Climate Change

Heat index is a critical tool to help beat heat stress

Heat index correlates thermoregulation, relative humidity and the air temperature

Heat stress has affected global health and has become an issue of consideration for human well-being. Photo: iStock__

A glass of water after a walk in the hot weather feels like the definition of happiness. But it is also necessary for our body to regulate its temperature when it is sweltering hot. However, humans’ ability to regulate their body temperature is getting affected by severe heat stress, thanks to urbanisation and climate change. 

When the human body gets hot, it begins to perspire and sweating helps it cool. However, the rate of evaporation from our body decreases when temperatures are increased and high humidity or atmospheric moisture is present. 

Read more: Heat-stressed: Europe warming twice as fast as global average, shows new report

A decreased rate of evaporation makes us feel warmer. This condition occurs when the body’s way of controlling its internal temperature starts to fail and leads to heat stress.

The rise in the number of buildings, urbanisation and climate change are directly contributing to an increase in temperature and shifting the heat balance of our planet.  This is leading to severe heat stress by disturbing the ecological system both locally and globally.

The Earth’s average temperature is likely to rise by 1.5 degrees Celsius before 2040, according to a 2021 study by United Nations’ Intergovernmental Panel on Climate Change. An important tool known as the heat index is used to study the factors influencing the overall physiological and psychological disturbances in human beings.

The index is a more accurate measure that correlates thermoregulation, relative humidity and the air temperature. It also lets people know how much heat their bodies can handle before it becomes dangerous.

Heat stress has affected global health and has become an issue of consideration for human well-being. In India, nearly 706 heatwave events were recorded in the past 50 years — a threefold increase in their number. 

It is time to recognise heat stress as a public issue and to raise awareness among the people about how to beat heat stress with our own heat index.

Read more: A device that uses sweat for real time physiology check

Effects of heat stress 

Thermal discomfort affects a variety of activities and jobs. Workers have to deal with  extreme heat stress, which can hurt their work and productivity and even put their lives at risk. Occupational health risks ultimately affect the nation’s income and economy. 

In India, about 75 per cent of workers, which is around 380 million people, experience heat-related stress. The increasing heat intensity poses a substantial risk to human health and life. This extreme heat is a health hazard and has continued to grow as a disease burden over the past few years. 

Human health can be severely affected. It can cause dehydration, acute cerebrovascular accidents and blood clots, which result in cramps, exhaustion, stress, heat stroke and even death in extreme cases

The elderly, children, people with psychiatric disorders and other diseases are particularly impacted. A significant number of deaths have been reported in different parts of the world due to heat vulnerability. 

Read more: The reality of living with 50℃ temperatures in our major cities

IMD’s heat stress index 

The real-feel experimental forecast of the heat index issued by the India Meteorological  Department (IMD) recently ensures the implications and precautionary measures to be taken by the public to overcome the seasonal rise in temperature. 

A heatwave is declared if the maximum temperature crosses 40°C and is 4.5°C above normal for the day. A severe heatwave is declared when the temperature is above 40°C and 6.5°C above normal. 

A heat index will help the central government formulate an appropriate heat management plan, especially as heat conditions are expected to worsen in India under global warming. 

The IMD will release hazard scores in all states on different weather parameters that lead to or aggravate extreme heat, news websites reported in April 2023. These scores are expected to help in heatwave management.

To determine the hazard scores, a graded weightage will be assigned to each  meteorological parameter and aggregate the scores at each weather station.  

The main distinction between India’s heat hazard score and the United States’ heat index is that India will also take into account factors that aggravate heat conditions, such as the minimum temperature, wind and exposure time.

Heat Index of major cities in India

Data: IMD, 2023

Significance of heat index 

It is critical to know the threshold levels of heat stress prevailing in various parts of the country. The importance of the heat index lies in its capacity to assist individuals in  taking the necessary measures to safeguard themselves against the adverse consequences of heat. 

Read more: Indian economy will be hit hard by rising heat: Global report

In addition, it is beneficial in numerous sectors, including agriculture, livestock and wildfire management and other industries, as high temperatures can have notable effects on both the economy and the environment. 

In terms of public safety, it is crucial to forecast potentially harmful heat conditions and take the necessary precautions to avoid heat-related illnesses like heat exhaustion or heatstroke. 

Some areas where heat forecasts are significant are:

  • Water resource management to estimate the demand and allocation of water in reservoirs,  agriculture and drought-prone areas
  • Climate change adaptation strategies.
  • Helping policymakers create precise advisories, warnings, emergency response planning,  cooling centers and outreach. 
  • Awareness among the general public to beat the prevailing heat.

The extended heat index can be mapped onto the physiological responses of an idealised human and can provide an indication of regional health outcomes for varying degrees of global warming. The index can bring awareness about climate change and alerts us to pursue it with the required preparedness. 

Read more: Intensity, extent and duration of severe heat waves to increase dramatically: study

Improving the green cover and necessary actions to mitigate this  change will improve the thermal comfort of living beings.

It will, thereby, improve work  efficiency and encourages people to participate in different activities, which will benefit residents from various perspectives, including physical, environmental, economic, and social aspects,  thereby promoting the quality of life. 

Priyanka B is a PhD Research Scholar at Dr Y S Parmar University of Horticulture and Forestry; Shubham Sharma is a PhD Research Scholar at Dr Y S Parmar University of Horticulture and Forestry and Satish Kumar Bhardwaj is a Professor and Head of Department of Environmental Science at Dr Y S Parmar University of Horticulture and Forestry

Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth

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