50 firecrackers per wedding: DSS’s ‘science’ behind stubble fire rethink

On November 16, the Decision Support System (DSS) run by the Indian Institute of Tropical Meteorology (IITM) calculated that the contribution of stubble burning to Delhi’s PM2.5 (particulate matter with diameter below 2.5 microns) was 37.5% on November 15.
On November 18, it revised its calculation to 21.56%.
Similar revisions were made for November 14 — from 33.33% to 24.51% — and November 13, from 30.8% to 14.82%.
The reason: so-called false fires recorded by satellites due to fog, and the large number of weddings in Delhi (based on news reports).
Researchers running DSS assumed that 50 firecrackers were burst at each wedding held in Delhi.
“The fire count was adjusted and run again, as we saw newspaper and media reports that a number of weddings were held in the period,” IITM scientist Sachin Ghude told HT. Gude did not disclose the source of the data shared in these reports.
“We know this is a crude correction and not a very accurate correction,” he admitted.
And that absence of science, logic, and exactitude is the beginning of the reason why the various administrations in charge of various aspects of the national capital, have been unable to address the annual problem of pollution.
On Monday, the AQI peaked at 494 at 4pm; on Tuesday, it was only marginally better at 460.
DSS was launched in 2021 to identify the estimated contribution of sources of pollution within Delhi and outside it. It calculates the estimated contribution of eight sources within Delhi and from 19 NCR (national capital region) districts, in addition to stubble burning. DSS comes under the Union ministry of earth sciences and is run by a team of eight scientists at IITM. It is the only model sharing data on sources contributing to Delhi’s bad air.
The DSS website on Tuesday evening stated: “The estimates of the contribution from stubble burning for 13th, 14th and 15th November 2024 are revised by taking into account the emissions from bursting of firecrackers in Delhi (as a part of the wedding celebrations), which were not taken into consideration earlier.”
Ghude said that calculation of stubble burning to PM2.5 is dynamic, thus allowing them to change inputs, if required.
“We use the VIIRS satellite imagery and the model accounts for a wide radius, including Punjab, Haryana, Madhya Pradesh and Uttar Pradesh too. It also accounts for meteorological conditions. We have now accounted for marriages occurring based on the numbers seen online and thus, recalculated the fire count.”
On November 12, the Confederation of All India Traders’ (CAIT) secretary general and Chandni Chowk MP Praveen Khandelwal said in a statement that around 50,000 weddings were held in the Capital that day, on the occasion of Dev Uthani Ekadashi.
“This marks the beginnings of the wedding season, which will continue until December 16. This season’s first phase will span 18 days, with approximately 4.8 million weddings expected across the country, including around 450,000 in Delhi alone,” the statement added.
It is likely the weddings were factored into the calculations for subsequent days — for the DSS reading of stubble burning’s contribution to AQI on November 16 was 25.10%,and on November 17, 13.06%.
IITM’s public relations officer did not respond to an e-mail seeking a comment.
Professor SN Tripathi from IIT Kanpur, who is also part of the Steering Committee of the National Clean Air Programme (NCAP), said the way farm fire contribution is calculated and its methodology may require reassessment. “This does not seem very scientific, in the sense that drawing a correlation between weddings, firecrackers and stubble residue burning seems difficult. We know the chemical composition of stubble burning and firecrackers is also different, so we should differentiate between the two sources,” he said, calling for greater transparency.