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NASA : According to satellite data and recent research, seasonal crop fires in northern India are increasingly being started later in the day. Scientists think this change might make it more difficult to track stubble burning and evaluate its effects on air quality, according to NASA.

Farmershave been burning off crop leftovers after the rice harvest for decades, causing vast rivers of smoke and smog to stretch across the Indo-Gangetic Plain from October to December. According to a NASA statement on Monday, the general pattern of the stubble-burning season in 2025 mostly matched predictions, but the daily timing of fires demonstrated a significant divergence from historical patterns.

According to Hiren Jethva, an atmospheric scientist at Morgan State University who works at NASA’s Goddard Space Flight Center, the seasonal timing of stubble fires in 2025 somewhat followed normal trends. He pointed out that as crop fires were more intense in the final week of October, the air quality in Delhi and a few other cities declined for around a month.

Jethva has been utilizing satellite data to monitor stubble burning in India for almost 10 years, and it has used vegetation measurements to forecast the severity of impending fire seasons. The majority of fires were usually started in the early afternoon, between 1 and 2 p.m. local time, in previous years.

But now, that pattern is different. However, Jethva noted that stubble fires had been happening later in the day over the previous several years. According to his study, the majority of stubble fires currently occur between 4 and 6 p.m. “The behavior of farmers has changed,” he said.

Using data from GEO-KOMPSAT-2A, a South Korean geostationary satellite that was deployed in late 2018 and gathers observations every ten minutes, Jethva was able to identify the shift.

According to specialists, satellite photography shows the scope of the issue. NASA’s Aqua satellite’s MODIS sensor recorded a dense smoke and haze plume sweeping over Punjab, Haryana, Uttar Pradesh, and Madhya Pradesh on November 11, 2025.

News sources state that it was the first of numerous days in 2025 when pollution levels above 400 on India’s air quality index, which is the highest rating possible.

Similar to prior years, the increase in pollution forced some local governments to shut schools and tighten regulations on building. The haze that results from weak breezes and sluggish atmospheric conditions may raise pollution levels many times over WHO guidelines.

According to Jethva’s data, stubble-burning activity was mild in Punjab and Haryana in 2025 when compared to previous years. While fire counts were fewer than in 2023, 2022, and 2021, they were higher than in 2024, 2020, and 2019.

A similar change in time has been independently discovered by Indian researchers. According to a 2025 research in Current Science, Meteosat Second Generation satellite measurements revealed that peak fire activity shifted from about 1:30 p.m. in 2020 to around 5:00 p.m. in 2024. A multi-satellite investigation published in December 2025 by experts at the International Forum for Environment, Sustainability & Technology came to the same result.

Although it is well known that stubble burning contributes to Delhi’s air pollution, experts are still debating how much of the problem is caused by crop fires compared to other causes including automobiles, industry, home heating and cooking, fireworks, and dust storms. According to studies, contributions range between 10 and 50 percent, according to NASA research scientist Pawan Gupta, who specializes in air quality.

According to Gupta, during peak episodes, stubble burning contributes 40–70% of pollution on a single day; on average, this percentage drops to 20–30% over a month, and to less than 10% on a yearly basis. “During the burning season, meteorological conditions like low temperature and a shallow boundary layer height add extra complexity,” he added.

Because evening burning may coincide with weaker winds and a thinner boundary layer, enabling pollutants to deposit more effectively, scientists speculate that the later timing of fires may have an impact on how pollution builds up overnight.