“The day is hot, the Capels are abroad,
And if we meet we shall not ’scape a brawl,
For now, these hot days, is the mad blood stirring.”
That’s from Act 3, Scene 1 of William Shakespeare’s Romeo and Juliet, where Romeo’s cousin Benvolio says the heat makes people’s “mad blood” stir, causing them to lose their senses and become more likely to fight. Shakespeare set Romeo and Juliet during a hot summer in Verona, with references to the heat contributing to the characters’ short tempers and passionate behaviours.
Verona had suffered probably its hottest summer in 1540, which resulted in the infamous European drought, memories of which were perhaps fresh when Shakespeare wrote his immortal lines. A little more than four centuries later, in 2003, Verona was hit by a heatwave and saw the hottest summer recorded since at least 1540. According to official estimates, the 2003 heatwave caused about 20,000 deaths in Italy alone and more than 70,000 deaths across Europe.
Heatwaves, periods of abnormally high temperatures lasting days to weeks, have occurred throughout human history, but their documentation and understanding have evolved over time. One of the earliest well-recorded events was the 1896 Eastern North America heatwave, which claimed over 1,500 lives in New York City alone. This was one of the events that highlighted the vulnerability of urban areas to extreme heat, a lesson that remains relevant today.
The 20th century saw several significant heatwaves, including the 1936 North American heatwave, which coincided with the Great Depression and the so-called Dust Bowl era (dust storms that damaged crops and fields) that caused widespread drought and over 5,000 deaths. As the century progressed, events like the 1976 United Kingdom heatwave and the 1995 Chicago heatwave brought increased attention to the phenomenon of urban heat islands and the need for city-specific heat management strategies.
Heatwaves have been a recurring challenge in both Africa and Latin America too, with their frequency and intensity increasing in recent decades due to climate change. South Africa faced a significant heatwave in 2015-16, contributing to its worst drought in 30 years. A year before that, Brazil’s southeast region, including São Paulo, suffered from intense heat and drought, leading to water shortages, deaths, and crop losses. The Caribbean islands have also seen an increase in heatwave frequency since the 1980s, with a particularly severe event in 2015 affecting multiple nations.
Back home, Asia has experienced numerous severe heatwaves, with their frequency and intensity increasing in recent decades. In 1998, a significant heatwave hit much of Southeast and East Asia, causing thousands of deaths. In 2018, Japan declared its heatwave a natural disaster after temperatures reached 41.1°C (106°F), causing 65 deaths in a week. Pakistan experienced one of the world’s deadliest heatwaves in 2015, with temperatures in Karachi soaring to 49°C, leading to over 1,200 deaths. More recently, in 2021, several Asian countries including Iraq, Iran, and Kuwait recorded temperatures exceeding 50°C. India has seen several deadly heatwaves, with 2015 resulting in over 2,500 fatalities. Just a few months ago, a massive heatwave in India damaged crops and lives across the country, especially in North India.
The impacts of heatwaves are far-reaching and multifaceted. From a health perspective, extreme heat can lead to a range of illnesses, from heat exhaustion and heat stroke to exacerbation of pre-existing conditions like cardiovascular and respiratory diseases. The World Health Organization estimates that between 1998 and 2017, more than 1,66,000 people died due to heatwaves.
Environmentally, heatwaves contribute to drought conditions, increase wildfire risk, and disrupt ecosystems. The 2021 Western North America heatwave, for instance, is believed to have killed over a billion marine animals along the Pacific coast.
Heatwaves also place immense strain on infrastructure. Power grids can be overwhelmed by increased air conditioning use, leading to blackouts. Transportation systems suffer as roads buckle and railway lines warp under extreme temperatures.
And that takes us to the next crucial point. While heatwaves affect entire regions, their impact is not felt equally. Vulnerable communities, particularly the urban poor, are often hit hardest. The urban heat island effect, where cities experience higher temperatures than surrounding areas due to heat-absorbing surfaces and lack of vegetation, disproportionately affects low-income neighbourhoods with less green space.
Elderly individuals and those with pre-existing health conditions are at higher risk of heat-related illnesses. Outdoor workers, who often come from lower socioeconomic backgrounds, face direct exposure to extreme temperatures.
In developing countries, limited resources for adaptation measures like air conditioning and robust healthcare systems exacerbate the impact of heatwaves. The 2015 heatwave in India, which killed over 2,500 people, predominantly affected the poor and homeless. The economic toll of heatwaves is substantial and multi-faceted. In agriculture, extreme heat can devastate crops and livestock, threatening food security and livelihoods. The 2010 Russian heatwave, for example, caused an estimated $15 billion in economic losses, primarily due to reduced crop yields.
Labour productivity also suffers during heatwaves. A 2021 study published in The Lancet estimated that extreme heat causes global economic losses of $669 billion annually. Outdoor workers are particularly affected, with productivity dropping sharply as temperatures rise. Energy costs surge during heatwaves as air-conditioning use spikes. This not only strains household budgets but can also lead to rolling blackouts, further impacting economic activity. The healthcare costs associated with heat-related illnesses add another economic burden. A 2020 study found heat-related illnesses cost the U.S. healthcare system about $1 billion every year from 2016 to 2020.
Climate models project that heatwaves will become more frequent and severe in the coming decades. The Intergovernmental Panel on Climate Change warns that even if global temperature rise is limited to 1.5°C above pre-industrial levels, 14 per cent of the world’s population will be exposed to severe heatwaves at least once every five years.
So, what do we do?
It starts with a simple exercise: acknowledging climate change is a real and present danger and we need to fight it with sustainable measures. Adapting to a hotter future requires a multi-pronged approach. Urban planning strategies, such as increasing green spaces and using heat-reflective materials, can help mitigate the urban heat island effect. Improved early warning systems and public health measures are crucial for reducing heat-related deaths. Reducing greenhouse gas emissions remains the most effective long-term strategy for limiting the intensity of future heatwaves. This requires international cooperation and a transition to cleaner energy sources.
And that’s a big ask. If anything, the latest heatwave is clear about one fact: it’s time we sat up and took note of this phenomenon and changed track. And that’s why Frontline has joined the debate on extreme climatic events and their unprecedented recurrence, especially in India. Our latest cover takes a deep dive into the heatwave phenomenon. As Divya Gandhi says in her lead essay,India’s record heatwave vows to return: Can we survive the next?
Can we? What do you think?
How did you manage this season’s heat? Read the stories and write back to us with your comments, as always.
For Frontline,
Jinoy Jose P.
We hope you’ve been enjoying our newsletters featuring a selection of articles that we believe will be of interest to a cross-section of our readers. Tell us if you like what you read. And also, what you don’t like! Mail us at frontline@thehindu.co.in
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