The New Thermal Divide - Part 1: Anatomy of an Invisible Killer

The New Thermal Divide - Part 1: Anatomy of an Invisible Killer

Heat arrives silently and operates as an invisible force. It does not bend tree branches or shake the ground to announce its presence. Instead, it surrounds people and works on them in ways they cannot anticipate or control. This type of extreme heat is no longer an incremental bump on the thermometer. It acts as an active, destructive force. This invisible force is the first-order effect of a hotter planet, driving planetary chaos, drought, and wildfires.

The Earth is quickly warming due to the continuous burning of fossil fuels. Global temperatures have risen by 2.2 degrees since the preindustrial era. This warming pushes the global climate out of the Goldilocks Zone, the specific temperature range where life thrives. When temperatures rise too far and too fast beyond this zone, living things die. Understanding this potent, life-altering heat is essential, as it dictates the reality of the growing thermal divide. This division separates the cool from the suffering and the lucky from the damned.

The Arrival of the Heat Dome

In the summer of 2021, the Pacific Northwest received warnings about an impending heat wave. This event was born when atmospheric waves created a high-pressure lid over the Pacific Ocean. This lid trapped heat radiating up from the water, allowing it to gather beneath. Scientists named this phenomenon a heat dome. Land reflects and amplifies heat more efficiently than water, increasing the dome’s intensity as it drifted toward the coast.

The heat surge was sudden and historic. In Portland, the temperature jumped from 76 degrees to 114 degrees in just twenty-four hours, the hottest reading in 147 years of observations. Oregon’s ferny landscape suddenly felt like the hard-baked steel and sand of Dubai. Regionally, emergency management directors opened cooling centers in libraries and churches for homeless populations and vulnerable residents. The Oregon Convention Center provided a cool refuge for hundreds of people in Multnomah County. Officials advised that the impending heat was life-threatening, not just uncomfortable.

As the intense heat accumulated, overloaded power lines hummed and sagged across cities and suburbs. Power companies fired up idle natural gas plants to generate needed electricity. Volunteers placed thousands of calls to check on senior citizens and disabled individuals. In Vancouver, British Columbia, police responded to a surge in calls involving cardiac arrest and difficulty breathing. Doctors desperate to lower patients’ core body temperatures filled body bags with ice and zipped people inside them.

The heat wave killed approximately 1,000 people in the Pacific Northwest, though heat is often a subtle killer, suggesting the actual toll was higher. The vulnerable died first, including elderly individuals who lived alone or those too poor to afford air-conditioning. Rosemary Anderson, sixty-seven, was found dead in her house, where the indoor temperature reached 99.5 degrees. Jollene Brown, sixty-three, died in her un-air-conditioned living room, found sitting as if she was attempting to stand up but could not overcome the intense heat. Heat waves act as a predatory event, culling the most vulnerable populations.

Nature’s Immediate Collapse

Nature immediately registered the extreme temperatures. Ice, functioning as a thermometer, vanished first. The last of the winter snow in the Cascades melted from shaded areas and glaciers. Without the reflective protective snowpack, the glacial ice melted rapidly, rushing down canyons as silty gray water. This meltwater, carrying ancient sediment, flooded towns and roads. The resulting enormous wash of sediment into the Columbia River was visible from space, photographed by circling satellites.

Migrating salmon sensed these changes immediately in the river temperatures. These fish spend years in the cold Pacific before swimming upstream to their freshwater birthplace to spawn. The fragile journey turned fatal because warm runoff quickly heated the shallow river water. Warm water holds less oxygen because oxygen molecules vibrate faster and escape the molecular bonds, leaving fish struggling to breathe. A wildlife biologist compared this struggle to “breathing with a plastic bag over their heads”.

The stress caused red lesions on the salmon’s iridescent silvery skin. Cottony fungus grew on their backs. Tens of thousands of salmon were suffocating, exhausted, and literally disintegrating in the warmth. The bodies either became meals for predators or washed up on riverbanks to be picked apart by eagles and raccoons. Later, near the coast, the heat wave killed over a billion sea creatures, including limp starfish and the shells of mussels and clams that washed ashore.

