Extreme heat is dangerous to human health and this is evident from recent heat wave events across the world, including the U.S. There have been reports of record-shattering heat levels. However, experts think that we have yet to see the worst outcomes of rising temperatures.
Man Cooling Down
Heatwave events this summer are giving us a hint of what the future could hold if something is not done about global warming urgently. There have been reports of work interruptions and even fatalities in cities around the world, including in the U.S.
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Research already suggests that extreme heat kills more people than other natural disasters. It appears, however, that the worst is yet to come.
What is extreme heat?
The Centers for Disease Control and Prevention (CDC) defines extreme heat as summertime temperatures that are higher or more humid than normal. It is often described as a period of temperatures in excess of 90 degrees Fahrenheit.
While heat coping ability differs, a 2010 research showed that a wet-bulb temperature of about 95 degrees Fahrenheit or higher qualifies as extreme heat. Such a high temperature makes it hard for the human body to exhaust metabolic heat. This implies that chances of survival drop drastically beyond that level to as low as a few hours.
Putting that in perspective, researchers say most places on the globe do not see wet-bulb temperatures beyond about 86 degrees Fahrenheit.
Wet-bulb temperature takes into account not just heat but also humidity. It is the lowest temperature to which the cooling of air is possible through water evaporation at a constant pressure.
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A high wet bulb can be seen in a place that is highly humid and has a low temperature. It can also occur in a dry place with a very high temperature.
According to an op-ed provided by the University of New South Wales, global warming is on the way to pushing heat waves beyond the 95-degree limit in many places.
Is there a single limit?
As heat tolerance differs, a single temperature reading will not affect everyone the same way. Evidence hints that extreme heat may not be as high as 95 degrees for many people.
In a 2022 study, researchers found that the upper heat limit for their young, healthy subjects was lower than the theoretical limit. These subjects started to show symptoms of hyperthermia (abnormally high body temperature) at about 90 degrees wet bulb.
This somewhat overrules the belief by some that the human body could adjust to increases in heat levels.
Experts say global warming is more to blame for more intense heat waves that are occurring in different places than other factors such as drought or flood.
It is believed that the Earth’s average surface temperature is currently at its highest since records started. The level is also possibly the highest before the last Ice Age.
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Unless something urgent is done, increasing heat looks set to force changes in how we live and work. For instance, summertime routines will have to change and workers may require more breaks from work.
Scientists at the University of Sydney are carrying out exposure studies that are similar to those conducted in the U.S. These will help to know more about how extreme heat can affect human physiology. The researchers are also looking to develop a heat warning system.
What is clear at the moment is that the world needs to attain net zero carbon emissions soonest. Experts expect global warming and associated heat waves to continue until at least that goal is achieved.
References
Sherwood, S. C., & Huber, M. (2010). An adaptability limit to climate change due to heat stress. Proceedings of the National Academy of Sciences, 107(21), 9552-9555. https://doi.org/10.1073/pnas.0913352107
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