Extreme temperature events including heat waves, warm spells, cold waves and cold spells, are directly impacted by global warming. According to the Indian Meteorological Department (IMD), Cold wave is considered when the minimum temperature of a station is 10°C or less for plains and 0°C or less in hilly regions. Cold waves have a serious effect on human health, varying from cough and cold, bronchitis and respiratory diseases, blood pressure issues, skin problems, and even Bone, joint, and muscle pain due to lack of sunlight. The health conditions, particularly of the poor people, are seriously affected, and in extreme cases even it causes casualty.
Cold waves are majorly caused by two natural patterns rendered more extreme by climate change. La Nina is a climate pattern that causes cold winters in Northern countries. The second pattern is the Polar Vortex. It brings cold air from the north pole into countries situated in midlatitudes.
All populations over the world are under certain threats from non-optimal temperatures, regardless of their ethnicity, location, sex, age, and socioeconomic status. Globally, 50,83,173 deaths were associated with non-optimal temperatures per year, consisting of 45,94,098 cold-related deaths.
A number of cold spells occurred in the winter of 2020/21. Two of these events occurred over East Asia (25–31 December 2020 and 5–10 January 2021), and one occurred over North America (5–22 February 2021). The most prominent feature of each of these events is the southward extent of cold polar air reaching climatologically warmer areas, particularly in North America, breaking many historical cold temperature records.
Excess deaths are typically defined as the difference between the observed numbers of deaths in specific time periods and expected numbers of deaths in the same time periods. The highest number of cold related deaths annually are observed in Asia followed by Africa. As per the EM-DAT data, total damages due to cold waves in Asia region during the period 1961-2022 were around US$ 3193 million.
For long, India has faced some of the worst natural disasters including tropical cyclones, floods, earthquakes, lightning, heat waves and cold waves resulting in the loss of life and property, as well as adversely impacting livelihood. Intense cold wave has have become one of the most pressing worries in recent years.
In India, cold wave occurs in the month of December-January every year and sometimes extended cold wave events occur from November to February and are limited mostly to northern India. The minimum temperatures go down below 8°C over many parts of northern India during November to February months. However, December & January are the coldest months with minimum temperatures below 6°C over most parts of northwest India and below 8°C over the rest parts of northern India.
Number of deaths due to extreme weather events by regions of India, 2001-14
As per the graph shown above, the northern India has 50% of deaths due to cold waves compared to the deaths in other regions. 27% deaths are in eastern India.
As per IMD, India’s ‘Core Cold Wave Zone’ covers 17 States/UTs covering Punjab, Himachal Pradesh, Uttarakhand, Jammu & Kashmir, Ladakh, Delhi, Haryana, Rajasthan, Uttar Pradesh, Gujarat, Madhya Pradesh, Chhattisgarh, Bihar, Jharkhand, West Bengal, Odisha and Telangana. Cold wave has caused 5,530 deaths from 2000 to 2021 across various states [IMD, Ministry of Earth Sciences].
In 2023, minimum temperatures are observed in the range of 1-3°C in many parts of southwest Uttar Pradesh, south Haryana, Delhi and adjoining north Madhya Pradesh and some parts of north Rajasthan and in the range of 3-7°C over many parts of central Madhya Pradesh, east Uttar Pradesh, west Uttar Pradesh and in isolated pockets over Himachal Pradesh, Punjab, Bihar and west Madhya Pradesh [IMD].
There are several studies which confirm the relation of ambient hot/cold temperatures on human health. However in India, there studies limited to heat waves and its effect on human health. A study published in PloS Medicine highlights the fact that cold temperatures contribute to higher attributable risk of mortality than hot temperatures in India during 2001-2013. Elderly population had higher number of attributable risks than other population group in their study. Diseases like cardiovascular illness, stroke, respiratory illness including asthma and chronic obstructive pulmonary diseases gets affected by cold effects.