Hotter days mean livelier nights (and more naps)

Temperatures are rising, and the nights are becoming more alive. Researchers are witnessing more nighttime activity among numerous animals across the globe — alpine ibex in Europe, cheetahs in Africa and the white-lipped peccary (a cute pig-like creature) in South America — to escape extreme heat associated with climate change.

Foraging and hunting for food in the cool night air takes much less energy than in the heat of the day. In the ibex study, the authors hypothesize that “shifting activity toward nighttime may be a common strategy adopted by diurnal endotherms in response to global warming.” Who else is a diurnal endotherm (meaning a warm-blooded animal active during daylight hours)? You, me and the rest of humanity. So in regions suffering extreme heat, are we also going to embrace the dark by going nocturnal?

In some places, the shift is happening. Lisa White, director of strategic forecasting at WGSN Ltd., spoke on the trendforecasting company’s podcast about a shift to nocturnal living, citing increases in late-night scooter rentals and restaurant reservations. In Dubai, beaches have opened for night swimming during the oppressive summer months. And whether it’s runners or Formula 1 racing cars speeding to finish lines, there have been new additions to sporting events taking place at night, too.

Avoiding the peak heat of the day has long been a strategy for hot locations. Mediterranean countries are known for their siestas. Gulf nations have introduced summer bans on outdoor work in the middle of the day.

Now, as the climate crisis intensifies the strength and likelihood of heat waves, changing our daily routines in response to the heat will be a crucial adaptation strategy. In April 2023, India either closed schools or revised school timings to very early in the morning so children could be home before temperatures rose to dangerous levels. Even places not known for being too hot likely will need to grapple with more flexible schedules in the future: As heat waves gripped southern Europe in July, doctors in Germany called for siestas to help workers remain productive.

So it seems like a shift to “nap culture,” as White puts it in the podcast, will be inevitable in some situations. That’s something I’d embrace — short naps have been proven to help reduce body temperature and would make up for sleep lost during hot nights.

But why not make like a peccary and eschew the sun completely?

To answer that, we should take a look at the nocturnal routines for other diurnal animals. It’s clear there are some big downsides. By going out in the dark, cheetahs are more likely to lose their prey, even ones they’ve killed themselves, to larger beasts such as lions and leopards. Ibex open themselves up to more predation from wolves, and struggle to move around on the steep rocky slopes where they live.

For humans, giving up the daylight likely would cause us some issues, too.

Christian Clot, explorer and chief executive officer of the Human Adaptation Institute, recently completed a research trip called Deep Climate. He led 10 men and 10 women across equatorial rainforest, arid desert and a polar environment for three 40-day periods to uncover the effects of humid heat, dry heat and cold on their bodies and brains.

During the desert expedition in Saudi Arabia, temperatures reached highs of 113F: “Less than we hoped for,” Clot told me. Between 5 a.m. and 9:30 a.m., they would be on the move before having to stop because of the heat.

They would then wait in shade until about 5 p.m. when they would walk for another two or three hours. I asked Clot why they didn’t just move at night rather than waiting around for eight hours during the day. He told me that the cool temperatures at night were essential for grabbing enough sleep.

Even if you could become fully nocturnal — if, say, you’re lucky enough to have air conditioning to enable daytime slumbers — our circadian rhythms pose an immovable hurdle. Although they vary from person to person, our internal body clocks are influenced heavily by light, regulating everything from sleep, temperature and hormones.

Numerous studies have shown that working night shifts — permanently or on a rotating schedule — comes with a host of health problems, increasing the risk of diabetes, heart disease and even cancer.

In the case of outdoor work — of critical importance as we build the infrastructure needed for the energy transition — overnight work will become increasingly necessary in the very hottest periods. But we shouldn’t pretend that it’s a solution without cost.

What’s clear is that as we seek to adapt to the effects of climate change, we’ll need to have serious conversations about moving activities — business and pleasure — to cooler parts of the day. In other words, employers are going to have to embrace nap culture.