Of global warming and wet bulbs

Recently came across an article that carried an alarming info about the ongoing summer season. It spook/spoke of a scenario called Wet bulb and mentioned that, at present rate, Chennai will become inhabitable for humans by next decade. Made me wonder what is this bulb thing that is going to give bulb to entire Chennai. Apparently, it was a serious matter, needing immediate and prolonged discussion with effective action. 

The wet-bulb temperature is the lowest temperature that can be reached under current ambient conditions by the evaporation of water only. Even heat-adapted people cannot carry out normal outdoor activities past a wet-bulb temperature of 32 °C (90 °F), equivalent to a heat index of 55 °C (130 °F). It is estimated that beyond 35°C, a human body can no longer cool itself through perspiration. India is typically more humid than equivalently hot places, like the Sahara. This means sweating is less efficient, or not efficient at all. This year Delhi’s highest Wet bulb temperature was 33.7 degrees while Chennai went as high as 32.8 degrees. 30 degrees is considered as a safe benchmark and what is frightening is the rapid rate at which threshold’s are getting breached with major Indian cities tottering towards the inhabitable mark. This scenario is not the typical stats and metrics that get bandied about during world environment day or any such targeted commercial events and is a very real and present danger that is fast approaching levels from which there may be no come back. When the wet bulb temperature breaches 35, body loses the ability to cool itself. Internal organs will begin to malfunction and eventually stop functioning.

Once the wet-bulb temperature exceeds 35 degrees Celsius (95 degrees Fahrenheit), no amount of sweating or other adaptive behavior is enough to lower your body to a safe operating temperature. Most of the time it’s not a problem, because the wet-bulb temperature is usually 5-to-10 degrees Celsius below body temperature, even in hot, humid places. Indeed, if humidity is low, extreme temperatures are tolerable. If you’re sitting in the shade with unlimited drinking water in California’s Death Valley, conditions may not be pleasant, but they’re survivable. But in humid regions, once you approach wet-bulb temperatures of 34-to-36 degrees Celsius (93-to-97 degrees Fahrenheit), it doesn’t matter what you’re doing. You can’t survive for extended periods of time. Those most susceptible to high wet-bulb temperatures include the elderly, people who work outside, and those with underlying health issues. People without access to air conditioning are also vulnerable. Air conditioning removes humidity from the air and is the best solution when wet-bulb temperatures get too high. Fans can help sweat evaporate more efficiently, but they’re less effective.

As advised by the National Disaster Management Agency (NDMA) To minimise the impact during the heat wave and to prevent serious ailment or death because of heat stroke, you can take the following measures:

 Avoid going out in the sun, especially between 12.00 noon and 3.00 p.m.

 Drink sufficient water and as often as possible, even if not thirsty

 Wear lightweight, light-coloured, loose, and porous cotton clothes. Use protective goggles, umbrella/hat, shoes or chappals while going out in sun.

 Avoid strenuous activities when the outside temperature is high. Avoid working outside between 12 noon and 3 p.m.

 Avoid alcohol, tea, coffee and carbonated soft drinks, which dehydrates the body.

 Use ORS, homemade drinks like lassi, torani (rice water), lemon water, buttermilk, etc. which helps to re-hydrate the body.

 Use fans, damp clothing and take bath in cold water frequently.