EXTREME HEAT EVENTS IN INDIA #upsc #prelims #mains #environment #climatechange

A heatwave refers to surface temperatures being significantly higher than normal for several days at a time.The World Meteorological Organization defines heatwaves as “five or more consecutive days during which the daily maximum temperature surpasses the average maximum temperature by 5°C (9°F) or more”.However, there is no universally accepted definition for heatwaves. Heatwaves are measured relative to the usual weather in an area and the normal temperatures for the season, and so definitional differences are reflective of global climatic variations and the geographically variable nature of heatwaves and their impact. Several countries have adopted their own standards on heatwaves. The India Meteorological Department requires that temperatures should reach at least 40°C in the plains and at least 30°C in the hilly regions, and should reflect an increase of at least 5°C-6°C (or 9°F-10.8°F) above the normal temperature to be classified as a heatwave.The US National Weather Service defines a heatwave as a spell of “abnormally and uncomfortably hot and unusually humid weather” over two days or more.In Denmark, a heatwave occurs when the mean of the highest recorded temperature measured over three consecutive days exceeds 28°C (82.4°F). In Adelaide, Australia, a heatwave is defined as five straight days with temperatures at or above 35°C (95°F), or three consecutive days at or over 40°C (104°F).Heatwaves “may be characterized by low humidity, which may exacerbate drought, or high humidity, which may exacerbate the health effects of heat-related stress, which include heat exhaustion, dehydration and heatstroke”.Experts identify two facets to a heatwave—the physiological (centred on the general thermoregulation of the human body) and the sociological (focused on local adaptations to the climate). “The human thermoregulatory mechanism endeavors to maintain a constant core temperature for the body, which commonly requires that the internal heat generated by metabolism be transferred through the skin and, to a much lesser extent, the lungs to the surrounding atmosphere”.If the atmospheric conditions are such that the removal of body heat is hampered (as it may be during extreme heat events), the body’s core temperature will likely rise and cause health problems, and may culminate in death. Heatwaves are a global phenomenon; around the world, days are getting hotter more frequently. The proportion of the Earth’s surface area that was subjected to scorching summers (significantly higher than the average temperatures) increased from 1 percent between 1951-80 to over 10 percent between 1981-2010.Record-breaking heat events were experienced in Australia, Argentina, China, Central Asia, large parts of Europe, Mexico, Japan, South Korea and the US in 2016,and there will almost certainly be an increase in frequency, severity, duration and the spatial extent of heatwaves in the future. Follow my telegram channel - https://t.me/aspirantvoice. Speak to me here - https://anchor.fm/aspirant-voice/message. Do follow me on Twitter- https://twitter.com/smurali236?s=09 , Facebook - https://www.facebook.com/Aspirantvoiceupsc/ , Instagram- https://instagram.com/aspirant_voice_upsc?utm_medium=copy_link