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The year is 2050 and your morning is not off to a good start.
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School is closed for yet another heat day,
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meaning the kids need to stay home and the AC needs to stay on.
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Your usual babysitter can’t come help
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because the rails for their commuter train were warped by the heat.
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And to make matters worse, your dog is desperate for a walk,
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but the pavement is hot enough to give third degree burns
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to any paw or person that touches it.
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In many parts of the world, this sweltering future is already here.
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On average, heat waves are happening more often with greater intensity
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and for longer durations.
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But according to a 2022 projection,
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by 2050, Earth’s mid-latitudes could be experiencing extreme heat
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between 90 and 180 days a year,
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with tropical regions enduring even more.
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So, how hot is too hot, and what can people do to handle the heat?
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While human bodies are decent at managing temperature,
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our cooling mechanisms only work under the right conditions.
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When air temperatures climb,
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the hypothalamus tells blood vessels near the skin to widen,
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allowing more blood to flow near the body's surface and release heat.
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This hormonal cascade also turns on our sweat glands.
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As sweat evaporates, it pulls the heat from our skin.
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But if humidity is high, the rate of evaporation slows and eventually stops.
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Scientists use this principle to track humidity with a metric
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called wet-bulb temperature,
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in which they wrap a wet, room temperature cloth around a thermometer
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to see if evaporation will lower the reading.
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If it doesn't, it's too humid for sweat to cool us off.
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A wet-bulb temperature of roughly 35°C
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is generally considered the limit of human survival,
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though current temperatures rarely reach this threshold.
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The US National Weather Service uses the relationship between humidity
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and air temperature as the basis for their heat index.
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As those two metrics rise, so too does the heat index;
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and heat is considered dangerous
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if the index climbs above 39.4°C.
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That’s 103°F.
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But even a lower heat index can be hazardous over multiple days.
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A heat wave is a streak of two or more days of unusually hot weather
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for a place and season.
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For example, a string of 32°C days in Houston, Texas,
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is standard in the summer,
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but would constitute a heat wave in March.
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And the impact of these events touches nearly every aspect of daily life.
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Imagine a June heat wave strikes a tropical city.
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The first to experience effects are outdoor workers.
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Their excessive sweating leads to dehydration and muscle pain
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known as heat cramps.
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If they push on, their conditions could worsen
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to heat exhaustion and even heat stroke—
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a life-threatening ailment that occurs when a body’s temperature exceeds 40°C.
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Medical emergency calls spike across the city,
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often for children and people who are pregnant or elderly.
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The heat also increases hospital visits for heart, kidney,
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and lung-related conditions,
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creating an influx of patients that threatens to overwhelm medical providers.
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Over the following week, the city slows to a crawl.
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Schools and construction sites close.
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Airplanes need to reduce their weight limits to take off,
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bumping countless travelers from their flights.
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Restaurants shut down as overheated kitchens become unbearable.
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Residents who remain inside with air conditioners stay safe.
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But blasting AC isn’t cheap,
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and many families have to choose between keeping cool and staying fed.
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Either way, if the heat continues,
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the stress of these air conditioners could overwhelm the power grid,
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potentially leading to city-wide outages.
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These consequences are all very real.
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Each year, close to 500,000 people die due to excessive heat,
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and these extreme conditions are only growing more common.
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We can limit medical impacts by seeking help for heat-related illnesses,
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staying hydrated,
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and keeping people cool through public access to water and AC.
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But don’t let anyone tell you 1 to 2 degrees doesn’t matter.
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It will change our very way of life.
