The Heat Will Kill You First

1. Heat is an Invisible, Active Force Shaping Our World

The kind of heat I’m talking about here is not an incremental bump on the thermometer or the slow slide of spring into summer. It is heat as an active force, one that can bend railroad tracks and kill you before you even understand that your life is at risk.

Heat's underestimated power. Heat is often perceived as a gradual change in temperature, but it's a potent, often invisible force with the capacity to cause widespread destruction and death. It's not merely an inconvenience; it's a fundamental driver of planetary chaos, capable of melting ice sheets, igniting wildfires, and disrupting ecosystems.

The Gerrish family tragedy. The tragic deaths of the Gerrish family in the Sierra Nevada foothills serve as a stark reminder of heat's potential lethality. Their story underscores the importance of understanding the risks of hiking in extreme heat, even on seemingly familiar trails. The family's lack of awareness, combined with the unforgiving conditions, led to a devastating outcome.

Beyond incrementalism. The book challenges the conventional understanding of heat as a linear, controllable phenomenon. Instead, it presents heat as an active agent, capable of causing sudden and catastrophic changes. This shift in perspective is crucial for recognizing and responding to the growing threat of extreme heat in a rapidly warming world.

2. Humans Evolved Clever Heat Management Systems

By managing heat, humans were able to go farther from water holes, begin long-distance travel, and expand their hunting range.

Evolutionary adaptations. Humans, like all living things, have evolved sophisticated mechanisms for managing heat. From bipedalism to eccrine sweat glands, these adaptations allowed our ancestors to thrive in diverse environments. However, these systems are optimized for a specific range of temperatures and are increasingly challenged by the rapid pace of climate change.

The importance of sweating. The development of eccrine sweat glands, which are unique to humans, was a pivotal moment in our evolutionary history. This efficient cooling system allowed our ancestors to hunt and travel long distances in hot climates, giving them a significant advantage over other species.

Limits to adaptation. While humans are remarkably adaptable, there are limits to our ability to cope with extreme heat. As temperatures rise, our bodies struggle to maintain a stable internal temperature, leading to heat exhaustion, heatstroke, and ultimately, death. Understanding these limits is crucial for protecting ourselves and others in a warming world.

3. Urban Heat Islands Expose Deep Inequities

In a heat wave, wealth can afford twenty-five degrees of coolness.

The urban heat island effect. Cities, with their abundance of concrete, asphalt, and steel, trap and amplify heat, creating urban heat islands that can be significantly hotter than surrounding areas. This phenomenon disproportionately affects low-income neighborhoods with less green space and fewer resources to combat the heat.

Temperature apartheid. The book highlights the stark inequalities in access to cooling resources, with wealthier residents able to afford air-conditioning and other heat-mitigation measures while poorer residents are left to swelter in uninsulated homes. This "temperature apartheid" exacerbates existing social and economic disparities.

Chennai and Phoenix. The stories of Anjalai in Chennai and Leonor Juarez in Phoenix illustrate the daily struggles of people living in extreme heat with limited resources. These personal narratives underscore the urgent need for equitable solutions to address the growing threat of urban heat.

4. Extreme Heat Drives Migration of All Living Things

As the temperature rises, it will drive a great migration—of humans, of animals, of plants, of jobs, of wealth, of diseases.

A world on the move. As temperatures rise, living things are forced to migrate in search of more hospitable climates. This mass movement includes humans, animals, plants, and even diseases, creating new challenges and uncertainties for ecosystems and societies.

The lure of cheaper land. Despite the risks, many people are moving to areas with high climate risks, drawn by lower housing costs and access to nature. This trend highlights the complex factors that influence migration decisions and the need for better information and planning to ensure safe and sustainable communities.

The story of Melanie Elliott and Andrew McGowan. The story of Melanie Elliott and Andrew McGowan, fleeing Hurricane Harvey, illustrates the human side of climate migration. Their journey to San Diego, driven by the need to escape the constant flooding in their hometown, underscores the growing displacement caused by extreme weather events.

5. Heat Weaponization and the Weaponization of Ignorance

Part of their strategy is to funnel migrants through the hottest, most dangerous regions of the border.

Heat as a tool of control. The book explores the disturbing ways in which heat can be weaponized, both intentionally and unintentionally. The US Border Patrol's strategy of funneling migrants through the most dangerous regions of the desert is a chilling example of how heat can be used to deter and harm vulnerable populations.

The Gerrish family tragedy. The tragedy of the Gerrish family is not just a consequence of bad luck and poor decision-making in the wild. It was a tragedy that was shaped by our larger failure to reckon with the risks of life in a rapidly warming world, and with the nature of heat itself.

The weaponization of ignorance. The book also examines how ignorance and denial can be weaponized, allowing those in power to ignore the suffering of others and perpetuate systems that exacerbate climate change. This form of weaponization is particularly insidious, as it allows harm to be inflicted without direct intent.

6. Attribution Science Connects Extreme Events to Climate Change

To me, science is—or can be—a tool for justice. Extreme event attribution is the first science ever developed with the court in mind.

