India set to lower ‘normal rain’ baseline as droughts bite

India’s meteorology agency is set to lower its baseline of what constitutes a “normal” monsoon, as it grapples with a multi-decade rain deficit and the challenges of making forecasts in an era of worsening climate change. 

“India is in the middle of a multi-decadal epoch of low rainfall,” Sivananda Pai, head of climate research and services at the India Meteorological Department told the Financial Times. 

As a result of years of disappointing rains, Dr Pai said the agency was preparing to lower its so-called long period average of the amount of rainfall recorded during a normal monsoon by “around 1-2 cm” as part of a once-in-a-decade update to its baseline. The IMD’s current average is 89cm, based on monsoons between 1960 and 2010, while the new one will span the 50 years to 2020. 

But underlying that apparently modest downgrade in total normal rainfall across the monsoon season, the IMD expects “regional variation in rainfall to increase substantially”, driven in part by the worsening impact of climate change on the Indian subcontinent. 

“We will see many more heavy rainfall events . . . while other places will undergo prolonged dry spells, even if the total stays roughly the same,” said Dr Pai, highlighting the record rains in Mumbai last month even as Chennai in the south experienced its worst drought in decades. 

While scientists remain divided on whether warming and air pollutants will weaken or strengthen the Indian monsoon overall over the next century, they agree that extreme events are set to spike. That view is summed up by the Intergovernmental Panel on Climate Change, which said in a 2018 report that “all models project an increase in heavy precipitation events” in India and other countries in south Asia. 

Despite being one of the only major economies on track to meet its commitments under the 2015 Paris accords, according to Climate Action Tracker, India is already on the front lines of the global climate crisis. 

Large parts of India have suffered a record heatwave this year as soaring temperatures become the new normal, while coastal communities in particular have been hit hard in recent months by severe flooding, increasingly powerful cyclones and rising sea levels. 

India’s agriculture sector, which employs nearly half of its workforce, remains heavily dependent on fickle monsoon rains — with droughts and floods triggering mass farmer suicides and protests. Sunita Narain, a prominent environmental activist, has called the monsoon the “real finance minister of India” for the powerful role it plays in the country’s rural economy. 

But despite investments since 2010 in more accurate forecasting tools to allow citizens to mitigate damage, Dr Pai cautioned that India’s ability to predict weather and climate patterns remains imperfect — and that climate change is only heightening the challenge. 

“We are lucky to have a long history of observation records and good network of monitoring stations, but we need far better modelling tools,” he said, adding that a lack of data from regional neighbours racked by political instability as well as the need for more computing power are holding back the IMD. 

Still, Dr Pai sees some hope that investments, including in new supercomputers at the agency’s site in Pune, might be paying off. “IMD had never predicted a monsoon correctly before 2015, but we have now made several years of good predictions,” he said, adding that machine learning algorithms are expected to be deployed within the next two years. 

“Once people have faith in forecasts they begin using them, preparing for changing patterns . . . modifying their crop choices, pricing insurance correctly and so on.”

Additional reporting by Leslie Hook in London