Heatwaves in India: Understanding the Impact of El Niño and La Niña

As temperatures soar across India, the phenomenon of heatwaves has become an alarming and increasingly frequent occurrence. In recent years, heatwaves have not only disrupted daily life but have also posed significant risks to public health, agriculture, and the economy. To fully grasp the dynamics behind these extreme weather events, it is essential to explore the roles of El Niño and La Niña—two significant climate patterns that have profound impacts on global weather, including heatwaves in India.

Heatwaves are extended periods of excessively hot weather, which may be accompanied by high humidity, particularly in oceanic climate countries. In India, a heatwave is typically defined by temperatures that are significantly above the average for a particular region and season. The India Meteorological Department (IMD) classifies a heatwave when the maximum temperature exceeds 40°C in the plains, 37°C in coastal areas, and 30°C in hilly regions. If the departure from normal temperature is more than 4.5°C, it is termed a heatwave; if it is more than 6.4°C, it is called a severe heatwave.

Heatwaves can have devastating effects on human health, leading to heat exhaustion, heatstroke, and even death. Vulnerable populations, including the elderly, children, and those with pre-existing health conditions, are at higher risk. In addition to health impacts, heatwaves strain water resources, reduce agricultural productivity, and increase the likelihood of wildfires. The economic consequences are substantial, with losses in labor productivity and increased energy demand for cooling.

El Niño and La Niña: Climate Drivers

El Niño and La Niña are opposite phases of the El Niño-Southern Oscillation (ENSO) cycle, a naturally occurring phenomenon that involves fluctuating ocean temperatures in the equatorial Pacific. These phases have significant impacts on global weather patterns, including those in India.

El Niño: El Niño is characterised by the warming of sea surface temperatures in the central and eastern Pacific Ocean. This warming disrupts normal weather patterns, often leading to warmer-than-average temperatures globally. In India, El Niño is typically associated with weaker monsoon rains and higher temperatures. This combination can exacerbate heatwave conditions, particularly in regions already prone to high temperatures. During an El Niño event, the altered atmospheric circulation can cause the subtropical jet stream to shift, influencing the distribution of heat and moisture across India. The result is often a prolonged period of higher-than-normal temperatures, leading to more frequent and intense heatwaves.

La Niña: La Niña, on the other hand, is characterised by cooler-than-average sea surface temperatures in the central and eastern Pacific Ocean. This phase generally leads to enhanced rainfall and cooler temperatures in many parts of the world. However, in India, La Niña is typically associated with stronger monsoon rains and sometimes even colder winters. While La Niña tends to mitigate the frequency of heatwaves by contributing to cooler and wetter conditions during the monsoon season, its influence is complex. La Niña can lead to extreme weather events, such as severe flooding, which can indirectly affect the climate dynamics and subsequent temperature patterns. 

Recent Trends and Future Projections

The frequency and intensity of heatwaves in India have shown an increasing trend over the past few decades. According to the IMD, the number of heatwave days in India has increased significantly, with the period from 2010 to 2020 witnessing some of the hottest years on record. This increase can be attributed to a combination of natural variability, including ENSO cycles, and anthropogenic climate change. 

Climate models project that heatwaves will become more frequent and severe in the coming years. The Intergovernmental Panel on Climate Change (IPCC) has highlighted that global warming is likely to increase the duration, frequency, and intensity of heatwaves globally, including in India. This projection underscores the urgent need for adaptive strategies to mitigate the adverse impacts of heatwaves.  

As climate change continues to amplify the frequency and intensity of heatwaves, India must adopt comprehensive strategies that include urban planning, early warning systems, public health interventions, and agricultural adaptations. Furthermore, global cooperation and adherence to international climate agreements are essential to addressing the underlying causes of climate change. The increasing threat of heatwaves is a stark reminder of the need for resilience and proactive measures. By leveraging scientific understanding and fostering community engagement, India can better prepare for and mitigate the impacts of heatwaves, ensuring a safer and more sustainable future for its citizens.