A study by Climate Trends pointed out that while there is a slight improvement in the air situation in Delhi-NCR, the pollution level may stagnate at the 'very poor' level.

The report states that while there are several sources of pollution, meteorological factors play a vital role in the air quality. While the meteorological conditions, including good wind speed and easterly wind direction, favoured Delhi earlier this season, they are now responsible for the high AQI readings.

The report said that the early arrival of fog over the north-western plains, along with the absence of winter rain over the region, had adversely affected the air over the capital.

Professor S N Tripathi, dean, Kotak School of Sustainability, Indian Institute of Technology-Kanpur, said particulate matter changed its property when it came in contact with fog, creating conditions for more fog. "A tiny chemistry takes place here when particulate matter gets oxidised in contact with fog.

There is a strong relation between oxidised particulate matter and fog condensation nuclei as compared with non-oxidised components," explained Tripathi. "In fact, smaller droplets oxidise faster and oxidised PM is more efficient in forming more fog. All these conditions result in a vicious smog circle, in which we will not see the fog clearing for days, and that is what we have witnessed in the last few days."

Experts also cited a definite influence of climate change in the deterioration of air quality. "Delhi and the adjoining areas have already been struggling with changing climatic conditions. Climate change and unfavourable meteorological conditions have multiplied the impact of pollution," said professor Sagnik Dey, Centre for Atmospheric Sciences, IIT-Delhi. "Not only have winter rains become erratic, but climate change has also altered the frequency and intensity of the western disturbances, which are the primary source of rain over the northern plains," said Dr Dey.

"A further rise in global average temperature will worsen the situation as we do not have control over changing meteorological conditions. Controlling emissions is the need of the hour, else pollution will increase manifold."

On Thursday, there was a slight improvement in the air quality, though AQI stalled at the ‘very poor' level, having remained at ‘severe' for five straight days. "No one single source of pollution is responsible for this," noted Aarti Khosla, director, Climate Trends. "There are many sources, including black carbon, ozone, fossil burning, harvest stubble burning, etc.

We need to evaluate how much each source is contributing and look for solutions. We need to urgently respond to the realities of climate change that the world is facing today."

Another study, by Respirer Living Sciences, highlighted severe pollution levels concentrated in Indo-Gangetic Plains and the northern and central Indian regions, with Delhi emerging as the most polluted city. The study highlights the significant role of regional and seasonal factors in exacerbating air pollution.