Indian monsoons are likely to become stronger and more erratic if global warming continues unchecked, threatening farming and incomes across the region, researchers said on Wednesday.
Monsoon rains will likely increase by about 5% for every degree Celsius of warming, found the study of more than 30 state-of-the-art climate models from around the world, published in the journal Earth System Dynamics.
"What is really on the line is the socio-economic well-being of the Indian subcontinent," said co-author Anders Levermann, a climate scientist at Germany's Potsdam Institute for Climate Impact Research and New York's Columbia University.
"A more chaotic monsoon season poses a threat to the agriculture and economy in the region and should be a wake-up call for policy makers to drastically cut greenhouse gas emissions worldwide."
Governments are lagging behind in implementing the 2015 Paris Agreement, which aims to hold the rise in average global temperatures to "well below" 2 degrees Celsius above preindustrial levels, and preferably 1.5C.
Temperatures have already risen by more than 1C since pre-industrial times, and scientists warn further increases risk triggering tipping points that could render swathes of the globe uninhabitable, devastate farming and drown coastal cities.
About 80% of the annual rainfall over India occurs between June and September, with an average of 88 centimetres of rain over the four-month period determining yields for crops, such as rice, wheat and sugarcane, and replenishing dams.
Too much rainfall can harm plants, including rice, on which the majority of India's population depends, as well as causing flooding and soil erosion.
Monsoon rains are critical for farm output and economic growth as about 55% of India's arable land is rain-fed and the sector employs more than half of its 1.3 billion population, boosting rural spending.
India's monsoon rains are expected to be 103% of the long-term average in 2021, according to the private forecasting agency Skymet, following two consecutive years of above average rains in 2020 and 2019, for the first time in six decades.