Plants and trees across the mountains and valleys were also assaulted by the heat. Rooted in place, these organisms could not seek refuge from the sun and heat that sucked moisture from the soil and their leaves. Broadleaf trees like ash and maple struggled by closing the pores on the undersides of their leaves, effectively holding their breath. Blackberry and blueberry plants drank the moisture out of their own fruit, leaving the fruit withered and dry on the stalks. Some sun-exposed trees tried desperately to cool off by sweating, but their roots sucked air bubbles into their trunks’ veins, causing them to rupture. Scientists suggest that if one had the right microphone, one could have heard the trees screaming.

The Human Artifact: A Crime Scene

The heat we experience today is an entirely human artifact. It is a deliberate, premeditated heat unleashed by the burning of fossil fuels. We have known about the climate consequences of burning these fuels for more than a century. For example, by 1977, Exxon’s in-house models accurately projected climate changes resulting from fossil fuel consumption. Despite warnings delivered to President Lyndon B. Johnson in 1965 and many subsequent presidents, humans continue to burn fossil fuels with reckless abandon. In the US, average global temperatures have risen by 2.2 degrees since the preindustrial era. We are now more than halfway to the 3.6 degrees (2 degrees Celsius) of warming that scientists identified as the threshold for dangerous climate change.

The difficulty in understanding this threat is amplified by the perception of heat as a gradual, linear change. Many nonscientists believe that a few degrees of warming is inconsequential. However, heat is the engine of planetary chaos that amplifies second-order effects like drought and wildfires. For all living things, rising temperature above their Goldilocks Zone means death.

For some, heat results in swift catastrophe. In British Columbia, the record heat led to something resembling spontaneous combustion in Lytton, an old mining camp. On the third day of the heat wave, temperatures in Lytton reached an unholy 121 degrees. A spark from a passing freight train, combined with high winds and extreme dryness, quickly engulfed the town in flames. Mayor Jan Polderman raced his minivan through the village, urging skeptical residents to flee. Jeff Chapman survived by rushing his parents, who were in their sixties, into a trench dug to repair a septic system and covering them with a metal sheet. A power line crashed down across the trench, and his parents perished. A few days later, the entire town of Lytton was smoldering, burned to the ground.

Heat operates as a fast and subtle killer. Worldwide, extreme heat causes approximately 489,000 deaths annually, significantly more than the 250,000 annual worldwide deaths from firearms. Heat penetrates every living cell and melts them like a popsicle, driving entropy and disorder.

A Cautionary Tale: The Mountain Hike

The sudden tragedy of the Gerrish-Chung family in California’s Sierra Nevada foothills illustrates the brutality of modern heat. In August 2021, Jonathan Gerrish, a software engineer, his wife Ellen Chung, their one-year-old daughter Miju, and their dog Oski died on an eight-mile loop hike. The family had recently moved to the lightly forested foothills near the Gold Rush town of Mariposa seeking refuge from Silicon Valley. They were active “city folk” who doted on their daughter.

Gerrish planned the hike using the AllTrails app, aiming to find swimming holes on the Merced River. Their planned route included a steep 2,300-foot climb through Devil’s Gulch. Their brother, Richard, a well-aware outdoorsman, cautioned Gerrish to carry plenty of water and get an early start. They began their hike around 7:30 a.m. when the temperature was in the mid-seventies. Under normal conditions, they calculated completing the loop by 1 p.m..

The trail was exposed, running along a steep, southeastern-facing slope, making it vulnerable to the sun’s brutality. Locals had previously noted the trail was exposed and unwise for a hot day. They reached the river after about an hour, and stopped for a final family selfie at 9:05 a.m.. They began the steep, two-mile ascent back toward their truck around 10:29 a.m.. By that time, the temperature had already climbed to nearly 100 degrees.

