World Environment Day: Why Is It So Hot? Why Are Heatwave Spells on the Rise?

In March, when fans are usually not used much, parts of the country saw a heatwave. Why is it so hot?

'Heatwave' is the new buzzword in the dictionary of climate change.

Photo: The Quint

Video Editor: Abhishek Sharma

Camera: Athar Rather

The Climate Change Dictionary is all about breaking down all the climate jargon and the new buzzword is 'heatwave'.

It's still March, the month when fans are still on low, plans of cleaning the coolers are being made, as the creative advertisements of prickly heat powders and beverages have just started being displayed on your TVs.

However, this year, some parts of the country are already facing 'heatwaves'.

But why is it so hot?

What Are Heatwaves?

A heatwave is a period of unusually hot weather that typically lasts two or more days. To be considered a heatwave, the temperatures have to be outside the historical averages for a given area.

This means temperatures soar so high that they can kill people. The number of people dying due to heatwaves is increasing each year.

According to a study done over 20 years, more than five million people die each year across the world due to extreme temperatures. And half of such victims are in Asia.

This should concern us because India has recorded 12 of its 15 warmest years so far in the last decade and a half.

Deaths caused by heatwaves have always been less than those caused by cold waves. But that is changing now.

Why? No drumrolls needed, it’s climate change.

Both, Heat and Cold Waves Are Increasing

More than a third of heat-related deaths are caused by the warming of the globe due to anthropogenic activities, ie human-induced climate change.

This is not to say that cold waves are not happening. They are getting worse too and the number of deaths due to cold waves is increasing as well.

Due to global warming both the heat and the cold will get worse.

How Are Heatwaves Formed?

Hot air is not always a heatwave, a heatwave happens when this hot air gets trapped.

To understand this, let’s quickly revise our fifth standard science lesson. Why are ACs mostly installed on the top of the room? Because hot air is lighter and it goes up, like in a hot air balloon. And cooler air is heavier, so it settles down.

This movement creates a current and circulates the air.

Sometimes when the air creates a high-pressure system, this hot air fails to rise from the ground and gets trapped. This trapped air creates heatwave.

And usually when it gets hot, the hot air rises, it rains and the heat breaks. But when the air can’t rise, there is no rain, and it gets very hot.

In India, as seasons change from winters to summers, March is when it begins to get a little hot, but this is limited to a few states only. This year the expanse was larger. Geographically more landmass heated up. Trapping this air and causing a heatwave.

And then it didn’t rain either because of the reasons I just explained and this lack of pre-monsoon showers, further added to the already high temperatures.

Climate Change Gets Worse as the Global Heat Worsens

The frequencies of heatwaves have increased across the globe from Sub-Saharan Africa to Antarctica.

Emission of greenhouse gasses, pollution, and deforestation, among other human activities that are detremental to nature, has led to the rise in the temperature of the globe.

Currently, we are at 1.1 degrees celsius above the pre-industrial levels. This has already led us to where we are now. If the global temperature rises by 1.5 degrees celcius, 14 percent of the Earth’s population will be exposed to severe heatwaves at least once every five years.

If the global temperature rises by 1.2 degree Celsius, an extra 1.7 billion people will be exposed to severe heatwaves at least once every five years.

And if it rises by 3 degrees Celsius, the global average annual chance of having a major heatwave will increases from 5 percent to 80 percent.

The countries of the globe have been trying for a long time to limit these temperatures. The current goal is to stop it at 1.5 degrees celcius.

While it seems too distant it is already impacting you. Your electricity bill this month will be a not so gentle reminder of the same. It is impacting your fashion, your vacation, and even your choice of prickly heat powder.