Smothered by heatwaves as climate swings

A study shows how the open space on the western bank of the Sabarmati river in Ahmedabad acts as a heat sink. (Image: Emmanuel Dyan, CC BY 2.0)
A study shows how the open space on the western bank of the Sabarmati river in Ahmedabad acts as a heat sink. (Image: Emmanuel Dyan, CC BY 2.0)

In recent times, India has been routinely experiencing abnormally hot days during the summer months of April and May. These deadly heatwaves marked by excessively hot weather along with high humidity are on the rise and are causing a record number of deaths of humans and livestock.  

India recorded a severe heatwave between mid-May to mid-June 2019 when the highest temperature was recorded at Churu, Rajasthan at 50.8°C, a near-record high in India. High temperatures have broken records in various cities across India and in 2019, 11 of the 15 warmest places in the world were all located in the country.

Deadly heatwaves likely in India due to recent Arctic warming

A recent study titled “Large-scale connection to deadly Indian heatwaves” by researchers from India and Brazil shows convincingly that deadly Indian heatwaves occur due to a theoretical mechanism called “Quasi-Resonant Amplification (QRA)”. The research was published in the British journal ‘Quarterly Journal of Royal Meteorology’.

The study has for the first time shown that heatwaves leading to deaths, can occur in India, due to QRA, caused by Arctic warming, a result of global warming. The Arctic region is warming up like never before and at an alarming rate with temperatures increasing more than twice as fast as the global average.

In the QRA mechanism, the so-called planetary Rossby waves amplify by resonance when the free Rossby waves (generated due to rotation of the earth, discovered by C. G. Rossby in 1939) and forced Rossby waves (forced by earth's topography, discovered by Charney and Eliassen in 1949 or heating discovered by Smagorinsky in 1954) coincide in their horizontal scale, called wavelength. This is related to the number of these waves around a latitude circle.

Serious heat stress in south Asia

Another study indicates that deadly heatwaves are likely to be more commonplace in South Asian countries, including India, in the coming decades even if global warming is limited to 1.5°C. The study published in the journal Geophysical Research Letters tries to project the amount of heat stress residents of the region will experience in the future finds with 2°C of warming, and finds that the population's exposure to heat stress will nearly triple.

The study by Fahad Saeed, Carl‐Friedrich Schleussner and Moetasim Ashfaq suggests that this abnormal increase in extreme heat events can lead to potentially repairable but significant economic damages and irreparable losses of human lives. It also creates unsafe labour conditions in major crop-producing parts of India, such as Uttar Pradesh and West Bengal, as well as coastal regions and urban centres like Kolkata, Mumbai, and Hyderabad.

In this study, climate simulations and projections of future population growth were used to estimate the number of people who will experience dangerous levels of heat stress in South Asia at global warming levels of 1.5 and 2°C. The researchers estimated the wet-bulb temperature residents could experience, which is similar to the heat index, as it takes into account both humidity and temperature.

The study noted that a wet-bulb temperature of 32°C is considered to be the point when labour becomes unsafe, and 35°C is the limit to human survivability when the body can no longer cool itself. Based on the analysis, the study suggests that 2°C of warming may increase people’s exposure to unsafe labour temperatures by more than two-fold, and exposure to lethal temperatures by 2.7 times, as compared to recent years.

As per the study “the global mean temperatures are currently rising at an average rate of around 0.2°C per decade (Drancourt & Zingue, 2020; IPCC, 2018), and presently the net increase in temperatures with respect to the pre‐industrial period is around 1°C. With the current trajectory of emissions and pace of warming, it is expected that a 1.5°C warmer world compared to pre‐industrial levels could be reached by 2040 (IPCC, 2018).”

There are some areas in South Asia that are already getting exposed to deadly heat stress conditions and an addition of half a degree to the current global warming levels would further expose a substantially large population to more prevalent deadly hot extremes in many new geographical areas especially in several major urban centres and Indo‐Gangetic Plains.

The study points to serious implications for social‐ecological systems in south Asia that inherently exhibit low adaptive capacity and serve as a wake‐up call for South Asian countries to collaborate in their fight against climate change. There is a need to reduce inequalities and lower population growth associated with scenarios of sustainable socio‐economic development (Andrijevic et al., 2020).

Role of urban bodies

There is a need to learn from examples of how urban bodies have worked on reducing the impacts of extreme and frequent heat waves especially in the light of other stressors such as the pandemic and the effects of Cyclone Tauktae in some coastal states.

Ahmedabad is a case in point. It has developed an extreme heat action plan following the 2010 severe heatwave which was reported to have caused over 1,300 excess deaths. Extreme heat can lead to heat exhaustion and heat stroke and can worsen chronic cardiovascular and respiratory diseases. Vulnerable groups at risk of heat-related health issues include outdoor workers, children, elderly people and poor residents of slum communities.

The heat action plan provides a framework for implementation, coordination and evaluation of extreme heat response activities in the urban area that reduces the negative impact of extreme heat. The plan's primary objective is to alert those populations at risk of heat-related illness in places where extreme heat conditions either exist or are imminent and to take appropriate precautions.

The plan adopted by the Ahmedabad Municipal Council (AMC) as part of its annual disaster preparation plan for the city was centred on enhanced public awareness of extreme heat, an early warning system and heat preparedness planning. This was followed by broad-scale interventions across the city as a result of which in 2015 a heatwave comparable to that of 2010 led to just 7 deaths.

Woman looks at Cool Roofs Billboard in India

Public hoardings on heat stress prevention at Ahmedabad (Image: Natural Resources Defense Council)

A recent webinar organised by the Natural Resources Defense Council, an organisation working on environmental issues discussed that as India faces the second wave of the COVID-19 pandemic multiple strategies can be effective in building resilience to extreme heat. “Long-term resilience is critical to building a public health infrastructure that is robust enough to withstand severe short-term crises such as the current pandemic and persistent climate stressors such as extreme heat.”

Organised in partnership with Climate Trends, Indian Institute of Public Health-Gandhinagar (IIPH-G), Administrative Staff College of India (ASCI), and Mahila Housing SEWA Trust (MHT) the webinar called for the need to have an institutional response to extreme weather events such as heat waves from a public health perspective.

It recommended strategies such as heat action plans, incorporating early and warning systems, preparedness strategies and community outreach, help reduce mortality and enhance community resilience to extreme heat episodes. “Additionally, strategies such as cool roofs, which help keep indoor temperatures low and address the urban heat island challenge, are effective in providing low-cost cooling access.” 

There is a need for cities and states to implement plans on heatwave management similar to that in Ahmedabad by building local infrastructure and governance capacities and putting in place early warning systems.