NEW DELHI: One big reason for the long spell of extreme cold weather in Delhi and many parts of North India this winter season is rising air pollution, say scientists. Delhi's air quality, which was adjudged to be the worst among world cities by the WHO
in May, worsened as winter approached because of smog and fog, caused by vehicular and factory emissions staying close to the ground in heavy cold air. And fog impacts day temperature by blocking sunshine.
"The fog keeps the day-time temperatures low, making it colder," said climate scientist Ajit Tyagi, who holds the Koteswaram chair in the ministry of earth sciences. Since mid-December, Delhi and north India have been experiencing
unusually cold weather even though there has been no appreciable dip in the minimum temperature.