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Journalism of Courage
— Abhinav Rai
(The Indian Express has launched a new series of articles for UPSC aspirants written by seasoned writers and scholars on issues and concepts spanning History, Polity, International Relations, Art, Culture and Heritage, Environment, Geography, Science and Technology, and so on. Read and reflect with subject experts and boost your chance of cracking the much-coveted UPSC CSE. In the following article, Abhinav Rai, a Doctoral researcher working on the impact of climate change on glacier dynamics in the Himalayan Region, analyses the main reasons for the above normal temperatures India experienced in November 2024.)
The month of November in 2024 was the second warmest November in 123 years in India, underscoring the escalating impacts of climate change on ecosystems and threatening food security by disrupting the growth of rabi (winter) crops.
This warming trend has continued since the post-monsoon season in October, and could contribute to making 2024 the warmest year ever on record, globally. But what were the main reasons behind the above normal temperatures and what this means for India and the world?
Meteorologists use a minimum of 30 years of climate data to derive any conclusion about deviations of climatic parameters from their ‘normal’ values. At present, the India Meteorological Department (IMD) uses 1991-2020 as the base period.
In its ‘Monthly Climate Summary’, IMD reported an average maximum temperature of 29.37ºC in November 2024, 0.62ºC above the normal 28.75ºC. The average monthly minimum temperatures, too, were high in November 2024, with a deviation of 1.05ºC above the normal mark of 15.86ºC.
IMD’s precipitation data also shows that the country received 55 per cent less rainfall (13.5 mm) in November 2024, against the long-period average (LPA) of 29.7 mm. The northwest region of India faced the worst deficit, with 79.87 per cent less rainfall.
One of the primary reasons for this elevated temperature and rainfall deficiency is the absence of strong western disturbances, as they bring rain and cooler air to northern and northwest parts of India during this time of the year. The lack of cyclonic disturbances (low pressure systems or likewise) was yet another reason behind the lowest rainfall activity across the country.
There were only two low pressure systems that developed in the Bay of Bengal, with one intensifying into Cyclone Fengal. However, Fengal also did not provide rainfall, which was expected. These factors combined led to the prolonged dry spell, resulting in a warmer November overall for the country. Let’s delve deeper into the phenomena of Western Disturbances and why they are so important.
IMD defines western disturbances as low-pressure cyclonic weather conditions in mid and lower tropospheric levels. It formed mainly over the Mediterranean Sea, Caspian Sea and Black Sea regions. It is carried eastward by the subtropical westerly jet streams and reaches the Indian sub-continent. When these western disturbances encounter the Himalayas in northwestern India, they shed their moisture in the form of snow and rain.
Thus, western disturbances are non-monsoonal precipitation systems driven by westerly winds. They are called extra-tropical cyclones due to their origin in mid-latitude regions, north of the Tropic of Cancer, and exhibit frontal characteristics. These western disturbances are most active during November and March and bring precipitation mainly in the northwestern part of India, Pakistan and Afghanistan.
Sometimes, they even extend to the Northern plains and deliver much-needed winter rainfall. This precipitation is essential for the Rabi crop cycle and helps mitigate water scarcity in arid regions. During peak winter months (December to February), India can experience 6-7 western disturbance spells per month.
The term “Western Disturbance” was first used by S.L. Malurkar in 1947 to describe these systems’ west-to-east trajectory concerning India. This phenomenon was earlier called ‘Winter Disturbance’.
India is a country with a huge geographical diversity. Even though the country’s main source of precipitation is the southwest monsoon, its spatial coverage is not uniform. Western Himalayan states and Union Territories (UTs) rely on western disturbances for winter precipitation. Precipitation spells brought by western disturbances are very crucial for the Rabi crops such as Wheat, Gram, Mustard, etc., in the states of Punjab, Haryana and Western Uttar Pradesh.
Around 30 per cent of the winter precipitation in Jammu & Kashmir, Ladakh, Himachal Pradesh, Punjab, and Uttarakhand is caused by western disturbances. Strong western disturbances often bring heavy seasonal snowfall to these regions, which helps sustain regional snowpack and replenish the water resources.
Snowfall occurring at higher elevations in sub-zero conditions does not melt easily and thus feeds glaciers, contributing to the perennial rivers that support the irrigation and drinking water needs of downstream communities. Western disturbances can also affect the albedo (reflectivity) of the Himalayas and Tibetan Plateau, which regulates the onset of the Indian summer monsoon.
However, western disturbances can also have negative impacts. When strong western disturbances occur, they sometimes cause dense fog and severe cold wave conditions in northern plains. Very heavy snowfall events or hailstorm-like conditions sometimes damage crops and increase the risk of landslides and avalanches.
The unusually warm November of 2024 has significant implications for both India and the world. According to the Copernicus Climate Change Service, November 2024 was the second warmest November globally, with an average temperature being 14.10ºC, which is 0.73ºC above the monthly average.
Sea ice levels also reflected this warming trend. Antarctic Sea Ice has witnessed its lowest extent for November 2024 – 10 per cent below the average. Similarly, Arctic Sea ice also saw its third-lowest area coverage, with its extent reducing 9 per cent below the average.
In India, the warm November aligns with the broader global warming trend that could make 2024 the hottest year on record. These changes are indicative of larger shifts in global and regional climatic patterns. This warming trend can reduce seasonal snow cover and sea ice, leading to extreme events that can alter the ecosystem’s balance.
The lack of rainfall and cyclonic activity induced by changes in the western disturbances activity could negatively impact the winter crops in the northern part of the country. These crops depend on western disturbances for required precipitation and associated cold weather conditions.
Therefore, the warm November serves as a stark reminder of the urgency to address climate change, as it affects the delicate balance of ecosystems, posing a threat to biodiversity and livelihoods.
What were the main climatic and atmospheric factors responsible for the second warmest November in 123 years in India?
How does the warming trend of November 2024 impact the growth of rabi crops and threaten food security in India?
What are the broader implications of above-normal temperatures for ecosystems and biodiversity globally?
In what ways can the global and regional temperature rise of November 2024 influence extreme weather events?
What measures can India take to mitigate the impacts of warming trends on agriculture and ecosystems in the future?
(Abhinav Rai is a Doctoral candidate at the Department of Geography, Delhi School of Economics, University of Delhi.)
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