Delayed monsoon exit may mean ‘severe’ smog: Report
- The findings are in line with remarks by other experts, who said they fear a last-minute spike could push Delhi’s air into severely polluted category, as reported by HT on Thursday.
Intense and heavy monsoon spells this season have helped Delhi breathe relatively cleaner air this October compared to previous years, an air quality analysis by the Centre for Science and Environment (CSE) has shown. However, the analysis also warns that the late withdrawal of monsoon in north India could also lead to “severe peak in smog” during winter as farmers rush to burn crop remnants in the shorter window they will now have to clear their fields.
The findings are in line with remarks by other experts, who said they fear a last-minute spike could push Delhi’s air into severely polluted category, as reported by HT on Thursday.
Anumita Roychowdhury, executive director (research and advocacy), CSE, said the pre-winter air this year has been relatively cleaner, primarily because of the impact of intense and prolonged monsoon. “The objective was also to understand the starting line of the onset of the winter pollution season or pre-winter levels in this region, and also to understand the longer-term trends in seasonal variations,” she said.
“While winter pollution cannot be predicted at this moment, the evidence of rising summer pollution in 2021 despite the lockdown and the evidence of a synchronised effect of winter pollution across the Indo-Gangetic Plain add to our concern. How soon and intensely the winter pollution will hit us will depend on the scale and speed of action across the region and leveraging it for more sustained air quality gains.”
The analysis warned that while the prolonged and intense monsoon might have temporarily averted the city’s annual air emergency, this could also cause more intense smog episodes.
“This winter we may get a much severe peak in smog, as farm stubble fire counts may get more concentrated due to the delayed effect of the rains. To counter this, action must be scaled up right away,” said Avikal Somvanshi, programme manager at the urban data analytic lab, CSE.
The report said that normally, the first phase of winter smog is triggered by large-scale stubble burning in the agrarian states of Punjab, Haryana, and Uttar Pradesh. It said that the peak contribution of stubble smoke this year was registered on October 16 when 14% of Delhi’s PM2.5 was attributed to stubble fire smoke.
“Heavy rains in the following days washed out the first build-up of the season. The smoke season generally peaks around the cusp of October and November, with contribution spiking to over 40% on the worst days,” said Somvanshi.
In 2020, during the stubble burning season October 1-November 29, an average 12.2% per day of Delhi’s PM2.5 pollution came from farm stubble fire smoke. This was considerably higher than in previous years – in 2019, contributions stood at 8.9% per day, while it was 10.9% per day in 2018. The findings of the report showed that the city-wide PM 2.5 average for the monsoon this year stood at 41ug/m3, with 96 days meeting the 24-hour standard. There was a progressive increase in the number of cleaner days with an average 6% annual improvement since 2018.
“In Delhi, Dr Karni Singh Shooting Range recorded the lowest seasonal average of 33ug/m3, while the National Stadium had 100 days that met the daily standard. Anand Vihar, with a seasonal average of 61ug/m3 had 54 days meeting the standard and was the worst hotspot in the city,” the report read.
It added. “The start of the monsoon’s retreat date almost perfectly coincides with the start of bad air days in Delhi—when the daily PM2.5 average breaches the standard and mostly remains above for rest of the season.”