Threshold of human tolerance against heat
In 2010, a study showed that the human body cannot tolerate humid air temperatures higher than 35 degrees Celsius. But new studies consider this limit to be lower. For example, the tolerance limit for young people is 45°C with 25% humidity. But if the humidity reaches 80%, this limit is reduced to 34 degrees. This limit is even lower for the elderly; So that the temperature of 32.5 degrees Celsius in 80% humidity can be deadly.
The threshold limit for heat tolerance is the point at which the body can no longer dissipate excess heat. In such conditions, the internal temperature of the body increases continuously, which eventually leads to heatstroke and death within a few hours.
Most of us are familiar with temperatures above 34°C, but we tolerate dry heat much better than humid heat. Humid conditions make it very difficult to use the body’s main way of getting rid of heat, which is sweating. We need air to evaporate the sweat from the skin and carry away the heat. But humidity disrupts this process. When the amount of water in the air is higher, it becomes more difficult for sweat to evaporate.
The global threat of humid heat and adaptation constraints
Heat is a silent killer and one of the deadliest climate threats. Unlike disasters such as floods, fires or other climatic events, heat is often invisible and its effects are easily ignored. Heat-related mortality rates are difficult to track and are probably even underestimated. However, statistics show that heat is one of the deadliest climatic disasters in many parts of the world. Until now, much research has focused only on the “air temperature” variable, but recently scientists have begun studying the lesser-known threat of deadly humidity.
Heat is one of the deadliest climatic disasters in many parts of the world
Moisture comes from the evaporation of water from oceans and large water sources. As the oceans warm due to climate change, more moisture is produced. This means that humid heat poses a more serious threat, especially in coastal areas. For this reason, dry Saudi Arabia and other countries of the Arabian Peninsula are particularly at risk; These areas are surrounded by shallow and warming seas.
But the threat is not limited to coastal areas; Moisture is transported inland by a phenomenon known as “atmospheric rivers”, creating conditions similar to periods of deadly humidity in areas such as northern India.
Now the threat of humid heat is increasing dramatically. Currently, deadly humid heat is seen in the Persian Gulf, Bangladesh, northern India and parts of Pakistan and Southeast Asia. People die from these events, but the death rate is not properly recorded. This year’s heat waves closed schools in the Philippines, India and Bangladesh and killed dozens of people during India’s election.
read more
The humid heat will affect not only the developing countries but also the major economies of the world. If there is no rapid reduction in greenhouse gas emissions, this deadly phenomenon may become an annual phenomenon in different parts of the world.
We might think we can adapt to the heat, but adapting to the deadly humidity and heat is severely limited. Although technologies such as air conditioning can be effective in dealing with the heat, the solutions also have their limitations. The widespread use of coolers puts pressure on the power grid and makes the situation more critical with power outages.
The fatal tragedy of Hajj pilgrims dying due to the heat of Mecca is not a fictional story, but a serious warning to the world. Such incidents show that deadly humid heat is no longer just a futuristic threat and is already happening. The only way to prevent similar disasters is to rapidly reduce greenhouse gas emissions and end dependence on fossil fuels.
The research findings have been published in the journal Nature.