Staff Correspondent
Bangladesh has experienced an increase in average temperature by 0.13°C and humidity by 0.3% per decade during 1961–2020, resulting in a rapid increase in human discomfort.
A just released study that assessed the changes in human discomfort in Bangladesh due to temperature and humidity found a three-fold increase in the number of days Dhaka residents feel severe discomfort compared to six decades ago.
During the 1961-1970 period, people living in Dhaka used to experience severe stress outdoors for nine days a year. However, that number of discomfort days tripled to over 29 days a year between 2011 and 2020.
The current issue of the international journal Urban Climate, published by Elsevier, the world’s leading scientific publisher, carried the study results titled – “Changes in human heat discomfort and its drivers in Bangladesh”.
A group of climatologists and experts who undertook the research taking last 60 years’ climate data from Bangladesh, expressed a sense of urgency, stating: “Bangladesh needs to implement the necessary adaptation measures to reduce human heat discomfort. People may be warned about the risks of heat stress and advised on how to avoid it via public awareness programmes.”
Daily climate data from 17 stations distributed across Bangladesh were analyzed in this study to assess the changes in levels of human comfort in the last 60 years (1961–2020).
Talking to Dhaka Tribune on Tuesday, one of the authors of the study paper, Dr Mohammad Kamruzzaman, said: “We can well presume that the number of days when people feel serious discomfort must have further increased over the past three-four years.”
He said Bangladesh needs to implement a heat health warning system to help prepare its citizens for the potentially harmful effects of prolonged exposure to high temperatures.
Additionally, measures must be taken to increase the number of parks and forests, the number of trees, and the use of reflecting materials on buildings to reduce heat stress, Dr Kamruzzaman and his co-authors emphasized.
The researchers used several indices i.e. Heat Discomfort Index (DI), Humidex (HD) etc to see how people in Bangladesh have increasingly been experiencing a higher number of days of discomfort year-round and during pre-monsoon (March, April and May) in particular, over the past six decades.
DI is calculated by using air temperature and relative humidity data while HD, an index number, is used to describe how hot the weather feels to the average person, by combining the effect of heat and humidity.
Rapid surge in heat-induced human discomfort
A reading between 21 and 24 in DI (heat discomfort index) indicates – “50% of the population feels discomfort”, while a reading of 27-29 means – most of the people feel discomfort and 29-32 means – everyone is in discomfort. DI reading above 32 warrants a “state of medical emergency.”
On the other hand, an HD (humidex) reading of 30-39 means, “Some Discomfort” while a reading of 40-44 signifies “Great Discomfort”, 45-54 means situation is “Dangerous” and above 55 is “Very Dangerous.”
The study results showed there has been an increase in severe and dangerous DI days and a decrease in comfort days over the past 60 years.
This indicates an increase in days when all or most people feel severe stress with a decrease in comfort days. The increase in stress days and decrease in comfort days were prominent in some major cities of Bangladesh, including Dhaka, the capital city of Bangladesh.
The researchers said Dhaka is the home of nearly 14% of the country’s total population and is ranked as the sixth most populated city globally and their study finds that the increases in severe or dangerous thermal stress days were nearly three times in the densely populated city of Dhaka and 12 times in Sylhet over the decades.
A large increase in severe DI days was noticed in other major cities. It increased nearly two-fold in Chittagong and three-fold in Rajshahi.
The highest increase in severe and dangerous DI days was in Sylhet city, located northeast of the country. Severe DI days increased from less than two days a year during the 1961-1970 period to over 24 days a year during the 2011–2020 period.
Dhaka experienced an increase in dangerous humid days from 6.9 days a year (1961–1970) to 20.9 days a year (2011–2020).
Similarly, a two-fold increase in dangerous humid days in Chittagong and a 3.5-times increase in Rajshahi was noticed. The highest increase was noticed in Sylhet. Dangerous humid days increased from 1.4 days/year to 19.8 days/year or nearly 14 times.
Asked what propelled such a high increase in Sylhet, Dr Kamruzzaman said it demands further intense study, but noted that its geographical location in a high humid zone and tremor belts might have some correlation.
