India and Pakistan: Prepare for even more intense heat waves


A heatwave has been hitting India and Pakistan - one of the most densely populated regions in the world - since April, forcing more than a billion people to brave temperatures well above 40C. These temperatures are not yet historic records for these regions, but the hottest time of the year is yet to come.

While the heat wave is already putting danger to people's lives, and causes bad harvests and power outages, the situation could get worse: based on what is happening elsewhere, India is destined to experience an even more intense heat wave.

Our team of climatologists recently looked at the most extreme heat waves in the world over the past 60 years, but taking into consideration deviations from expected temperatures in this area, rather than just the maximum temperature. India and Pakistan are not included in our results, published in the journal Science Advances. Although temperatures and heat stress levels are steadily rising to very high absolute levels, heat waves in India and Pakistan have not been so extreme so far compared to regional normals.

In fact, the region has a rather modest history of weather extremes. In the data we reviewed, we found no heat waves in India or Pakistan deviating more than three standard deviations compared to the average, whereas statistically, such an event would be expected once every 30 years or so. The most severe heat wave we have identified, in Southeast Asia in 1998, was five levels away from the average. Such an extraordinary heatwave in India today would be tantamount to reaching temperatures of over 50°C across large swathes of the country – such temperatures have only been seen in localized points until now.

Our work therefore suggests that India could experience even more extreme heat. Considering that the statistical distribution of daily maximum temperatures is broadly the same around the world, it is likely, again from a statistical perspective, that a record heat wave will hit India at some point; the region has not yet had the opportunity to adapt to such temperatures and would therefore be particularly vulnerable.

Harvests and health

Although the current heat wave has not broken historical records, it remains exceptional. Many parts of India have experienced their hottest april on record. Such heat so early in the year will have devastating effects on crops in an area where many depend on the wheat harvest for food and a living. Usually, extreme heat in this region is closely followed by cooling monsoons – but these won't arrive for several months.

Crops will not be the only ones affected by the heat wave, which also affects infrastructure, ecosystems and human health. The impacts on human health are complex, as both meteorological (heat and humidity) and socio-economic (lifestyle and adaptive capacity) factors come into play. We know that heat stress can lead to long-term health problems. term such as cardiovascular disease, kidney failure, respiratory distress and liver failure, but we will not be able to know exactly how many people will die during this heat wave due to a lack of health data from India and Pakistan.

What the future holds

To consider the impact of extreme heat over the next few decades, we need to look at both climate change and population growth, because it is the combination of the two that will amplify the impacts of heat waves on human health. in the Indian subcontinent.

world map with some countries shaded in yellow
Areas of significant population increase over the next 50 years (red circles), all coincide with locations where no daily mortality data exist (yellow).
Mitchell, _Nature Climate Change_ (2021), CC BY-SA

In our new study, we sought to understand how the extremes are likely to evolve in the future. By using a large set of climate model simulations, we obtained much more data than is actually available. We found that underlying global warming did not affect the statistical distribution of extremes. In climate models, daily temperature extremes increase in the same way as the average climate. the latest IPCC report indicates that heat waves will become more intense and frequent in South Asia during this century. Our results confirm this.

The current heat wave is affecting more than 1,5 billion people while the population of the Indian subcontinent is still expected increase by 30% over the next 50 years. That means hundreds of millions more people will be born in a region that is set to experience more frequent and severe heat waves. As even more people will be affected by even more intense heat waves, climate change response measures must be accelerated – urgently.

Vikki Thompson, Senior Research Associate in Geographical Sciences, University of Bristol et Alan Thomas Kennedy-Asser, Research Associate in Climate Science, University of Bristol

This article is republished from The Conversation under Creative Commons license. Read theoriginal article.

Image credit: / ali awaiss

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