Key Delhi air monitor went dark in peak farm fire week

NEW new new delhi : The regime posture that tracks pollution sources in Delhi went restrained for four days during the first week of November — historically, some of the period when smoke from agricultural burning contributes most heavily to the capital’s toxic air — and was updated only after HT asked authorities about the missing data.The Decision Support System (DSS), which estimates how much different sources contribute to Delhi’s PM 2.5 levels, last provided data on Friday. When the system finally updated late on Tuesday evening, it revealed no stubble burning contribution data for November 1 and 2.Past data shows stubble burning’s contribution to Delhi’s air has historically surged above 35% during the first week of November, reaching as high as 48% on a single day in 2021. This year’s readings show just 4.06% on Monday and 1.74% on Tuesday.Last year on November 1, farm fires accounted for 35.1% of Delhi’s PM 2.5 pollution. The contribution remained at 35% till November 3 in both 2023 and 2022, according to DSS records.The Indian Institute of Tropical Meteorology in Pune, which operates the model, and the Commission for Air Quality Management did not respond to queries on Tuesday about the data gap.Harvesting and farm fires are likely delayed this year following widespread floods in Punjab, but burning has been rising in recent days. Punjab recorded 256 fires on Sunday while Haryana logged a season-high 23 fires the same day.To be sure, the region appears to have mostly been spared of an air pollution crisis also due to more active weather conditions that usual.“We have seen wind speeds remain high so far — the speed is enough for dispersion. At the same time, Diwali was earlier than usual this year and farm fires are low, so we are not seeing the kind of emissions we usually see in early November,” said Dipankar Saha, former head of CPCB’s air laboratory. But he warned that if wind speeds drop again, it will eventually lead to accumulation of pollutants over time.The DSS typically provides daily source contribution estimates along with a two-day forecast. It calculates pollution contributions from Delhi’s own emissions and 19 neighbouring NCR towns, with stubble burning percentages updated later based on actual fire counts.The system showed Delhi’s transport sector contributed 19.91% to Tuesday’s PM 2.5 levels, followed by emissions from Jhajjar at 6.54% and Gautam Buddha Nagar at 6.15%.The DSS blackout is part of a broader pattern of monitoring failures this year. On Diwali night, nine of Delhi’s 39 air quality monitoring stations stopped recording data entirely during critical hours between 11 p.m. And 4 a.m. — the second-highest number of such failures since 2021.“Transparency is important when we talk about fighting pollution,” said Sunil Dahiya, founder and lead analyst at environmental think tank Envirocatalysts.Dahiya, however, pointed to other problems with the DSS. “With an outdated emissions inventory, it seems none of the agencies and bodies which should be using this data are utilising it, which explains the semi-frequent updates in between.”The model continues to run on an outdated 2021 emissions inventory, officials have acknowledged, raising doubts about forecast accuracy. The system was operationalised on October 5 ahead of the winter pollution season — the same inventory issue that prompted CAQM to halt it last year and request improvements from IITM.During last winter, DSS data was available from the start of October till November 29 before going dark until December 9. CAQM said at the time it would not use the system for pollution-related decisions because the emissions inventory was too old, though the model would continue sharing information.At least three major real-time source identification studies have been halted or rendered obsolete in the past four years. In 2021, the Delhi government stopped a study by Washington University before its data was made public, citing “unsatisfactory” results. The work was reassigned to IIT Kanpur the same year, but that two-year study ended in November 2023 with the government again dissatisfied with methodologies and results. No replacement system has been established.“It is a model which ticks a lot of boxes, but eventually, is turning out to be a waste of funds, unless our data is running on a new emissions inventory and is updated regularly,” Dahiya said.