The recent headlines about the hottest day ever recorded on Earth have been hard to miss. On July 3, global temperatures reached an average of 62.62 F, only to rise again the next day to 62.92 F. While these numbers may seem unremarkable, the extreme heat that accompanied them tells a different story.
In Africa, temperatures soared to 122 F, while Antarctica, in the midst of winter, experienced temperatures of 47.6 F. The Washington Post warned that as many as 54 million Americans were at risk of dangerous heat exposure on July 4 alone. Scientists are now expressing concern that we are entering uncharted territory, and humans may soon reach their limits of adaptability.
Camilo Mora, a professor of data analytics at the University of Hawaii-Manoa, explains that humans have taken millions of years to develop the ability to thermoregulate. As temperatures continue to rise, it will take an equally long time for humans to adapt. Mora and his colleagues have been studying the risk of extreme heat for decades and have found that the planet has warmed by about 1 C in the last decade, resulting in a 2,300% increase in deaths from heat waves.
Heat exposure can have devastating effects on the body. It begins with thermoregulation, where the body tries to cool off through sweating. However, when the body's core temperature becomes too hot, a vicious cycle of multiorgan breakdown and failure occurs. The heart can fail, dehydration can lead to blood clots and stroke, kidney failure may occur, and the lungs can be deprived of oxygen, resulting in respiratory distress. Inflammation can trigger clots that cut off blood supply to vital organs, causing fatal bleeding, and damaged muscle tissue can cause kidney failure.
While most people may associate extreme heat with fatigue or headaches, the reality is that heat exposure can damage vital organs and lead to permanent disability or death. The wet-bulb temperature, which represents the upper limit for human adaptability, is an important factor in determining the risks of extreme heat. If the air is saturated with humidity, evaporation and cooling become impossible, putting individuals at risk.
Perception and risk also play a role in heat-related illnesses. People may not realize the severity of the heat or make proactive decisions to protect themselves. This is particularly true when temperatures exceed 104 F, affecting brain function and rational decision-making.
Certain groups, such as older adults and children, are more vulnerable to extreme heat due to factors like limited mobility or smaller surface-to-body ratios. However, even with certain advantages like genetics, heat acclimation, fitness, or hydration, all humans are ultimately susceptible to the consequences of a warming planet.
The reality is that extreme heat is not just a problem in other parts of the world; it is happening everywhere, and it is happening to us. The implications of this warming trend are concerning, and urgent action is needed to mitigate its effects.