Subtle changes in sea surface temperatures in the Pacific Ocean and oscillating wind patterns near Antarctica may influence air pollution levels over the Indo-Gangetic plains, scientists in China and the US said on Wednesday.

The scientists have found that El Nino, the rise in average sea surface temperatures over parts of the Pacific, and a belt of winds called the Antarctic oscillation can through long-distance effects influence atmospheric conditions and air pollution levels over northern India.

Their findings could help India predict winter-time air pollution conditions and initiate emissions control plans to minimise health risks from deterioration of air quality, the researchers at Hong Kong Baptist University, Nanjing University, Fudan University in China and Harvard University in the US said.

The paper was published on Wednesday in the research journal Science Advances.

Scientists have known for years that northern India is vulnerable to severe air pollution during the autumn and winter months resulting from a mix of traffic and industrial emissions, soot from burning crop-residues, and natural dust.

In their new study, atmospheric scientist Meng Gao and colleagues have shown that both El Nino and the Antarctic oscillation can induce wind conditions that could worsen air pollution levels.

During strong El Nino winters, the researchers said, wind speeds are weaker over northern India. Low wind speeds can lead to stagnation in the atmosphere and trigger spikes in pollution. The Antarctic oscillation working through effects related to the Indian ocean can also lead to conditions that increase pollution levels.

A senior Indian atmospheric physicist and an authority on winter-time air pollution said such links between distant weather conditions and air pollution levels needs to be explored further.

“We have some hints that monsoon behaviour can influence air pollution levels,” said Gufran Beig, a senior scientist at the Indian Institute of Tropical Meteorology, Pune, who was not associated with the China-US study.

Beig and his colleagues had earlier this year suggested that an extreme spike in air pollution levels over northern India during autumn-winter 2017 was likely related to an unusually late withdrawal of the monsoon that year.

The late withdrawal was followed by the emergence of a lower-than-normal anti-cyclone condition which led to low wind speeds and “stagnation” near the surface and spikes in pollution, Beig said.

The China-US research team has pointed out that under global warming, extreme El Nino conditions have been predicted to become more frequent in the years to come.

Earlier studies probing how rising global temperatures might impact pollution had predicted that air pollution windows in India are likely to increase by 20 to 120 days per year by the year 2050.