Climate change led to 1000 hours of Extreme Temperature in Delhi and Kolkata

The monsoon season has come to an end, and as we enter October, numerous cities are still experiencing weather conditions reminiscent of hot summers. Once again, this year has provided clear evidence of the impact of climate change, with temperatures on the rise. According to the most recent study, two major Indian cities, Delhi and Kolkata, have collectively endured 1000 hours of heatwaves, with temperatures exceeding the pre-industrial era's average by 4 degrees Celsius.

Interdisciplinary research from the Penn State College of Health and Human Development, Purdue University College of Sciences and Purdue Institute for a Sustainable Future has revealed the above fact. Not only this, if if global temperatures increase by 1 degree Celsius (C) or more than current levels, each year more that a billion people will be exposed to heat waves where they will be unable to naturally cool themselves.

Heat and humidity levels surpassing human tolerance limits

In 2015, 196 nations signed the Paris Agreement which aims to limit worldwide temperature increases to 1.5 C above pre-industrial levels. But the way the rising temperature is showing its local effects, it seems things will worsen in the next 50 years.

Here to study the impact, the research team conducted modeling on global temperature rises, exploring a range from 1.5°C to 4°C. This range represents the worst-case scenario where warming would start to accelerate. The objective was to pinpoint regions on Earth where such warming would result in heat and humidity levels surpassing human tolerance limits.

Northern India experiencing high-temperature

The outcome for almost all the countries including India was horrible. To study the temperature in India, the research team considered the data collected from Delhi, Mumbai, Kolkata and Chennai. According to the data collected, Delhi witnessed 16 hours of temperature 1.5 degree above normal. 39 hours were 2 degrees hotter and 170 degrees had temperatures 3 degree above the pre-industrial era. And 556 hours of Delhi were exposed to the temperature 4 degree Celsius above the pre-industrial era. Similarly, Kolkata witnessed 10, 31 157 and 548 hours respectively.

The study's findings suggest that with a global temperature rise of 2°C above pre-industrial levels, numerous regions will be affected. Specifically, the Indus River Valley, home to 2.2 billion people in Pakistan and India, the eastern part of China with one billion residents, and sub-Saharan Africa with 800 million inhabitants will annually endure prolonged periods of heat exceeding human tolerance.

Heatwaves pose greater risks

In these areas, the predominant type of heatwaves would be characterized by elevated humidity levels. Heatwaves with increased humidity pose greater risks, as the air's limited capacity to absorb excess moisture restricts the evaporation of sweat from human bodies and moisture from certain infrastructure, such as evaporative coolers.

Concerningly, researchers have pointed out that these regions are predominantly situated in lower-to-middle-income nations, potentially leaving a significant portion of the affected population without access to air conditioning or any effective means to alleviate the adverse health impacts of extreme heat. If global warming proceeds to reach 3°C above pre-industrial levels, the researchers have determined that heat and humidity levels exceeding human tolerance will become a reality.

What experts say

Daniel Vecellio, a bioclimatologist who completed a postdoctoral fellowship at Penn State with Kenney said that models like these are good at predicting trends, but they do not predict specific events like the 2021 heatwave in Oregon that killed more than 700 people or London reaching 40 C last summer.

Irrespective of the extent of planetary warming, the researchers emphasized the importance of ongoing concern regarding extreme heat and humidity. This concern should persist even when these conditions remain below the established human tolerance thresholds. In preliminary studies involving older populations, Kenney discovered that older adults are susceptible to heat stress and its related health effects at lower levels of heat and humidity compared to younger individuals.