Reduced farm fire claims misleading, farmers evading satellites: ISRO study

Farmers in Punjab and Haryana shifted stubble burning timings from early afternoon to evening hours, likely to avoid detection by polar satellites, thereby leading to a significant underestimation of farm fire counts and associated emissions as monitoring relies solely on polar-orbiting sensors, claimed a study by the Ahmedabad-based Space Applications Centre (SAC) of the Indian Space Research Organisation (ISRO).

ISRO scientists, in the study, ‘Evidence of shift in stubble burning timing over North-West India from geostationary satellite observation’, have claimed that they have utilised geostationary satellites as they can capture fire activity more effectively due to their effective temporal coverage.

Geostationary satellites orbit the Earth at a high altitude of around 36,000 km, while polar satellites orbit at a much lower altitude of 600-800 km.

The scientists have analysed geostationary Meteosat Second Generation (MSG) meteorological satellites equipped with the Spinning Enhanced Visible and Infrared Imager (SEVIRI) fire detections over Punjab and Haryana (acquired every 15 min) for the period between October 15 to November 30 during 2020–2024.

“In 2020, fires typically ignited around noon, peaked near 13.30 IST, and subsided by 15.30 IST. We observe a gradual temporal shift between 2021 and 2024, with peak fire activity occurring around 17.00 IST in 2024. At the same time, the diurnal window of fire activity narrowed substantially, suggesting an informed adjustment by farmers to avoid detection by polar-orbiting sensors,” the study said.

In his independent findings, Hiren Jethva, a senior aerosol remote sensing scientist with NASA Goddard Space Flight Center, said, “Historical satellite record for 2002–2021 suggests around 15,000 fire counts (via Moderate Resolution Imaging Spectroradiometer-a NASA satellite). Predictions missed the mark in 2022–2024 due to shift in peak fires to late afternoon, dodging satellite eyes.”

“Claims of 92 per cent reduction in Punjab’s crop fires are false/misleading. The data relied on NASA–NOAA satellites that miss most late-afternoon fires,” he said.

The findings of the present study highlight a critical gap in current fire monitoring practices. Underestimation of active fire events during October–November in Punjab and Haryana can lead to a substantial underestimation of carbon emissions, the study said.

Traditionally, farmers in the region burned crop residues twice a year -- once between October–November prior to planting wheat, and again in April–May before sowing paddy. The large-scale burning events release substantial amounts of smoke, particulate matter and aerosols, leading to severe degradation of air quality across the Indo-Gangetic plains, with Delhi being a prominent example of this crisis.

The findings by ISRO contradict the government’s official statement this week that farm fires in Punjab and Haryana had dropped nearly 90 per cent due to “state action plans, deployment of crop-residue management machinery and strict enforcement measures”.

Future efforts should prioritise the combined use of fire data from both LEO and geostationary satellites, treating them as complementary rather than stand-alone sources, suggest researchers.