The risk of heatwaves is likely to increase ten times during the twenty-first century with over approximately 70% of India’s land to be influenced by these heat waves covering magnitudes greater than 9.
A heat wave is a prolonged period of excessively hot weather. These prolonged and intense heatwaves have become more frequent and have covered a major part of the globe leading to short-term increase in mortality and posed negative impacts on infrastructure. A climate model suggests that the annual mean temperature of India has risen by 0.85°C from 1901 to 2015 and the surface temperature is also expected to show a substantial increase in the future years.
This increased mean temperature could consequently lead to more intensified heatwaves that are prone to last for longer durations or occur more frequently.
Also, instead of single events taking place across space and time, natural hazards often appear simultaneously. For example, heatwaves and droughts are commonly known to occur together and this in turn could trigger secondary events such as wildfires. In addition, the co-occurrence of droughts and heatwaves can lead to crop losses causing food insecurity. All these together, add to pre-existing vulnerabilities and can amplify inequalities.
Since the last decade that is from 1980-1989 to the present years, there has been 87% rise in the number of climatological and meterological disasters and 40% of the population has been affected.
The IPCC scientists and other climate researchers have predicted that the number of hot days and heatwaves are only going to increase especially near the tropics. There is also a high-confidence prediction that these heatwaves are likely to be widespread in the tropical region with 1.5°C rise in global temperature. A research report showed that if global warming is limited to 1.5°C instead of 2°C, on average 420 million fewer people would be exposed to extreme heatwaves and about 65 million people could be saved from being exposed to exceptional heatwaves.
Although, heatwaves are dangerous for everyone being exposed to them, but population with major risk of adverse impacts include the elderly, pregnant women, lactating mothers and infants.
The older individuals, especially the ones who have pre-disposing health conditions are seen to be more susceptible to heat. Sweating is a very important phenomena and body’s natural way for thermoregulation. With age sensitivity, thermoregulation of skin reduces, which results in less sweating, thus delaying the essential lowering of body temperature.
Another group of population being more prone to heatwaves is pregnant and lactating women and infants. With the increase in temperature, there is an increase in the air pollution which is claimed to be a major reason for stress amplification in both maternal and fetal health. Additionally, a research study showed that with the increase in temperature, pregnant ladies deliver babies at lower gestational age. The report showed that pre-term delivery increased from 1% to 6% with rise for every 2°C. The consequences of these births are resulting in impairment of child’s growth and development and affecting their lifespan.
Preparatory measures and response to heatwaves
The devastating heat waves are taking the lives of several people across the globe. In the wake of this emergency, Ahmedabad's innovative model is preparing a vulnerable population comprising school-going children, street vendors, midday-rush delivery workers, traffic police, elderly people and the outdoor laborers, for rising temperatures. For this Ahmedabad Municipal Corporation (AMC) in collaboration with public health and policy, experts developed a local response for saving lives in extreme heat scenarios.
Home to nearly 8 million people with an annual population growth rate of 2.5%, Ahmedabad is rapidly urbanizing its municipal corporation.
Ahmedabad in the year 2010 witnessed a record-breaking heat wave which led to the death of around 1,344 people. In the year 2013, the city came out with its first heat action plan with an initial warning system for South Asia. Since then, till 2019, the heat action plan has been iterated 6 times.
The plan included the processes that involved the identification of vulnerable populations and the reasons behind their major risks, to develop strategies and their alongside responses as well as activating heat alerts. The plan of action under the supervision of climate experts and local authorities is evaluated and updated annually.
Many scientists argue on the fact that the more necessary step is to take action on mitigating the risk of heatwaves rather than focusing on what temperature determines the count of extremely hot days categorizing into a heat wave. The two most important barriers in disaster risk reduction are data collection and the operational research. Also, heatwaves needs to be operationally defined at every national as well as at state levels that could trigger response or early prevention. As for now there is no clear start or end date of heat wave events for many countries. Thus, it becomes quite difficult to state the “emergency” period of heat wave around which the mortality rate or other impacts could be measured.
However, many promising actions are being adapted by a number of countries to address these issues. For example, in Pakistan, hazard prediction model during heat wave season is used to provide a prior 10-days warning of events in key population centers. In the similar manner, Vietnam Red Cross has brought into implementation a forecast based funding scheme that allows for an immediate action when heat waves continue to be extreme for more than 2-3 days period. These programs not only trigger the release of funds and resources but also help in mitigating the health impact caused due to heat events.
Addressing heatwaves in India
The criterion for declaring heat wave: 40°C for plains, 30°C for hilly regions based on actual maximum temperature
Maximum temperature ≥45°C: Heatwave
Maximum temperature ≥47°C: Severe Heatwave
Based on departure from normal
4°C to 6.4°C: Heatwave
>6.4°C: Severe Heatwave
The Indian Meteorological Department (IMD), in collaboration with The National Disaster Management Authority (NDMA) are working in heat wave prone states (Punjab, Haryana, Delhi, Uttar Pradesh, Bihar, Jharkhand, West Bengal, Odisha, Madhya Pradesh, Rajasthan, Gujarat, parts of Maharashtra & Karnataka, Andhra Pradesh and Telengana. At times Tamil Nadu and Kerela are also affected by these extreme waves) by issuing a heat wave warning 3-5 days in advance and trying to reduce the mortality rate due to these heatwaves. Issuing early warning for these heatwaves could help save more lives and would provide local administrations to take better actions in these extreme situations.
The curve for both the compounding and cascading hazards is anticipated to rise in the coming years, the major reason behind this being climate change. However, these events and their consequences still remain poorly understood. This lack of understanding could thus lead to underestimating the risk, these extreme events bring with them. So, it becomes necessary to have a keen knowledge on the compound and cascading effects of disasters (heatwaves and droughts) for reducing their risk.