Linking events to climate change. Extreme event attribution is a revolutionary new field of climate science that allows scientists to determine the extent to which specific extreme weather events are caused by human-induced climate change. This science has the potential to hold polluters accountable for the damages caused by their actions.

Friederike Otto's work. The work of Friederike Otto, a leading figure in attribution science, is highlighted. Her research has demonstrated that many extreme heat waves would have been "virtually impossible" without climate change, providing a powerful tool for understanding and communicating the impacts of our actions.

Implications for legal liability. The ability to attribute extreme weather events to climate change opens the door to legal remedies, allowing individuals and communities to sue greenhouse gas emitters for the damages they have caused. This could have profound implications for the fossil fuel industry and the future of climate policy.

7. The Ocean's Role in Absorbing and Redistributing Heat

Without the ocean, the atmosphere would be a lot hotter than it already is.

The ocean as a heat sink. The ocean has absorbed about 90 percent of the additional heat trapped by greenhouse gases, acting as a crucial buffer against the worst effects of climate change. However, this absorption comes at a cost, leading to rising ocean temperatures, acidification, and other harmful changes.

Marine heat waves. The book explores the phenomenon of marine heat waves, which are becoming more frequent and intense due to climate change. These events can devastate marine ecosystems, causing mass die-offs of coral reefs, kelp forests, and other vital habitats.

Impacts on weather patterns. The ocean plays a critical role in regulating global weather patterns, and changes in ocean temperature can have far-reaching consequences. A warming ocean can intensify storms, alter rainfall patterns, and disrupt ocean currents, leading to unpredictable and potentially catastrophic weather events.

8. The Fragility of Food Systems in a Warming World

The largest single global change that threatens food security is high temperature.

Heat's impact on crops. Extreme heat poses a significant threat to global food security, disrupting plant metabolism, increasing water demand, and making crops more vulnerable to pests and diseases. Declining crop yields could lead to widespread food shortages and social unrest.

The case of corn. Corn, a staple crop in many parts of the world, is particularly vulnerable to heat stress. Rising temperatures can disrupt pollination, reduce yields, and increase the risk of aflatoxin contamination, threatening both human and animal health.

Adaptation strategies. The book explores various strategies for adapting food systems to a warming world, including developing heat-resistant crop varieties, improving irrigation techniques, and shifting to more sustainable agricultural practices. However, these efforts may not be enough to offset the growing threat of extreme heat.

9. The Sweat Economy: Laboring in the Heat

Rich countries have brought much of their economy indoors where air-conditioning is a possibility, but many developing economies rely on labor-intensive outdoor work.

Unequal exposure. The book examines the "sweat economy," in which low-wage workers are forced to labor in extreme heat with limited protection. This disproportionately affects farmworkers, construction workers, delivery drivers, and others who work outdoors, exacerbating existing social and economic inequalities.

Health and productivity impacts. Heat stress can lead to a range of health problems, from heat exhaustion and heatstroke to chronic kidney disease. It also reduces worker productivity, leading to significant economic losses.

The need for worker protections. The book calls for stronger regulations to protect workers from heat exposure, including mandatory breaks, access to cool water and shade, and training on heat-related illnesses. These measures are essential for ensuring the health and safety of those who labor in the heat.

10. The Arctic's Melting Ice: A Planetary Warning

Seeing this glacier makes you realize that things you think will always be there might not be. That’s quite a thing to get your head around.

Antarctica's fragility. The book explores the rapid melting of ice sheets in Antarctica, particularly the Thwaites Glacier, which is destabilizing and could lead to catastrophic sea-level rise. This melting is driven by warming ocean currents that are eroding the ice from below.

The polar bear's plight. The story of the polar bear on Baffin Island serves as a poignant reminder of the devastating impacts of climate change on Arctic wildlife. As sea ice disappears, polar bears struggle to hunt seals, leading to starvation and population decline.

A call for action. The book emphasizes the urgent need to reduce greenhouse gas emissions and protect the Arctic ice sheets. The fate of polar bears, coastal cities, and the entire planet depends on our ability to take decisive action to address the climate crisis.

11. Adaptation, Mitigation, and the Future Beyond Goldilocks

We can save the future or we can save the past, but we can’t do both.

The need for adaptation and mitigation. The book concludes with a call for both adaptation and mitigation strategies to address the growing threat of extreme heat. Adaptation involves making changes to our built environment and lifestyles to cope with a warmer world, while mitigation involves reducing greenhouse gas emissions to slow the pace of climate change.

The thermal divide. The book warns of a widening "thermal divide" between those who can afford to protect themselves from extreme heat and those who cannot. Addressing this inequality requires equitable policies and investments that prioritize the needs of vulnerable populations.

A call to action. The book ends with a message of hope, emphasizing that we still have the power to shape our future. By taking bold action to reduce emissions, adapt to a warmer world, and protect the most vulnerable among us, we can create a more just and sustainable future for all.

Last updated: April 4, 2025