Climate Change Tracker: India's Uneven Monsoon Rainfall
Due to global warming, the trend of extreme monsoons with long dry spells alternating with very heavy rains is here to stay
June-September are the monsoon months according to the India Meteorological Department (IMD). With more than half the season over, India is looking again at uneven rains. According to data released by IMD earlier this month, June was an unnaturally wet month, with all-India rainfall being 17.6% above normal. In July, things went the other way, with a rain shortfall of 10% across the country. This meant it was the driest July on record. At the same time, however, IMD forecast that the months of August and September would see excess rains through the country, with September, in particular, forecast to see very heavy rainfall.
Since the forecast, there has been intensely heavy rain across western and peninsular India. On 5 August, Mumbai recorded 216mm of rain in just 12 hours. Some parts of the city, like Malabar Hill, recorded as much as 309mm of rain in the same period. According to the Colaba weather observatory in south Mumbai, this was the highest single-day rainfall in 22 years for the month of August.
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At the same time, the Nilgiris in Tamil Nadu recorded 820mm rain in 24 hours, triggering massive landslides and flooding. In the past week, regions up and down the west coast have recorded rainfall ranging from 390-710mm. In Kerala’s Idukki district, a massive landslide on 7 August killed at least 15 people, mostly tea garden workers. The state, which was rain-deficient till end-July, made up for that deficit within the first 10 days of August.
In Delhi, monsoon rainfall in August has so far been 72% less than normal. This, according to IMD data, is the lowest August rainfall in 10 years. According to the Safdarjang observatory, Delhi has recorded just 31.1mm rainfall so far this month. The normal is 109.6mm. However, in July, there were excess rains in the Capital, 12% over normal.
During last week’s downpour, climate scientist Roxy Mathew Koll of the Indian Institute of Tropical Meteorology (IITM), Pune, said in a statement, “In our analysis of rainfall data over the last 70 years, we find a three-fold rise in extreme rains along the west coast and central India. This is because the monsoon winds over the Arabian Sea are now exhibiting large fluctuations due to a warmer environment."
This uneven distribution of rainfall is one of the reasons for floods and landslides, apart from the damage to agriculture. According to the recent Ministry of Earth Sciences (MoES) report, Assessment Of Climate Change Over The Indian Region, monsoon precipitation over north India has decreased by 6% (1951-2015) due to the polluting aerosol “brown cloud".
The report says that in the coming decades, the monsoon is expected to become more extreme. There will be longer dry spells, alternating with very heavy rain. "Neither very heavy rainfall, nor an increasing duration of dry spells is either good for agriculture or for groundwater restoration," said climate scientist Chirag Dhara, one of the authors of the assessment, on the Mint Climate Change Tracker podcast recently. Going by annual trends over the last few years, it would seem that wildly fluctuating monsoon rainfall, as a result of global warming, is here to stay.
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FIRST PUBLISHED13.08.2020 | 09:00 AM IST