Maximum and minimum temperatures that we see in weather bulletins do not give the complete picture. Their data are based on conventional dry bulb thermometer readings.
In times of global warming and climate change, wet bulb temperature recordings are more realistic. It tells us how habitable a place is for humans and factors in both heat and humidity. It indicates what heat and humidity means for the human body’s ability to cool itself.
High humidity levels combined with high temperature levels severely impairs the body’s cooling mechanism. Simply put, the body cools itself by sweating. But water will not evaporate from the skin when atmospheric humidity rises beyond a particular level.
A wet bulb temperature of 32-degree Celsius is usually the maximum that a human body can endure and carry out normal outdoor activities. This is equivalent to a dry temperature of 55-degree Celsius.
A wet bulb reading of 35 degrees is life threatening and can cause heat stroke and even death. Reportedly many parts of India already experience the maximum tolerable wet bulb temperature in peak summer. The term wet bulb comes from a way the measurement is taken by wrapping a piece of wet cloth around the end of a thermometer to see how much evaporation can decrease the temperature.
As a result of global warming, water bodies are evaporating at higher rates than before, raising humidity levels in the atmosphere. Wet bulb temperatures will be the new norm in assessing temperature and its impact on the human body.