Intense heat waves in different parts of India and its implications

• India is in the throes of an unusually long series of heatwaves that began in the end of March and scorched north India for most of April.
• The India Meteorological Department (IMD) said April was the hottest in northwest India in 122 years.

Extent of heatwave

• Records from IMD suggest that the average maximum temperature till April 27 was 35.7 degree Celsius, the highest in five years for this month.
• In most of these States, the temperature has been consistently above 42 degree Celsius and around 5-6 degrees above normal for this time of the year.
• While it is not unusual for the latter half of April to be dry and hot in most of north, west and central India, this year is unusual in that this follows the warmest March in 121 years with the maximum temperature across the country nearly 1.86 degree Celsius above normal.

Conditions for declaration of Heat waves

• A heatwave is declared when the maximum temperature is over 40 degree Celsius and at least 4.5 notches above normal.
• A severe heatwave is declared if the departure from normal temperature is more than 6.4 degrees, according to the IMD.
• Based on absolute recorded temperatures, a heatwave is declared when an area logs a maximum temperature of 45 degree Celsius.
• A severe heatwave is declared if the maximum temperature crosses 47 degrees.

Role of Climate Change

• The heat-trapping consequences of global warming imply that climate extremes such as heatwaves are expected to rise in frequency.
• Instances of extreme rainfall, as well as longer rainless spells are expected, according to assessments by the Intergovernmental Panel on Climate Change.
• The main reason for the scorching heat in the northern parts of the country is lack of rainfall.
• Usually, periods of high temperature are punctuated by periodic episodes of rain but this was largely absent during March and April.
• Ironically, April also saw maximum instances of extreme rainfall since 2018 though it was concentrated in the south and north-eastern India.
• The rain-bearing western disturbances originate because of temperature gradients between the northernmost parts of the globe and the latitudes passing through West Asia.
• Weaker gradients mean weaker rains.
• This March and April, cooler than normal conditions in the Pacific Ocean failed to aid rainfall in north India.

Impacts of heatwaves over India

• Research through the years shows that the number of heatwave days in India is increasing every decade.
• Some parts along eastern India, such as Andhra Pradesh, Telangana and Odisha, also register higher humidity along with high temperatures, leading to a rise in a condition called ‘wet bulb’ temperature, that at its mildest can cause extreme discomfort and at its worst cause dehydration and death.
• Heatwaves have killed more than 17,000 people in 50 years in India, according to a research study by IMD scientists.
• However, the intensity and length of heatwaves don’t have a direct connection to India’s monsoon that sets in over Kerala in June.

Steps taken to make a buffer against high temperatures

• Improved forecast systems that allow heatwave warnings to be disseminated via electronic channels and phones instantaneously.
• Declaration of school holidays by many State governments across the country.
• Highlighting the dangers of working outdoors during the day.
• Monetary compensation for deaths linked to heatwaves by state governments.

Exam Track

Prelims Takeaway

• Heat wave
• IMD

Mains Track

Q March was warmest ever in 121 years with the maximum temperature across the country nearly 1.86 degree Celsius above normal. In the light of this discuss about heatwaves and its severe impacts and role of climate change in it.