Mawmluh cave
© Ashish SinhaStalagmites in the Mawmluh cave, near the town of Cherrapunji in the state of Meghalaya — one of the wettest locations in the world.
A new study published in the Proceedings of the National Academy of Sciences reveals that catastrophic droughts — unlike anything observed in the last 150 years — have been a regular occurrence within the Indian subcontinent throughout the last 1,000 years. The troubling new data indicates that the region's current rainfall predictability could give way to decades-long drought, posing an enormous potential threat to human life if no mitigating measures are taken.

California State University, Dominguez Hills Professor of Earth Science Ashish Sinha was a lead author on the study, working alongside an international team of researchers to develop the new record. The team analyzed oxygen isotopes in stalagmites from the Mawmluh cave, near the town of Cherrapunji in the state of Meghalaya — one of the wettest locations in the world. The stalagmites work similarly to tree rings, recording the region's rainfall history within their geochemistry.

Analysis of the stalagmites revealed links between multi-year droughts and significant geopolitical changes in India, including records of crop failure, mass death, and societal collapse over the past millennium — particularly in the 16th and 18th centuries.

Comment: The similarities with our own time are ominous.

"Our study shows that protracted droughts, lasting at least 3 years or longer, tend to occur in clusters within decades-long intervals of weaker monsoon rainfall that are separated by centuries-long periods of relatively stable climatic conditions — much like the conditions during the last 150 years where such protracted droughts are essentially absent," said Sinha.

The research team warned that the lack of protracted droughts over the last 150 years may be leading to a false sense of security and ill-informed water resource infrastructure policies in India — soon to be the most populous country on earth.

Gayatri Kathayat, a lead author of the study and associate professor at Xi'an Jiaotong University in China, said:

"If such protracted droughts were to reoccur in the future, they can easily overwhelm the adaptive capabilities of modern societies unless a longer-term and holistic understanding of monsoon variability is incorporated into the region's drought management and mitigation planning."