India’s Renewable Transition in Race Against Heat Impacts

May 6, 2022

Above, CEO of major Indian energy company JSW on energy transition across India, Renewable assessment starts at 2:50. (90 percent of additions last year were renewable)

Meanwhile, India and Pakistan are some of the most vulnerable countries to climate extremes.

Jeff Masters at Yale Climate Connections:

A brutal, record-intensity heat wave that has engulfed much of India and Pakistan since March eased somewhat this week, but is poised to roar back in the coming week with inferno-like temperatures of up to 50 degrees Celsius (122°F). The heat, when combined with high levels of humidity – especially near the coast and along the Indus River Valley – will produce dangerously high levels of heat stress that will approach or exceed the limit of survivability for people outdoors for an extended period.

The latest forecasts from the GFS and European models predict an unusually strong region of high pressure intensifying over southern Asia in the coming week, bringing increasing heat that will peak on May 11-12, with highs near 50 degrees Celsius (122°F) near the India/Pakistan border. May is typically the region’s hottest month, and significant relief from the heat wave may not occur until the cooling rains of the Southwest Monsoon arrive in June. But tropical cyclones are also common in May in the northern Indian Ocean, and a landfalling storm could potentially bring relief from the heat wave.

More from Jeff Masters:

While the heat index – which measures heat stress due to high temperatures combined with high humidity – is often used to quantify dangerous heat, a more precise measure of heat stress is the wet-bulb temperature, which can be measured by putting a wet cloth around the bulb of a thermometer and then blowing air across the cloth. The wet-bulb temperature increases with increasing temperature and humidity and is a measure of “mugginess.” 

Since human skin temperature averages close to 35 degrees Celsius (95°F), wet-bulb temperatures above that critical value prevent all people from dispelling internal heat, leading to fatal consequences within six hours, even for healthy people in well-ventilated conditions. The U.S. National Weather Service defines the “Danger” threshold for wet-bulb at 24.6 degrees Celsius (76.3°F), and “Extreme Danger” at 29.1 degrees Celsius (84.4°F), assuming a 45% relative humidity. 

However, experiments show that a wet-bulb temperature considerably lower—near 31 degrees Celsius (88°F)—is likely fatal for young, healthy people. A 2022 study, Evaluating the 35°C wet-bulb temperature adaptability threshold for young, healthy subjects, had participants swallow a tiny radio telemetry device encased in a capsule that measured their core temperature while performing tasks mimicking basic activities of daily life, until they could no longer maintain their core temperature without overheating. The experiment found that young, healthy adults could not survive extended exposure to wet-bulb temperatures of 30-31 degrees Celsius (86-88°F) in humid environments, and 25-28 degrees Celsius (77-82°F) in hotter, dryer environments (see the paper’s press release, and Figure 2). For older people, and those with health conditions, the critical wet-bulb temperature is likely even lower.

Eureka Alert – AAAS:

It has been widely believed that a 35°C wet-bulb temperature (equal to 95°F at 100 percent humidity or 115°F at 50 percent humidity) was the maximum a human could endure before they could no longer adequately regulate their body temperature, potentially causing heat stroke or death over a prolonged exposure.

Wet-bulb temperature is read by a thermometer with a wet wick over its bulb and is affected by humidity and air movement. It represents a humid temperature at which the air is saturated and holds as much moisture as it can in the form of water vapor, and that a person’s sweat will not evaporate at that skin temperature.

But in their new study, the researchers found that the actual maximum wet-bulb temperature is lower – about 31°C wet-bulb or 87°F at 100 percent humidity – even for young, healthy subjects. The temperature for older populations, who are more vulnerable to heat, is likely even lower.

W. Larry Kenney, professor of physiology and kinesiology and Marie Underhill Noll Chair in Human Performance, said the results could help people better plan for extreme heat events, which are occurring more frequently as the world warms.

“If we know what those upper temperature and humidity limits are, we can better prepare people – especially those who are more vulnerable – ahead of a heat wave,” Kenney said. “That could mean prioritizing the sickest people who need care, setting up alerts to go out to a community when a heatwave is coming, or developing a chart that provides guidance for different temperature and humidity ranges.”

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