The Heat Will Kill You First

Heat, an invisible but deadly force, stalks Earth’s living things at escalating levels.

In 2021, Pacific Northwest residents suffered an extreme heat wave produced by a suffocating heat dome. In 24 hours, Portland’s temperature jumped from 76^oF to 114^oF. Mountain ice melts brought swirling floods and mudslides so intense that satellites could see their “gray plumes.” Salmon struggled as if they were “breathing with a plastic bag over their heads.” Baby hawks abandoned over-heated nests, berries desiccated on the stalk, and broadleaf trees withered and died. Power companies struggled to keep up with unprecedented demands. The human death toll after 72 hours was estimated at 1,000. 

“The sun feels like the barrel of a gun pointed at you. Plants look like they’re crying. Birds vanish from the sky and take refuge in deep shade. Cars are untouchable. Colors fade. The air smells burned. You can imagine fire even before you see it.”

Most people see global warming as a slow, incremental process, but the Earth is quickly heating because of fossil fuel emissions. The planet is more than halfway to the 3.6°C temperature increase scientists recognize as a tipping point. Climate impacts such as drought, fires, and sea level rise are “second-order” effects. The primary planetary crisis is relentless heat, resulting in coastal flooding, dried out plants and trees, thawed permafrost, and exploding bug populations.

The story of a healthy young couple, Jonathan Gerrish and Ellen Chung, and their baby Miju, who died of heatstroke – along with their dog – while hiking in the Sierra Nevada foothills in 2021 demonstrates that heat can kill even the fittest human beings. Disregarding the dangers of excess heat may have shaped their tragedy.

“If there is one idea in this book that might save your life, it is this: The human body, like all living things, is a heat machine. Just being alive generates heat. But if your body gets too hot, too fast — it doesn’t matter if that heat comes from the outside on a hot day or the inside from a raging fever — you are in big trouble.”

As people try to mitigate or flee the impacts of global warming, the poor will fare worse than the rich, who can add air conditioning or change locations. In 2019, The Lancet reported that 489,000 people died from extreme heat — more than the deaths caused by all other 2019 natural disasters combined. Global warming also compounds societal and economic challenges. Stephanie Pullman, 72, of Phoenix, died of heat exposure in her home because she couldn’t pay the $51.84 balance on her electric bill. In her city and others, temperature is now a “signifier of class, wealth, and often, race.”

Eventually, however, the relentless heat will affect everyone. Half of the people on Earth will experience life-threatening heat by 2100. 

Earth’s earliest organisms learned to mitigate temperature changes.

About 260 million years ago, “warm-blooded” animals developed the ability to create bodily heat sources, giving rise to humans with large brains. Animals evolved in diverse ways to cool themselves: elephants flap their ears, koalas hug cool trees, kangaroos spit on their arms, hippos roll in mud, lions climb trees, bees build cooling structures. Between 40% and 70% of 4,000 terrestrial animal species have moved to cooler climates over the past decade. Marine creatures are moving four times faster. Trees also migrate, at various speeds depending on their variety. The white spruce, moving north at some 60 miles every 10 years, is the quickest. Such adaptions determine which organisms survive and which ones go extinct. Take the human body, which is optimized for the environment as was for the past 10,000 years, the “Goldilocks zone.” Now Earth is warming too quickly for easy adaptation.

“When it comes to heat management, we are like actors in Hollywood’s silent era who suddenly find themselves cast in speaking roles. We know the script, but our skills are no longer well-matched for the world we live in.”

After 1970, the planet’s heat jumped higher than in any other 40-year stretch, and “the eight years between 2015 and 2022 were the hottest on record.” Since the 1990s, the direct effects of extreme heat have cost $16 trillion globally.

John Orlowski of the nonprofit No More Deaths, which helps migrants cross the Mexico-United States border, says thousands die of heat exhaustion in the borderlands every year. White crosses mark the last locations of some who did not make it through this “ghostly boneyard of heat.”

A new “age of accountability” could force companies to pay billions for contributing to climate change.

