A heat wave phenomenon is currently on the rise, in both frequency and lethality, in India and many other countries around the world. Heat waves are caused by high atmospheric pressure systems that compress and heat up the air while decreasing cloud cover simultaneously. Without clouds above, sunlight directly strikes the ground below, removing moisture that would otherwise aid in cooling the air. Over the course of several days, as the pressure increases and the sun heats up the ground even more, heat accumulates, sometimes to a lethal level. A heat wave is most commonly classified as an extended period of time, typically a week or more when temperatures continually exceed the 90th percentile of the local average temperature of a certain area at that particular instance.
A common metric used to measure the severity of a heat wave and its effect on human health is the “wet-bulb” temperature, which accounts for both temperature and humidity. The basic principle is that as humidity increases, the wet bulb temperature is higher than the air temperature, because of a lack of evaporative cooling. Essentially, it is a measure of how fast a person can cool down by sweating.
Just a few hours of exposure to wet-bulb temperatures of 35°C can be deadly for humans. For people doing physical labor, the threshold for humid heat is even lower, at just about 31°C.
Source: Washington Post
In India, the build-up to the monsoon, around mid-June is the most dangerous period of time. With both heat and humidity at deadly levels, the wet-bulb temperatures get perilously close to the 35°C threshold. In South Asia, the regularity of days when wet bulb temperatures get this high has doubled since 1979. In India alone, the total number of heatwave days in 2022 exceeds the total heatwave days in the preceding three years.
Source: Times of India
Although most concerns over heat waves focus largely on the impacts on human health, there is significant economic fallout as well. And these devastating health and financial effects are most often experienced by the most vulnerable populations. The worst affected areas are in South Asia, consisting of billions of people, most of whom lack access to air conditioning. The most deadly effects are felt by low-income labor workers who are often forced to work in these lethal conditions outdoors, people who depend on income from daily work and cannot afford to stay indoors during a heatwave, or households who cannot afford cooling, shelter, or adequate water. Even households with access to air conditioning or coolers have to manage their use in between power outages or high energy prices. Many poor farmers reliant on rain for crop irrigation have seen a significant reduction in rainfall and scorched fields during these heat waves.
These countries of the global south experience the most devastating effects of climate change, yet contribute the least to it. “India accounts for just 3.7% of historic emissions, a smaller tonnage of carbon dioxide than Germany. Pakistan’s burden is just 0.36% of the total, less than Belgium” (Fickling). Often the countries that do contribute the most to climate change experience the least of these devastating effects, and do not realize the realities of climate change as experienced by millions of vulnerable people in the global south.
If urgent action isn’t taken to reduce and terminate activities that are contributing to climate change, the frequency and intensity of these deadly environmental phenomena will continue to increase. According to a 2018 study, “[by] the second half of this century, swaths of the tropics and sub-tropics could be seeing months at a time above the highest recorded wet-bulb temperatures” (Fickling). Currently, heat deaths in India are estimated to be around 89,000 deaths
annually. “With 4C of global warming, heat deaths will rise to 1.5 million a year” (Fickling). Without commitments from and action taken by the global north, in efforts to bear their fair share of the costs of climate change, these conditions will only continue to get worse.
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