The Burning Question: The Detrimental Effects of Extreme Heat

As global temperatures increase, the adverse effects of extreme heat can be felt in human health, infrastructure, and the environment.

Reading Time: 5 minutes

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By Vicky He

If you felt that this summer was exceedingly hot, you’re not wrong. Temperatures all over the world have hit startling heights, with some regularly being in the triple digits. This is due to multiple factors, the most significant being the release of greenhouse gases like carbon dioxide and methane into the atmosphere. These greenhouse gasses trap the sun’s energy, allowing the Earth to reach temperatures warm enough to sustain life. In recent years, however, human activities like burning fossil fuels, deforestation, and unsustainable agriculture have released excess gasses and amplified the greenhouse effect, leading to global warming at an unprecedented rate. In fact, according to NASA’s data, this past July was the hottest ever recorded. This isn’t an isolated incident, either; the past eight years have been the hottest years on average, showing a clear upward trend in global temperature. Though an uptick of a few degrees may not seem like a lot, the truth is that a seemingly small increase in heat can cause a myriad of issues in many aspects of human life.

Extreme heat is defined as a period of high heat and humidity with temperatures over 90 degrees Fahrenheit for two or more days. The human body regulates itself through homeostasis, maintaining a normal temperature of around 98.6 degrees Fahrenheit. When the external environment gets too hot, the body has to work harder to maintain its normal temperature and can potentially become overwhelmed, resulting in an abnormally high body temperature—hyperthermia. The body cannot handle straying even a degree or two from its comfortable temperature range, and overheating can be fatal. Extreme heat causes approximately 1,300 annual deaths in the U.S. alone, making it the most deadly weather-related hazard.

When the body is exposed to high external temperatures, it can usually correct itself through thermoregulation, the process that maintains the balance between heat absorption and dissipation. The body reacts in a number of ways, such as by dilating blood vessels, increasing blood flow to the skin’s surface, and activating sweat glands in order to release heat through sweating and radiation. However, prolonged extreme heat exposure can overwhelm thermoregulation, causing damage to the body. The widening of blood vessels near the skin allows heat to radiate away from the body, but it also diverts blood and oxygen from vital tissues, which can lead to organ damage and failure. Likewise, though sweating is one of the body’s primary mechanisms for cooling, excessive sweating can lead to dehydration and an imbalance of ions like sodium and potassium, which are necessary for muscle and nerve function. Another example of the body’s protective system turning against itself in extreme heat is the innate immune system. Heat stress can activate the inflammatory response, flooding the affected areas with cytokines and chemicals that can start to attack healthy tissues over time. In addition, extreme heat can push important proteins and enzymes out of their limited temperature range, causing them to denature. Combined, these factors can give rise to severe heat-related conditions.

Heat-related illness comes in three major stages: heat cramps, heat exhaustion, and heatstroke. It begins with heat cramps, characterized by muscle cramps or spasms, often in the legs and abdomen. Next is heat exhaustion, which can cause a variety of symptoms, including headaches, nausea, and lightheadedness. Both of these conditions can be eased by movement to a cooler area, ingestion of liquids, and rest. Conversely, if left untreated, they can lead to the final and most serious stage: heatstroke.

Heatstroke, the most severe heat-related disease, occurs when body temperatures reaches over 103 degrees Fahrenheit. There are two forms: exertional heatstroke, caused by intense physical activity, and the more common non-exertional (classic) heatstroke, which is caused by high external temperatures. The condition is often associated with a lack of sweating because the body becomes so dehydrated that it can no longer cool itself through this method. Other symptoms include seizures, mental impairment, and loss of consciousness. Heatstroke quickly becomes fatal, with symptoms appearing in under 15 minutes and mortality rates as high as 70 percent. Even in cases of survival, heatstroke can cause vital organ damage and neurological dysfunction that persist throughout life. The high body heat may trigger apoptosis, or programmed cell death, in important tissues and neurons. Hyperthermia has been linked to issues with memory and cognitive function. This makes heatstroke and other heat-related illnesses incredibly dangerous but also increasingly common as global temperatures continue to rise.

Another danger of extreme heat is burns, both directly from the sun and from surfaces like metal and pavement. Urban areas are subject to the heat island effect, as man-made infrastructure absorbs heat faster than natural environments, creating “islands” of relatively higher temperature. Over time, this accumulation of heat can lead to surfaces becoming hot enough to burn skin.

Outside of the human body, extreme heat has other adverse effects on artificial constructions. Many of society’s structures are made of concrete. Though this material is known for its durability under environmental stress, concrete is susceptible to temperature changes. As concrete gets hotter, it expands, which can lead to cracking. Asphalt, used in most roads, is also subject to cracking, softening, and deforming when exposed to intense heat. Powerlines, which are usually made of aluminum or copper wiring, can also expand when heated, increasing slack between the lines and causing them to droop. This reduces the efficiency of the lines, and if they sag too low and touch other structures or trees, they can short-circuit, leading to outages. Hotter weather conditions may also encourage people to use more electricity and air conditioners, which not only puts more stress on the power lines but also contributes to the release of greenhouse gasses. Paradoxically, the higher temperatures lead to increased air conditioning use, which in turn creates a positive feedback loop.

Extreme heat conditions also affect the natural environment in harmful ways. High temperatures heat up the oceans and increase the rate of water evaporation. This can lead to more frequent and more extreme hurricanes with greater reach. Previously, hurricanes were confined mostly to the tropics because the waters in other areas were not warm enough to sustain the circulation of heat and spin that a hurricane needs. As global water temperatures increase, hurricanes will be able to form over areas that are usually untouched by such storms, leading to catastrophic flooding and damage to unprepared communities. Increased rates of evaporation can also dry out land and cause droughts, putting affected areas at greater risk for natural disasters like wildfires. Events like the Canadian wildfires that swept pollution and smoke over the East Coast and the more recent Maui wildfires—once uncommon incidents—will become more regular and intense occurrences.

As climate change worsens, the coming summers will only grow hotter and hotter. Meteorologists predict that the summer of 2024 will reach even higher temperatures. If left unchecked, this trend will intensify, continuing the upward crawl toward unbearable heat. By acknowledging the troubling effects of extreme heat and taking action now, we can hope to mitigate the consequences of climate change and maintain livable conditions for years to come.