What are Oppressive Heatwaves?

January 27, 2025

In recent years, researchers have focused on the increasing frequency of heatwaves in India. A study conducted by IIT-Bombay and ETH Zurich marks the phenomenon of ‘oppressive heatwaves’. These are characterised by high temperatures combined with high humidity. This combination poses health risk. The study indicates that future heatwaves will become more severe due to global warming.

Definition of Heatwaves

Heatwaves are periods of excessively high temperatures.
The India Meteorological Department (IMD) defines a heatwave as three consecutive days with temperatures exceeding specific thresholds.
In plains, this threshold is above 45 degrees Celsius. In hilly areas, it is above 40 degrees Celsius.

Types of Heatwaves

Researchers classify heatwaves into two categories – oppressive and extreme.
Oppressive heatwaves involve both high temperature and high humidity.
Extreme heatwaves occur with high temperature but low humidity.
This distinction is crucial for understanding the health impacts associated with these weather events.

Historical Data Analysis

The study utilised historical data from 1951 to 2013.
This data included daily temperature records from the IMD and other meteorological agencies.
The researchers examined the relationship between heatwave days and heat-related mortality from 1967 to 2007.
They found a strong positive correlation between oppressive heatwave days and increased mortality rates.

Future Projections

The researchers projected future heatwave occurrences under two global warming scenarios – a rise of 1.5 degrees Celsius and 2 degrees Celsius relative to pre-industrial levels.
They expect a five-fold increase in oppressive heatwave days by 1.5 degrees Celsius warming by the end of the century.
Under a 2 degrees Celsius scenario, this increase could reach eight-fold.

Health Implications

The study warns of rise in heat-related mortality due to oppressive heatwaves. As these events become more frequent, the risk to public health escalates. The researchers emphasise the need for adaptation measures to mitigate these risks.

Global Warming and Heatwaves

Limiting global warming to 1.5 degrees Celsius could reduce the likelihood of oppressive heatwaves by 44 per cent.
It could also decrease extreme heatwave occurrences by 25 per cent.
This puts stress on the importance of climate action to protect vulnerable populations.

« Previous Post Next Post »