Ajit Karn
India, which is on track to become the world’s most populous nation, risks approaching the limit of human survival as its heat waves become more intense and frequent.
After India experienced its warmest February since 1901, the national meteorological office has forecast rising temperatures in the future weeks. This has increased fears of a repeat of last year’s record-breaking heat wave, which caused widespread agricultural damage and led to hours-long outages. While temperatures as high as 50 degrees Celsius (122 degrees Fahrenheit) are intolerable in any circumstance, the harm is exacerbated for India’s 1.4 billion urban residents who lack access to well-ventilated housing or air conditioning.
“Heat stress for humans is a combination of temperature and humidity,” said Kieran Hunt, a climate scientist from the University of Reading who has studied the weather patterns of the country. “India is typically more humid than similarly warm regions such as the Sahara. This means that perspiration is either ineffective or inefficient.”
This is why, in India, the wet-bulb reading, which incorporates air temperature and relative humidity, is a more accurate indicator of thermal duress on the human body. The World Bank warned in a November report that India could become one of the first places in the world where wet-bulb temperatures exceed the survivability threshold of 35 degrees Celsius. Abhas Jha, one of the report’s authors, asked, “Have we become accustomed to heat-induced suffering?” Because it is not a catastrophe with an abrupt onset and has a slow onset, we do not resist it.
While no country is immune to global warming, India stands out for a variety of reasons. The interview with Mr. Hunt that follows has been condensed and edited for length and clarity.
What climate science explains India’s increasingly intense heat waves?
It is helpful to divide heat wave temperatures into two components: the background, or the monthly average temperature, and the anomaly, or the portion added or subtracted by the weather at the time. Since the pre-industrial era, the atmospheric temperature over India has increased by about 1.5 degrees Celsius. Consequently, assuming all other factors remain constant, heat wave weather patterns today would be associated with temperatures approximately 1.5 degrees Celsius higher than if they had occurred a century ago. In certain cities, the urban heat island effect has added approximately 2 degrees Celsius to the baseline temperature. Deforestation contributes as well.
Why are they occurring more often?
This may also be divided into two sections. First, the Indian government’s definition of a heat wave is fixed, so as background temperatures rise, fewer and fewer anomalies are required to surpass the threshold for a heat wave. Secondly, it appears that the weather patterns associated with these anomalies – high pressure over northern India leading to arid, sunny, windless conditions – are also increasing in frequency.
What makes them more threatening?
When temperatures remain elevated for an extended period of time, heat waves that are more intense and hotter tend to cause more fatalities. This is exacerbated by India’s accelerated population growth over the past several decades.
The fact that India’s ambient temperature is already so elevated poses a threat. In May, for instance, the only places on Earth with temperatures comparable to north India are the Sahara and portions of the interior Arabian peninsula, both of which are sparsely populated. With background temperatures already exceeding 40 degrees Celsius, even modest increases are likely to threaten human survival.
How do heat surges affect individuals?
There are far-reaching consequences for Indian society. Extensive heat surges cause significant soil dehydration across vast regions. In addition to the apparent agricultural repercussions, this can delay the onset of the monsoon by a month, which can have a negative impact on agriculture, water security, and even cause localized flooding if heavy rain falls on dry soil that is unable to assimilate it.
Additionally, unusually hot pre-monsoon periods are associated with decreased labor productivity, especially in outdoor sectors such as agriculture and construction; increased demand for cooling, which can strain the power grid and lead to increased greenhouse gas emissions; and general health risks, such as heatstroke, which disproportionately affect children, the elderly, and low-income communities.
Then, how can the damage be mitigated?
On the policy level, implementing urban planning guidelines that prioritize green spaces, shelter, and ventilation in building design is a common topic of discussion in this context. These are gaining popularity in numerous Mediterranean communities. Invest in the research and development of low-energy cooling solutions, such as passive cooling systems, and encourage energy-efficient building design at the corporate level. Encourage the use of cool roofs, green roofs, and tree cultivation in communities to mitigate the urban heat island effect.
Also read: The bizarre rules of the Bengaluru Housing Society have the Internet fuming
What does the future hold for India as the planet continues to warm?
Currently, India rarely exceeds [a wet-bulb temperature of] 32 degrees Celsius, so we require a substantial amount of warming to reach the survivability limit. Nonetheless, as urbanization, and consequently the urban heat island effect, and global warming continue to increase, so do the risks of deadly heatwaves.
