As May nears its end, much of North and Central India is already experiencing a severe heatwave. On Wednesday, several regions in Delhi and Rajasthan reported temperatures exceeding 50 degrees Celsius. However, after a shower on Wednesday evening, Delhi's temperature dropped to 41.8 degrees Celsius on Thursday. Meanwhile, Mumbai recorded 33 degrees Celsius, Bangalore 30.4 degrees Celsius, and Chennai 39 degrees Celsius.
India's metropolitan areas typically register higher temperatures in May, June, and July, a phenomenon attributed to the urban heat island effect. This effect causes cities to be significantly warmer than their rural surroundings.
What is the Urban Heat Island Effect?
The urban heat island effect occurs when urban regions record higher temperatures than their rural surroundings. This happens mainly due to human activities, buildings, and infrastructure in urban areas that absorb and retain heat more effectively than natural landscapes.
Global Warming and El Nino
Rising temperatures are a global issue, and the situation is worsening worldwide. Scientists suggest that one reason for India's excessive heat is the El Nino effect, which alters global weather patterns.
What is the El Nino Effect?
El Nino is characterized by unusually warm ocean temperatures in parts of the Pacific Ocean, leading to a rise in sea surface temperatures. The El Nino cycle began in 2023 and is expected to last until June this year. This phenomenon has contributed to the extreme summer in India. However, as El Nino weakens, La Nina is expected to follow.
What is the La Nina Effect?
La Nina involves the cooling of water in the Pacific Ocean and occurs at irregular intervals. It is associated with widespread changes in weather patterns. Once La Nina takes effect, India is likely to experience a good monsoon this year.
Causes of Heatwaves
Various changes in our atmosphere and oceans contribute to heatwaves in North Central and Eastern India. Heatwaves are particularly dangerous as they cause heat stress in our bodies.
Dry Heat Stress: This occurs when temperatures rise while humidity remains low, making it difficult for the body to cool down through sweating. This can lead to dehydration and other health issues. Central and North Western India, with less summer humidity, faces more dry heat stress cases.
Moist Heat Stress: This occurs when high temperatures combine with high humidity, also hindering the body's ability to cool down through sweating. Eastern coastal areas like Odisha, Andhra Pradesh, Tamil Nadu, and Maharashtra experience more moist heat stress during high-temperature monsoon seasons.
A recent study by the India Meteorological Department (IMD) revealed a 30% increase in heat stress cases in India over the last 40 years (1980-2020), primarily due to rising temperatures combined with humidity. During this period, the average heat index in Central India, North West India, and Eastern coastal areas saw temperatures rise 4 to 5 degrees Celsius above the normal summer average
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