Why Are Farmers Changing Their Stubble Burning Time? NASA Data Reveals a New Strategy To Avoid Satellites
NASA and ISRO have reported that North Indian farmers are shifting stubble burning to late evenings (4-6 PM) to evade satellite detection. This change traps pollutants in a shallow atmospheric layer, worsening overnight smog. Despite official claims of a 90% drop in fires, "Severe" 400+ AQI levels persist across the Indo-Gangetic Plain.
New Delhi, December 17: As the 2025 winter haze settles over the Indo-Gangetic Plain, new satellite analysis reveals a significant shift in farmer behavior that is complicating air quality monitoring. NASA scientists and international researchers report that farmers in northern India have begun burning crop residue significantly later in the day, effectively bypassing the primary satellite sensors used to track seasonal pollution.
For years, the peak time for stubble burning in states like Punjab and Haryana was between 1 pm and 2 pm. However, Hiren Jethva, a NASA-based atmospheric scientist, has identified a trend where most fires are now lit between 4 pm and 6 pm. This shift means that the MODIS and VIIRS sensors - high-resolution instruments that pass over the region in the morning and early afternoon- are missing a substantial portion of the activity.
Data from geostationary satellites, which monitor the area every ten minutes, confirmed that peak fire activity has migrated from the afternoon to the late evening over the last five years. Stubble Burning Fine Increased: Centre Doubles Fines to Combat Pollution, Farmers Burning Stubble to Pay Up to INR 30,000 Penalty.
2025 Pollution Levels and Trends
The 2025 season saw air quality in Delhi and surrounding regions deteriorate sharply in late October. On November 11, 2025, pollution levels crossed the 400-mark on India’s Air Quality Index (AQI), the "Severe" category. This prompted local officials to implement emergency measures, including school closures and restrictions on construction.
Analysis of the 2025 season indicates that while fire activity was "moderate" compared to the last decade, it was higher than in 2024. Specifically:
- Higher activity: More fires were recorded than in 2024, 2020, and 2019.
- Lower activity: Fewer fires occurred compared to the peak burning years of 2021 through 2023.
Impact of Evening Fires on Air Quality
The timing of these fires may actually be worsening the air quality impact. Pawan Gupta, a NASA research scientist, noted that evening fires occur when the "planetary boundary layer" - the lowest part of the atmosphere - becomes shallower and winds weaken.
Because the atmosphere is more stagnant at night, pollutants from evening fires are trapped closer to the ground, leading to a more intense overnight buildup of particulate matter compared to fires lit during the warmer, windier afternoon hours. Thick Fog Blankets Several Cities in Punjab, Overall Air Quality Remains Moderate.
Determining the Source of Smog
The exact contribution of stubble burning to Delhi's pollution remains a subject of scientific debate. According to Gupta, the contribution varies depending on the timeframe:
- Daily Peaks: During heavy burning, stubble smoke can account for 40% to 70% of local pollution.
- Monthly Average: Over the entire season, it contributes roughly 20% to 30%.
- Annual Average: Stubble burning accounts for less than 10% of total yearly pollution.
While other sources such as vehicle emissions, industrial output, and dust storms play a role, scientists maintain that the seasonal spike caused by agricultural fires remains the primary driver of the region's winter health crisis.
(The above story first appeared on LatestLY on Dec 17, 2025 01:57 PM IST. For more news and updates on politics, world, sports, entertainment and lifestyle, log on to our website latestly.com).