Increase in Humid Heat

(Preliminary Exam: Geography of India and the World)
(Mains Exam, General Studies- 3: Important Geophysical Events and Geographical Features, Changes in Flora and Fauna and the Effects of Such Changes, Disaster and Disaster Management)


According to a research, the number of people affected by extreme levels of humid heat during monsoon in India has increased by at least 67 crores between the year 1951 and the year 2020. 

Key Points of Research Findings

  • According to the research, the area with extreme and harmful wet-bulb temperatures above 31 degrees Celsius has increased by about 43 million sq km.
    • In fact, this area includes more than 67 crore people.
  • The continuous increase in humid heat can adversely affect labor-intensive work during the monsoon.
  • According to scientists, the most vulnerable regions to extremes of humid heat with wet-bulb temperatures above 38°C were mainly the Indo-Gangetic plains and the east coast.
    • In fact, an increase in humid heat could directly affect about 37-46 million people living in this region. 

Wet-bulb globe temperature

The wet-bulb globe temperature (WBGT) parameter estimates the effect of temperature, relative humidity, wind and solar radiation on humans.

  • Global warming has caused a 10% increase in the number of hot and humid extreme days between 1951 and 2020.
  • Also, the average relative humidity (RAH) has increased significantly during the last ten summer seasons compared to the average of 2001-10.
  • The average relative humidity has increased by 5% to 10% in other metropolitan cities except Bengaluru.
    • In fact, in dry areas like Hyderabad, the relative humidity has increased by 10% compared to 2001-2010, while in Delhi it has increased by 8%.
    • Mumbai, Kolkata and Chennai still show 25% more humidity than Delhi and Hyderabad. 

What is humid heat?

  • Humid heat refers to the increased transformed heat resulting from the combination of high temperature and humidity.
    • Humid heat is actually produced due to high temperature and high level of humidity in the air.
  • Therefore, in such a situation, the sweat of the body does not evaporate easily, due to which it becomes difficult to cool the body.
    • As a result, humid heat is comparatively more dangerous. 

Effects of humid heat


  • It increases the state of lack of energy and lethargy. It can cause hyperthermia.
    • As a result, conditions like dehydration, fatigue, muscle cramps, fainting, nausea and sunstroke may occur. 

Labour Productivity

  • Humid heat can seriously affect labour productivity.
    • In fact, a 3°C increase in global warming can reduce labour productivity by 7% and reduce India's GDP by at least 4%.
  • As a result, researchers have emphasized the urgent need to modify outdoor working hours in areas with high humid heat conditions, especially during the monsoon. 

Meaning of Dry Heat

  • Dry heat refers to outdoor conditions in areas with high temperatures and low humidity.
  • This condition usually occurs in hot desert climates where rainfall is very low.
    • In fact, the absence of moisture in the air causes the body's sweat to evaporate more quickly.
  • In dry heat conditions, emphasis on consuming more water because the rapid evaporation of sweat can lead to dehydration.
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