In the last 9 lakh years, atmospheric carbon dioxide and warming have shaped Indian monsoons

Sediment cores harvested from beneath the seafloor in the Bay of Bengal, off the Indian coast, have uncovered that atmospheric carbon dioxide levels and related warming were “major players” in shaping the intensity of the South Asian monsoon over the past million years, said scientists in a new study.

The findings support numerical models that predict stronger monsoons with increasing carbon dioxide concentrations in the atmosphere in the future.

Along with fluctuations in atmospheric carbon dioxide, the monsoons in the Pleistocene were also sensitive to continental ice volume and moisture import from the southern hemisphere of the Indian Ocean, according to the research that ground-truthed the numerical models used to predict future climate change. The scientists reconstructed the monsoon activity over the past 900,000 years using clues tucked away safely in the sediment resting on the ocean floor.

“This particular paper identified three different mechanisms that are responsible for changing the monsoon over time,” Steven Clemens, a professor of geological sciences (research) at Brown University and lead author of the study, told Mongabay-India. “We demonstrated that monsoon is equally sensitive to the combined effects of ice volume and carbon dioxide as well as how much moisture is flowing out of the southern hemisphere into the northern hemisphere…

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