The terrain compounded the risks. The recently burned trees along the ascent were leafless and black, offering no shade. The tall grass was sunburned to a golden, crispy brown. By 11:56 a.m., the air temperature hit 107 degrees, with the actual temperature on the sun-exposed trail certainly much higher.

Gerrish attempted to send a text message: “[name redacted] can you help us. No water or ver [over] heating with baby”. The typo (“or ver”) suggests that heat was already inducing cognitive difficulty, which is common during extreme heat exhaustion. The family’s single 85-ounce hydration pack was empty, and they were caught in a brutal heat trap. Over the next twenty-seven minutes, Gerrish attempted five phone calls, but none connected due to lack of service.

The Physiology of Fatal Heat

The human body is fundamentally a heat machine. It works hard to maintain an internal core body temperature of approximately 98 degrees. To manage heat, the body pushes overheated blood toward the skin, using sweat glands to squirt salty liquid onto the surface. Heat dissipates through the evaporation of this sweat. If the air is humid, sweat cannot evaporate effectively, blocking the body’s cooling mechanism.

Heat exhaustion leads quickly to hyperthermia, or abnormally high body temperature. This condition causes dizziness, heat cramps, and eventually heatstroke. There are two main types of heatstroke: classic and exertional. Classic heatstroke affects the elderly, very young, or those with underlying conditions. Exertional heatstroke occurs in otherwise healthy people due to high activity in the heat, like running or hiking.

Hydration alone cannot prevent heatstroke. Drinking water keeps sweat flowing, which aids cooling, but it does not directly cool the inner-core body temperature. One study of a wildfire fighter showed that despite drinking more than twice the water of his peers, his core body temperature still reached 105 degrees, deep in heatstroke territory. Proper hydration can delay heat exhaustion, but it cannot prevent heatstroke itself.

The family was in a lethal feedback loop. Their hearts pumped madly to move blood toward the skin for cooling. This effort increased their metabolism, generating even more internal heat. As blood was diverted to the skin, vital organs like the kidneys, liver, and brain were starved of oxygen. Once the core temperature rises too high, cellular proteins begin to unfold and cell membranes melt. This unraveling leads to massive hemorrhaging, clotting cascades, and organ collapse.

The dog, Oski, was likely in trouble first, as dogs cannot sweat and must rely on panting to release heat, an inefficient process. Oski was a large, muscular dog with a thick coat, making the steep climb brutal in 100-degree heat. One-year-old Miju, strapped in a carrier on her father’s back, was absorbing heat from both Gerrish’s body and the sun. Infants cannot fully release heat because their sweat glands are underdeveloped. They are essentially defenseless against heat, which is why babies are extremely vulnerable in hot cars.

An infant’s smaller blood volume means that when blood is pumped to the skin for cooling, it takes too much blood away from internal organs, potentially causing damage. The family’s single key fob was found on the trail a hundred feet below Gerrish’s body, perhaps suggesting he was panicked or disoriented when he dropped it.

Stephanie Pullman, seventy-two, in Sun City West, Arizona, exemplifies the danger of the thermal divide. She lived on a fixed income of less than $1,000 a month. Her utility company, Arizona Public Service (APS), cut off her power over an unpaid bill of just $51.84. She died in her bed on a 107-degree day from heat exposure. APS data showed the company cut power to customers over 110,000 times in 2018, including over 39,000 cutoffs during the scorching months of May through September. Pullman’s death forced Arizona regulators to ban summer power shutoffs.

In October 2021, the official cause of death for the Gerrish-Chung family was determined to be hyperthermia and probable dehydration due to environmental exposure. The death of this young, active family demonstrated a failure to recognize the extreme risks of a world that is rapidly warming. The invisible force of heat killed them before they fully understood their lives were at risk. It was a tragedy shaped by the reality of living beyond humanity’s biological Goldilocks Zone.

Coming up next: Part 2 details how humans evolved to manage heat and how the modern world challenges—and fails—those evolutionary adaptations.