The highest minimum temperature refers to the warmest low temperature recorded during a specific period, typically within a 24-hour cycle. This metric is crucial in understanding the persistence of heat in a given location, as it indicates how much the temperature drops, or fails to drop, during the cooler parts of the day, often nighttime. High minimum temperatures are significant because they can exacerbate heat stress on populations, as they provide little relief from daytime heat, and can influence energy consumption, agricultural productivity, and public health. Tracking these temperatures is particularly important in the context of climate change, where rising global temperatures are contributing to more frequent and intense heatwaves.
Tags: GS-3, Ecology & Environment – Heat
Context:
- Delhi faced unprecedented minimum temperatures and prolonged heatwave conditions, exacerbated by climate change and urbanisation.
- The highest minimum temperature between 1969 and 2024 was 34.9 degree Celsius recorded on May 23, 1972.
Highest Recorded Minimum Temperature:
- Delhi registered its highest minimum temperature since at least 1969 on Tuesday, reaching a scorching 35.2 degrees Celsius.
- This record is alarming as it comes after a stretch of already elevated temperatures, marked by seven heatwave days in June thus far.
- Adding to the concern, the city has endured six consecutive warm nights, with temperatures staying above 40 degrees Celsius since May, underscoring the persistence of intense heat conditions through the night.
Warm Nights:
- According to IMD criteria, a warm night is defined when the minimum temperature exceeds normal levels by 4.5 to 6.4 degrees Celsius.
- If the departure from normal exceeds 6.4 degrees Celsius and the daytime temperature is 40 degrees Celsius or higher, it qualifies as a severe warm night.
- In Delhi’s recent example, the minimum temperature was 8 degrees above normal, reaching 35.2 degrees Celsius, highlighting an extreme deviation from typical nighttime temperatures.
The concerns surrounding the recent warm nights in Delhi are multifaceted and critical:
Impact on Health:
- The human body typically experiences relief from daytime heat during the night, especially between 3 am and 5 am.
- However, due to the recent warm nights where temperatures haven’t significantly dropped, there’s a lack of this essential relief.
- This situation is a major health concern as prolonged exposure to high temperatures can lead to heat-related illnesses, including heatstroke.
Rain Deficit and High Temperatures:
- Delhi and its surrounding areas are facing a rain deficit of over 90%, exacerbating the heatwave conditions.
- With daytime highs consistently exceeding 40°C, the combination of high temperatures and lack of nighttime cooling poses significant health risks to the population.
Rise in Heat Stroke Cases:
- Despite the peak daytime temperatures occurring in late May, doctors are reporting an increase in heat stroke cases.
- This rise is directly attributed to the lack of nighttime relief, where warmer temperatures make it difficult for people to cool down indoors, forcing them outdoors during the day and into warmer spaces at night.
Data and Trends:
- In June 2024, Delhi witnessed 12 days with minimum temperatures above 30°C, the first occurrence since 2011.
- This trend underscores a shift towards warmer nights, which is unusual and indicative of changing climate patterns affecting the region.
Urban Heat Island (UHI) Effect:
- The Urban Heat Island effect exacerbates nighttime temperatures in urban areas like Delhi.
- Urban structures such as concrete buildings and roads absorb and re-emit heat, contributing to higher temperatures compared to surrounding rural or less urbanised areas.
- The reduced greenery further intensifies this effect, particularly during nighttime when the absence of vegetation fails to mitigate the heat through natural cooling mechanisms like evapotranspiration
Urban heat dynamics:
Temperature Variations in Delhi:
- Areas adjacent to the Ridge and greener spaces like Lutyens’ Delhi experience lower temperatures compared to densely urbanised areas.
- The temperature variations can range from 2 to 4 degrees Celsius over short distances of a few kilometres.
- This disparity underscores the impact of urbanisation and green cover on local temperature conditions.
Centre for Science and Environment (CSE):
- A study conducted by the Centre for Science and Environment (CSE) examined temperature data from major Indian cities spanning the period from 2001 to 2024.
- The findings suggest that there has been a noticeable trend of slower cooling rates in recent years.
- This phenomenon contributes to warmer nighttime temperatures overall in urban areas.
Source: IE
1. What is meant by the “highest minimum temperature”?
Answer: The “highest minimum temperature” refers to the highest low temperature recorded in a 24-hour period. It indicates the lowest temperature reached during the night or early morning that is still significantly high, which can be indicative of heatwaves or unusual climatic conditions.
2. Why is the highest minimum temperature significant?
Answer: The highest minimum temperature is significant because it can indicate prolonged periods of heat, which can be more harmful to health than high daytime temperatures alone. Consistently high minimum temperatures prevent the environment from cooling down, contributing to heat stress for humans, animals, and plants, and can also impact energy consumption due to increased use of cooling systems.
3. Which regions are most likely to experience high minimum temperatures?
Answer: Regions most likely to experience high minimum temperatures include tropical and subtropical areas, urban heat islands, and arid regions. Cities tend to have higher minimum temperatures due to the heat island effect, where buildings, roads, and other infrastructure absorb and re-radiate heat.
4. What was the highest minimum temperature ever recorded?
Answer: As of recent records, the highest minimum temperature ever recorded was 42.6°C (108.7°F) in Quriyat, Oman, on June 26, 2018. This extreme low temperature highlights the severity of heatwaves in certain parts of the world.
5. How do high minimum temperatures affect human health?
Answer: High minimum temperatures can exacerbate heat-related illnesses such as heat exhaustion and heatstroke, particularly because they do not allow the body to cool down sufficiently during the night. This can lead to increased mortality and morbidity rates, especially among vulnerable populations such as the elderly, children, and those with pre-existing health conditions. Additionally, high nighttime temperatures can disrupt sleep, further impacting overall health and well-being.
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