New Timing for Stubble Burning in India

Every year for decades, long rivers of smoke and mist spread across the Indo-Gangetic plain in northern India from October to December. This is when farmers in Punjab, Haryana, Uttar Pradesh, Madhya Pradesh and other states burn the ‘stubble’ of plants after harvesting rice.

When winds are weak and the atmosphere is stagnant, haze can push air pollution levels several times above the limits recommended by the World Health Organization. Smoke typically mixes with particles and gases from other sources, such as industry, vehicles, house fires (heating and cooking), fireworks and dust storms, to form the haze, although scientists consider stubble burning to be a major factor.

In some ways, the seasonal timing of stubble burning in 2025 followed typical patterns. Air quality deteriorated in Delhi and several other cities for about a month after crop fires intensified in the last week of October, said Hiren Jethva, a Morgan State University atmospheric scientist based at NASA’s Goddard Space Flight Center. For about a decade, Jethva has been tracking India’s stubble fire season using satellites and making predictions about the intensity of the next fire season based on vegetation observations.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this image of a smoky haze darkening the sky over much of the plain on November 11, 2025. According to reports, it was the first of several days in 2025 when pollution levels exceeded 400 on India’s Air Quality Index, the highest rating on the scale. As in previous years, poor air quality has prompted authorities in some regions to close schools and introduce stricter air quality controls in buildings.

However, the daily fire schedule deviates from what Jethva has seen in the past. He began tracking the number of fires years ago by counting observations primarily from MODIS, which flies over sites on Earth every morning and afternoon on the Terra and Aqua satellites, respectively. Then, most of the fires were started in the early afternoon between 1 p.m. and 2 p.m. local time.

But in recent years, stubble fires have occurred gradually later in the day, Jethva said. He identified this change by analyzing observations from GEO-KOMPSAT-2A, a South Korean geostationary satellite launched in late 2018 that collects data every 10 minutes.

Most stubble fires now occur between 4 p.m. and 6 p.m., he explained, meaning that fire monitoring systems that rely solely on MODIS, or similar sensors like VIIRS (Visible Infrared Imaging Radiometer Suite), miss many fires. “Farmers have changed their behavior,” he said.

Its analysis of GEO-KOMPSAT-2A observations indicates that stubble burning activity in Punjab and Haryana was moderate in 2025 compared to other recent years. This year, the number of fires was higher than in 2024, 2020 and 2019, but fewer fires than in 2023, 2022 and 2021, he found.

Researchers from the Indian Space Research Organization also highlighted the change in the stubble burning schedule. In a Current science In a study published in 2025, a group reported that MSG (Meteosat Second Generation) satellite observations showed a shift in peak fire activity from around 1:30 p.m. in 2020 to around 5:00 p.m. in 2024. In December 2025, researchers from the International Forum for Environment, Sustainability and Technology (iForest) published a multi-satellite analysis that came to a similar conclusion.

Meanwhile, determining precisely how much stubble fires contribute to Delhi’s poor air quality compared to other sources of pollution remains a subject of active study and debate among scientists. “Studies report contributions ranging from 10 to 50 percent,” said Pawan Gupta, a NASA research scientist specializing in air quality.

Gupta estimates that the contribution to stubble burning varies from 40 to 70 percent on a given day, falling to 20 to 30 percent if averaged over a month or burning season, and less than 10 percent if averaged annually. “Weather conditions, such as low boundary layer height and low temperatures, during the burning season add additional complexity,” he said.

The timing of fires can influence the extent to which stubble burning affects air quality. Some modeling research suggests that evening fires may lead to a greater accumulation of particle pollution overnight than early afternoon fires because the planetary boundary layer, the lowest part of the atmosphere, tends to be shallower and have weaker winds at night, allowing pollutants to build up.

NASA Earth Observatory image by Michala Garrison, using NASA MODIS data EOSDIS LANCE and GIBS/Worldview. Story by Adam Voiland.

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