By the 1950s, climate scientists were already worried about spreading deserts and melting polar ice. A landmark, 1984 paper predicted that a global temperature increase of three degrees could cause catastrophic impacts. NASA’s “godfather of modern climate science,” James Hansen, told Congress in 1988 that the Earth had never been warmer and outlined global warming’s “cause and effect relationships to the greenhouse effect.” He presaged drastic outcomes, such as heat waves. Today, climatologists are particularly concerned about extreme heat waves in areas with vulnerable populations.

“The discussion about ‘loss and damages’ is so fraught in international climate talks, with the leaders of rich, industrialized nations in the Global North pushing hard to keep the topic out of the negotiations while politicians and activists in the climate-ravaged countries of the Global South say, very bluntly, ‘We’re the ones who are suffering. We’re the ones who are dying. You owe us, and you need to pay’.”

Global agriculture is producing smaller yields, fomenting hunger and violence. The number of people facing food insecurity has increased from 135 million to 345 million since 2019. In 2022, 45 countries approached famine. To feed a global population projected to be 10 billion by 2050, agricultural output must increase by half. That also requires outdoor workers, who face increased health risks in high heat. Rising heat is the “largest single global change that threatens food security” according to plant biology professor Donald Ort of the University of Illinois, and it makes some plants more susceptible to pests, toxins, and disease.

Even corn, which is more weather tolerant than many crops, can’t survive such extreme heat waves and drought. Plant geneticists are working to design heat-resistant crops, and to find hardy replacements. Raising livestock is an even greater challenge because it’s hard to keep animals cool. New protein sources such as fungi, insects, or man-made meats may become necessary to feed the world.

The effect of climate change on the ocean “may have the biggest impact on our future.”

A 2013 Pacific heatwave nicknamed “the Blob” killed microscopic algae in top ocean layers, disrupting the entire food chain, from tiny krill to sea lions and whales. Over two years, it damaged fisheries from Alaska to California, changed weather patterns, and sparked wildfires.

“If we stopped emitting CO2 tomorrow, some reefs would probably survive. But if we go on a few more decades, I think the reefs are gone. Over geological time scales, they will come back, depending on how long it takes the ocean chemistry to recover. But it’s likely to be at least 10,000 years before anyone sees a reef again.” (Ken Caldeira, Senior Climate Scientist, Breakthrough Energy, California)

The profoundly changing oceans redistribute heat from the poles to the tropics via the Gulf Stream. One notable catastrophe is that 90% of the large fish known since the 1950s are gone. Worldwide, heat waves are causing mass migrations of ocean creatures and killing sea life. Sea stars, the natural predators of sea urchins, can’t live in the hotter waters where the urchins are now killing Northern California’s kelp bed ecosystem. Coral reefs are disappearing at shocking rates. Some 93% of Australia’s Great Barrier Reef has experienced deadly coral “bleaching.” Climate scientist Ken Caldeira believes that “by mid-century, pretty much every reef in the world will be eroding away.” After thriving for 250 million years, coral reefs could disappear in a generation.

Unstable ice sheets at Earth’s poles could cause rising sea levels which impact coastal cities.

A warming of one or two degrees in Antarctica could mean the collapse of ice sheets three miles thick, holding 70% of the planet’s water. Satellite images show thinning ice spanning the continent. After the sudden collapse of the Larsen B ice shelf, glaciers behind it began flowing far more quickly into the sea. If all Greenland melts, the result will be 22 feet of sea level rise; if Antarctica melts, the rise could equal 200 feet.

Heat, drought, and floods create fresh opportunities for pathogens and microbes. Mosquito-borne dengue fever has increased tenfold since 1970, a danger blamed on global warming. By 2080, 60% of the human population could be at risk for hantavirus, malaria, anthrax, cholera, influenza, Zika, and SARS-CoV. Stanford University epidemiologist Stephen Luby cites the “existential threat” of even more serious diseases, such as the equally transmissible Nipah virus, which kills 75% of its victims. People usually compare Covid-19 to the 1918 influenza epidemic which caused at least 50 million deaths, but understanding it as a precursor of the future may be more accurate.

Thawing Arctic land releases germs that have lain dormant for thousands of years. These ancient pathogens and parasites can jump to migrating animals, creating optimal conditions for spreading a pandemic.The coming decades are likely to see 300,000 new encounters between species, leading to 15,000 viruses entering new hosts.

