How Hot is Too Hot?

According to the Guardian UK, July 7, 2021, “More than 5 million people die each year globally because of excessively hot or cold conditions, a 20-year study has found – and heat-related deaths are on the rise… The study involving dozens of scientists around the world found that 9.4% of global deaths each year are attributable to heat or cold exposure, equivalent to 74 extra deaths per 100,000 people.” Even in the United States, air conditioning is not everywhere, and those living below the poverty line face new increasing levels of summer heat that been imposed on them by insufficiently mitigated climate change.

According to a June 19, 2020, report from our CDC, “Deaths attributable to natural heat exposure, although generally considered preventable, represent a continuing public health concern in the United States. During 2004–2018, an average of 702 heat-related deaths occurred in the United States annually... During 2004–2018, a total of 10,527 deaths resulting from exposure to heat-related conditions were identified. Approximately 90% (9,757) of these deaths occurred during May–September.” Heat waves in 2021 and 2022 show temperatures rising even higher.

“The CDC report also noted that “non-Hispanic American Indian/Alaska Natives had the highest rate of heat-related deaths (0.6 per 100,000 population)… Non-Hispanic blacks had the second highest number of heat-related deaths (1,965) and rate ( 0.3 per 100,000 population). Across various levels of urbanization… the highest heat-related mortality rates were observed among persons living in noncore nonmetropolitan (0.3 per 100,000 population) and large central metropolitan counties (0.3 per 100,000 population).”

So an impressive array of academics at Penn State, led by W. Larry Kenney, professor of physiology, kinesiology and human performance and including geographer-climatologists, addressed the question of “When will it get too hot for normal daily activity as we know it, even for young, healthy adults?” There’s no one, fixed number which reflects a clear and absolute dividing line. The health conditions of the people subjected to heat, air movement and importantly, humidity. Their study notes that “Heat waves are becoming supercharged as the climate changes – lasting longer, becoming more frequent and getting just plain hotter…

“Scientists and other observers have become alarmed about the increasing frequency of extreme heat paired with high humidity, measured as “wet-bulb temperature.” During the heat waves that overtook South Asia in May and June 2022, Jacobabad, Pakistan, recorded a maximum wet-bulb temperature of 33.6 C (92.5 F) and Delhi topped that – close to the theorized upper limit of human adaptability to humid heat.

“People often point to a study published in 2010 that estimated that a wet-bulb temperature of 35 C – equal to 95 F at 100% humidity, or 115 F at 50% humidity – would be the upper limit of safety, beyond which the human body can no longer cool itself by evaporating sweat from the surface of the body to maintain a stable body core temperature… It was not until recently that this limit was tested on humans in laboratory settings. The results of these tests show an even greater cause for concern…

“[The] combination of temperature and humidity whereby the person’s core temperature starts to rise is called the ‘critical environmental limit.’ Below those limits, the body is able to maintain a relatively stable core temperature over time. Above those limits, core temperature rises continuously and risk of heat-related illnesses with prolonged exposures is increased.

“When the body overheats, the heart has to work harder to pump blood flow to the skin to dissipate the heat, and when you’re also sweating, that decreases body fluids. In the direst case, prolonged exposure can result in heat stroke, a life-threatening problem that requires immediate and rapid cooling and medical treatment… Our studies on young healthy men and women show that this upper environmental limit is even lower than the theorized 35 C. It’s more like a wet-bulb temperature of 31 C (88 F). That would equal 31 C at 100% humidity or 38 C (100 F) at 60% humidity.” Theconversation.com, July 6th. So how can people copes with extreme heat?

“Staying well hydrated and seeking areas in which to cool down – even for short periods – are important in high heat… While more cities in the United States are expanding cooling centers to help people escape the heat, there will still be many people who will experience these dangerous conditions with no way to cool themselves… Even those with access to air conditioning might not turn it on because of the high cost of energy – a common occurrence in Phoenix, Arizona – or because of large-scale power outages during heat waves or wildfires, as is becoming more common in the western U.S.

“A recent study focusing on heat stress in Africa found that future climates will not be conducive to the use of even low-cost cooling systems such as ‘swamp coolers’ as the tropical and coastal parts of Africa become more humid. These devices, which require far less energy than air conditioners, use a fan to recirculate the air across a cool, wet pad to lower the air temperature, but they become ineffective at high wet-bulb temperatures above 21 C (70 F).” theconversation.com

As our power-generating infrastructure becomes increasingly taxed – representing a push-pull in the battle against greenhouse emissions – a power outage can kill. Cities and states are appointing “chief heat/climate officers” to monitor conditions, offer cooling (and warming in winter) stations where necessary, and helping local areas to plant shade trees, use lighter colors on rooftops to deflect heat and even requiring landlords to provide air conditioning even to impoverished tenants. For all those “I do not want to pay taxes” conservatives who simply state that the richest country on earth cannot afford to contain climate change, I know that they understand the real costs to all of us. You don’t even need advanced mathematical modeling to understand the trillions of dollars climate change is costing us. Grade school arithmetic is enough.

I’m Peter Dekom, and as mother nature is snarling at our arrogance and making us pay for our denial, the message is abundantly clear: “time’s up!”