why the region should prepare for even more extreme heat in the near future

An extreme heat wave in India and Pakistan has left more than a billion people in one of the most densely populated parts of the world facing temperatures well above 40℃. Although this has not broken historical records for the regions, the hottest part of the year is yet to come.

Although the heat wave is already testing people’s ability to survive and has caused crop failures and power outages, the really scary thing is that it could be worse: depending on what has happened elsewhere, at some point India “owes” even more intense weather. heat wave

Together with some other climate scientists, we recently looked at the most extreme heat waves globally in the last 60 years, based on the largest difference in expected temperature variability in that area, rather than just the maximum heat. India and Pakistan do not figure in our results, now published in the journal Science Advances. Despite regularly having extremely high temperatures and heat stress levels in absolute terms, when defined in terms of deviation from local normals, the heat waves in India and Pakistan to date have not been that extreme.

In fact, we single out India as a region with a particularly low historical tail. In the data we evaluated, we found no heat waves in India or Pakistan outside of three standard deviations from the mean, when statistically such an event would be expected once every 30 years or so. The most severe heat wave we identified, in Southeast Asia in 1998, was five standard deviations from the mean. An equivalent atypical heat wave in India today would mean temperatures of over 50℃ across large swathes of the country; such temperatures have only been seen at localized points so far.

Therefore, our work suggests that India may experience even more extreme heat. Assuming that the statistical distribution of daily maximum temperatures is basically the same around the world, it is statistically likely that an unprecedented heat wave will hit India at some point. The region has not yet had reason to adapt to such temperatures, so it may be particularly vulnerable.

crops and health

Although the current heat wave has not broken any historical records, it is still exceptional. Many parts of India have experienced the hottest April on record. Such heat so early in the year will have a devastating impact on crops in a region where many depend on the wheat crop for both food and livelihood. Usually, extreme heat in this area is closely followed by cooling monsoons, but that’s still months away.

The man carries the unit of the air cooler
Climate adaptation: Air coolers for sale in New Delhi, where temperatures reached 43°C.
Rajat Gupta/EPA

It’s not just crop yields that will be hit the hardest, as heat waves affect infrastructure, ecosystems, and human health. The impacts on human health are complex, with both meteorological factors (how hot and humid it is) and socioeconomic factors (how people live and how well they are able to adapt) coming into play. We know that heat stress can lead to long-term health problems, such as cardiovascular disease, kidney failure, shortness of breath, and liver failure, although we will not be able to know exactly how many people will die in this heat wave due to a lack of necessary resources. health data from India and Pakistan.

what the future holds

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

world map with some countries shaded in yellow
The critical points of population increase over the next 50 years (red circles) all coincide with places where there are no daily mortality data (yellow).
Mitchell, Nature Climate Change (2021), CC BY-SA

In our new study, we investigate how extremes are projected to increase in the future. We used a large set of climate model simulations, which gave us much more data than is available for the real world. We find that the statistical distribution of extremes, relative to a change in the underlying climate, as it generally gets warmer, does not change. In climate models, daily extreme temperatures increase at the same rate as the change in mean climate. The latest IPCC report indicated that heat waves will become more intense and frequent in South Asia this century. Our results support this.

The current heat wave is affecting more than 1.5 billion people, and over the next 50 years, the population of the Indian subcontinent is projected to increase by a further 30%. That means hundreds of millions more people will be born in a region likely to experience more frequent and severe heat waves. With even greater numbers of people set to be affected by even greater heat extremes in the future, action to adapt to climate change must be accelerated, urgently.

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