The story so far: The Indian Meteorological Department (IMD) on Monday announced that India will see more than average heat wave days in this year’s hot weather season (April to June). Above-normal temperatures are likely to be recorded over most parts of the country, and the heat is predicted to impact the southern peninsula, central India, east India, and the northwestern plains the most.
The announcement comes even as India is already struggling to keep up with its power demand, which increases significantly during summer season. A Reuters analysis reported that India’s hydroelectricity output fell at the steepest pace in at least 38 years in the year ending March 31, 2024. Hydroelectric output will possibly remain low in the coming months as well, leading to a greater dependence on coal at a time when India has, in its Nationally Determined Contributions under the Paris Agreement, promised to reduce the emissions intensity of its GDP by 45% by 2030, compared to the 2005 level.
What does the forecast say?
The IMD forecast for hot weather has said most of India, barring parts of the east and the northeast and some pockets in the northwest, will experience above-normal maximum and minimum temperatures. This can cause heat-related illnesses in people as well as affect agricultural output, cause water scarcity, increase the demand for energy, and affect ecosystems and air quality.
April, specifically, is likely to have more than the usual number of heat wave days over parts of the southern peninsula, northwest central India, east India, and the northwest plains.
The El Niño event, which causes weak rainfall and more heat over India, has weakened since the beginning of the year, the forecast noted. However, moderate El Niño conditions still exist over the equatorial Pacific, resulting in an increase in the sea surface temperature. The heat redistribution affects airflows above the ocean. Since the Pacific Ocean covers almost a third of the earth, changes in its temperature and subsequent changes in wind patterns can disrupt weather worldwide.
January 2024 was the warmest January in 175 years, the U.S. National Oceanic and Atmospheric Administration noted. The average global land and ocean surface temperature was also 0.04 degrees C higher than the previous highest, in 2016.
The El Niño is however is likely to weaken during the upcoming season and eventually turn ‘neutral’. Some models have even predicted the possibility of La Niña conditions developing during the monsoon, which can intensify rainfall across South Asia, particularly in India’s northwest and Bangladesh.
What is a heat wave?
A period of abnormally high temperatures is called a heat wave. The IMD declares a heat wave if the maximum temperature of a weather station reaches at least 40 degrees C in the plains and at least 30 degrees C in hilly regions, with a departure of around 4.5-6.4 degrees C from the normal maximum temperature. The IMD can also declare a heat wave if the actual maximum temperature crosses 45 degrees C, and a ‘severe heat wave’ if it crosses 47 degrees C.
Qualitatively, a heat wave can also occur when the temperature of the air becomes fatal to the human body.
Heat waves in India are typically recorded between March and June, and tend to peak in May.
What is causing an increase in heat wave days?
A study published in the journal PLOS Climate in April 2023 found heat waves all over the world are getting more “recurrent, intense and lethal” due to climate change. Data from April 2022 used in the study also showed abnormal temperatures caused due to climate change could have a severe impact on over 90% of India.
An increase in the number of heat-wave days and their intensity can exact steep costs from India’s public healthcare as well as agricultural output, thus affecting livelihoods, food production, disease spread, and more, the study noted.
Higher temperatures can affect human health by causing heat stress and even death, according to the World Health Organisation. A multi-city study conducted in India between 2008 and 2019 found a strong link between heat wave impact and daily mortality.
The ongoing El Niño weather condition also contributes to higher-than-usual temperatures, driving an increased occurrence of heat waves.
Elections and heat waves
Starting April 19, nearly a billion people around India will be eligible to vote in the general elections this year. The exercise will be conducted in seven phases until June 1, coinciding with India’s summer and the possibly several heat waves. The Election Commission of India has issued an advisory to manage the impact of heat waves during voting, including carrying a water bottle and protecting oneself from direct sunlight.
The heat itself can be deadly outside a heat wave if the wet bulb temperature crosses 30-35 degrees C. The wet bulb temperature is the lowest temperature to which a surface can be cooled by water evaporating from it. In other words, it’s the lowest temperature to which the surface of the skin can be cooled by sweating. Beyond this threshold, even short periods spent idling in ambient conditions can have deadly health effects.