“Nature is complex. I don’t like the narrative that says we are one tick bite away from catastrophe. But at the same time, I can’t say it won’t happen.” (Dennis Bente, Galveston National Laboratory)

Ticks cannot withstand cold, dry climates, but deer ticks carrying Lyme disease are becoming more prevalent. Hyalomma ticks carry Crimean Congo Hemorrhagic Fever, somewhat like Ebola.

Air conditioning in homes and cars opened new frontiers for human migration and development.

In 1974, scientists found that the chlorofluorocarbons (CFCs) used in air conditioners, refrigerators, and aerosol sprays could deplete Earth’s ozone layer. CFCs were eventually banned, but they were replaced by hydrofluorocarbons (HFCs), greenhouse gases about 15,000 times more potent than CO2. By 2050, the world may contain more than 4.5 billion air conditioning units.  Blackouts and brownouts will become common as electrical consumption peaks.

The question is not whether superheated cities will be sustainable, but sustainable for whom and at what cost. The risk of the “urban heat island effect,” has tripled over four decades, putting billions of people in peril. Air conditioning created a divide “between the cool and the damned,” as people decide they could not exist without “cheap cold air.” Cities must adapt by designing hyperefficient buildings and reworking existing ones. Urban areas must become more population dense, replace cars with bicycles, and create more green spaces. For example, take Paris, where a 2003 heat wave spiked temperatures to 104, killing 15,000 people. The city’s iconic zinc roofs trap excessive amounts of heat, and many top-floor dwellers died during the heat wave. Historians have resisted suggestions to paint them white or plant gardens on them, but climate change may require changes to culturally significant buildings. Paris’s famed Champs-Élysées is being re-envisioned as “an extraordinary garden” by 2035, to avoid an “apocalyptic future” of blackouts, heat-related deaths, traffic jams, and food shortages.

“We have entered a new climate and energy paradigm. We need a social and cultural transformation on a level that I’m afraid people who have been in power for the last 20 years cannot really imagine.” (Alexandre Florentin, Paris City Councilman)

“New Urbanists” are working to bring natural elements like trees into cities where entire ecosystems have been paved. Trees are “superheroes” in fighting climate change. They inhale CO2, exhale oxygen, filter the air, and provide cooling shade, but the number of Earth’s trees has dropped by 46% since the beginning of civilization because people cut them down or plant them in poor locations.The Global Urban Tree inventory warns that “midrange” global warming’s heat and drought could kill 75% of urban trees by 2050.

On the final day of 2015’s UN Climate Summit, COP21, leaders of 195 countries committed to a two-degree limit on global warming. However, industrial countries continue to expel some 36 billion tons of C02 annually – an unprecedented pace, even during mass extinctions. Now, says Paris City Councilman Alexandre Florentin, people must accept humanity’s three current options: “We roast, we flee, or we act.” 

The preferred way to stop heating Earth’s atmosphere is to stop releasing greenhouse gases into it.

Melting ice sheets have profound effects on climate — altered weather patterns, sea level rise, and release of methane, a potent greenhouse gas. Disappearing ice means fewer bears in the Arctic wild. Baffin Island offers a fast-changing landscape of shrinking glaciers, some of which have retreated a mile. Its polar bears are under extreme threat; for polar bears, “heat equals starvation.” 

Unless people stop burning fossil fuels, future generations will live outside the Goldilocks zone, in a land where relentless heat rules. Changing course requires solid science, political leadership, and a sense of personal connection to the Earth. Decades of innovation are starting to decarbonize our world. Clean energy is becoming cheaper than fossil fuels. Technology can help humankind survive for a while. People can move to cooler places and learn to live with the suffering — but alarming changes will inevitably occur.

“We are deciding, without quite meaning to, which evolutionary pathways will remain open to us and which will be forever closed. No other creature has ever managed this, and it will, unfortunately, be our most enduring legacy.” (Elizabeth Kolbert, author, The Sixth Extinction: An Unnatural History)

The Earth has experienced more than one era in which almost all life perished. Take the Permian extinction — a massive onslaught of volcanic activity and intense heat some 300 million years ago. The planet recovered, but it took ten million years.