The paper said the work could be extended to a large number of fossil snail shells preserved in the Loess Plateau in north-central China that might reconstruct a relationship of extreme rainstorms under different climate backgrounds, such as the glacial period.
The researchers said extreme precipitation events could “offer a historical reference for future projections of extreme weather events in a warming world [and could] serve as a tool for evaluating the accuracy of climate models’ simulations of extreme weather event responses to external forcing changes”.
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