Delhi over the last weekend received heavy rainfall, with a similar spell of rains happening two weeks before that. The heavy rains were recorded as high as 87.2 mm at Lodhi Road on October 8 and 9. Delhi has received 121.7 mm of rain in the first 10 days of October, almost three times more than it did in August, with the city receiving 41.6 mm of rainfall.
The rain was unusual for the region for the time of the year with the northwestern parts of India, including the national capital, receiving 396% of surplus rains in the first ten days of October.
By the first week of October, India had received surplus rain of 6% across the country.
In 2021, September saw the second-highest rainfall that has been recorded between 1994-2021, the highest being in 2019. In 2021 southwest monsoons were normal, the period of rainfall has been erratic.
BOOM spoke to climate experts on the changing rainfall seasons and their connection with climate change.
Are rainfall patterns changing?
While a study conducted at Brown University that south Asia's monsoon will be affected by the increase in greenhouse gases like CO2. A report by the Intergovernmental Panel on Climate Change had said that while events like heavy rains are expected to happen once in 20 years, the phenomenon may become as frequent as once every five years by the end of this century. "About 86 million people are likely to get exposed to floods by 2030, about two-and-a-half times more than in 1970s," a report in the Centre for Science and Environment said.
Delhi witnessed untimely rain twice in the last month after multiple "weather systems" were seen active over northwest India at the same time like the western disturbances and low-pressure area. These weather systems are usually active during the peak monsoon which is from June to September.
BOOM spoke to environmentalist Himanshu Thakkar who said that while climate science was not advanced to confirm if a certain event is linked to climate change, it is known scientifically that climate change will bring about changes in rainfall, winds and heatwave patterns. "Science has been telling us this kind o change is likely to happen, this has been happening. Such events are not new and they will happen more," Thakkar said.
He emphasised the need to have effective policies to minimise the losses caused by heavy rains. "We need to make our system resilient and the best way is to protect the natural infrastructure," he said.
He said that disasters like avalanches, high floods and landslides are all happening because of climate change. "But we need to adapt to climate change," he said.
According to a report by the World Bank, South Asia is expected to see hotter summers, longer monsoons and increased droughts as global temperatures increase. "The region's extreme vulnerability has long been apparent. More than half of all South Asians, or 750 million people in eight countries have been affected by one or more climate-related disasters in the last two decades," the report says.
Thakkar said that to accommodate for the changing weather patterns, our definition of the monsoon duration also needs to change. "Central Water Commission needs to do flood forecasting beyond monsoon also," he added.
Climate scientists Professor Raghu Murtugudde explained that the late monsoon in India was because of a combination of La Nina coupled with local conditions.
What is La Nina?
Under normal conditions, winds on the Pacific ocean move towards the west along the equator to take warm water from South America to Asia. For India, La Nina means good rainfall during the monsoon season. "La Nina sets up a pattern of pressure. From the Bay of Bengal side, we have winds going into the pressure and they are forced to go up north. So we had heavy rains from Delhi to UP and Bihar. On the west, we had very heavy rain in Mumbai recently."
India is in the third year of La Nina which is why India had 7% more rainfall this monsoon season as compared to the normal.
With sea surface temperatures increasing, episodes of La Ninas will also increase, he said. "Next year it is unlikely to be La Nina and it will be very unusual if that happens," he said. El Nino and La Nina are cyclical in patterns. El Nino warms the sea surface temperature in certain parts of the pacific ocean stopping southeast trade winds from flowing over India and reducing rainfall.
"What will happen is that in the next 10 years instead of getting three La Ninas we will get six," Murtugudde said.
Can we minimise losses caused by changing weather?
Murtugudde said the trend of changing rainfall patterns will persist, while the experts need to monitor the situation for 10 to 15 years to see if the patterns have shifted permanently and if there is a need for new definitions. "While we do that we need to improve our forecast systems to reduce crop damage," he said, adding that excess rain can be stored and utilised to make up for the rainfall deficit.
Similarly, Thakkar suggested the usage of techniques that help farmers increase the soil's water retention capacity like the use of organic fertilisers. "Once the monsoon is over, Indian farmers depend on groundwater for irrigation and the water table which is also depleting due to overuse," Thakkar said.
"The excess rain in late monsoons can be stored and utilised to replenish the depleting groundwater," he added.
