The lack of a localised heat stress index for India that takes into account both temperatures and relative humidity was highlighted at the International Conference on Lightning and Extreme Weather Events on December 9, 2024. This comes at a time when high wintertime minimum temperatures are being experienced in many places across the country.
“While heat waves with their temperature thresholds are well defined by the India Meteorological Department (IMD), similar definition for heat stress which combines the impact of temperatures and relative humidity does not exist for India,” Lakshmi Kumar T V, associate professor at the Jawahar Lal Nehru University said at the event where he presented his work on the implications for heat stress in India garnered from global climate models.
High temperatures combined with moisture can be a cause for higher felt temperatures as increased moisture heightens relative humidity which can hamper the human body’s ability to cool itself through perspiration.
Kumar’s research shows that with future warming and increased moisture levels in the atmosphere the coastal areas of the country would be more at risk from heat stress than other areas such as the Indo-Gangetic plains, where heat waves have been a major risk till date.
According to Kumar’s analysis, the cities on the eastern coast of India would be impacted more by temperatures and those on the western coast would be impacted by relative humidity.
Changes in heat stress levels in many Indian coastal cities, especially along the western coast such as Surat and Mumbai, was drastic throughout the daytime hours between 2001 and 2020 as compared to 1981 and 2000, according to Kumar’s research.
Currently, many areas along the western coast of India have been suffering from much higher-than-normal winter temperatures, especially in terms of minimum or nighttime temperatures.
In early December when wintertime moderate temperatures should have set in, Mumbai was clocking minimum temperatures in excess of 25°C, Ratnagiri recorded a minimum temperature of 26.6°C and Goa 26°C, as per M Herrera, weather historian and data analyst.
Mangaluru also broke its minimum temperature record on December 2 with 26°C. Such knowledge of new and compounding risks of extreme weather such as heat stress is lacking in many countries, including in India, said Herrera.
“What we are finding is that risk knowledge is lagging behind some of the other aspects of early warning systems. It is one thing to not understand the risks of today but with climate change, those risks are changing and may not be the risks of tomorrow,” Ko Barrett, deputy secretary general of the World Meteorological Organization told Down To Earth at the recently concluded 29th Conference of Parties to the United Nations Framework Convention on Climate Change in Baku, Azerbaijan.
The Early Warnings for All initiative looks to make countries understand the risks they are facing, have the forecasting warnings in place, have mechanisms to get those warnings out to people, building short-term responses and long-term resilience to disasters as they are unfolding.
“Weather observations from developing countries are essential for long-term global climate modelling. If you have large areas where you have no observations, your models are not being trained fully robust datasets. That is why within the Early Warnings for All initiative, we have placed such an emphasis on addressing these data gaps,” said Barrett.