Global warming making India’s monsoon season wetter and extreme

A new research reveals that global warming is likely to make the Indian monsoon season wetter and more dangerous. Its making India’s monsoon stronger and more chaotic, with potential severe consequences for food, farming and the economy. The researchers highlighted that from the 1980s, the warming effects of greenhouse gases began to dominate, driving stronger and more volatile rainy seasons.

Researchers at the Potsdam-Institute for Climate Impact Research (PIK) found strong evidence that every degree Celsius of warming would likely increase monsoon rainfall by about 5%. Anja Katzenberger, lead author of the study, said they found that global warming is increasing monsoon rainfall in India even more than previously thought. “It is dominating monsoon dynamics in the 21^st century. This raises the possibility that key crops, including rice, could be swamped during crucial growing stages.”

Rresearch based on computer models has suggested that the global heating caused by greenhouse gases, and the increased moisture in the warmed atmosphere will result in rainier summer monsoon seasons and unpredictable, extreme rainfall events. The latest research, published in Science Advances, adds evidence for the theory by looking back over the past million years to give a sense of monsoons to come.

The monsoon season which generally runs from June to September brings enormous amounts of rain to South Asia that are crucial to the region’s agrarian economy.  The researchers used mud; they drilled core samples in the Bay of Bengal, in the northern Indian Ocean, where the runoff from monsoon seasons drains away from the subcontinent. The core samples were 200 meters long and provided a rich record of monsoon rainfall. Wetter seasons put more fresh water into the Bay, reducing the salinity at the surface.

The scientists through the core samples, analyzed the fossil shells of plankton, measuring oxygen isotopes to determine the salinity of the water they lived in. The high-rainfall and low-salinity times came after periods of higher concentrations of atmospheric carbon dioxide, lower levels of global ice volume and subsequent increases in regional moisture-bearing winds. The new analysis, which compares more than 30 climate models from around the world predicts that more extremely wet rainy seasons, which sweep in from the sea.

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Anders Levermann from PIK and Columbia University pointed out that since Indian society is overall affected by the monsoon in a very strong way, stronger variability produces problems for agriculture, but also for the organization of public life. “If your roads are flooded, if your train tracks are flooded, that inhibits economic productivity. The year-to-year variability would also complicate strategies to cope with the increasing strength of the rainy season,” he said. “More chaos in the Indian monsoon rainfall will make it harder to adapt.”