A recent study has found that the number of people in India exposed to extreme levels of humid heat during the monsoons has increased by at least 670 million between 1951 and 2020. The researchers examined trends in hot and humid conditions, known as 'moist heat extremes,' typically observed during the summer monsoon months, using the Wet-Bulb Globe Temperature (WBGT) metric.
The researchers, including those from Cornell University in the US, discovered that the area exposed to extreme and detrimental wet-bulb temperatures exceeding 31 degrees Celsius has increased by nearly 43 million square kilometers, affecting over 670 million people.
“The consistent increase in exposed area (of close to 43 million square kilometres above 31 degrees Celsius can adversely impact the labour-intensive work during the monsoon break,” the authors wrote in the study published in the journal Earth’s Future.
The study also revealed that the regions most vulnerable to moist heat extremes, with wet-bulb temperatures exceeding 38 degrees Celsius, were primarily located along the Indo-Gangetic plain and the eastern coast.
“The increase in moist heat can directly impact about 37-46 million people living over the Indo-Gangetic plain,” the authors wrote. The humid and hot conditions during monsoons are a significant challenge to the health and well-being of the people of India, especially to physical labour, the researchers said.
Extremes due to high humidity have been observed in recent times, largely driven by global warming. According to the authors, prolonged exposure to such conditions can result in potentially fatal health hazards. For the study, the researchers used data from the ERA5 dataset, which provides hourly estimates of temperature, humidity, and wind speeds.