6 Ways Humans Influence the Weather

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iStock

If you've ever spent any length of time on Twitter, you've probably heard a thing or two about humans secretly having the ability to control the weather. While that talent only exists in movies, we humans and our everyday activities do indirectly influence the weather in ways that go far beyond our production of greenhouse gases. Climate scientists and meteorologists have documented these effects for years. 

1. CITIES FORM HEAT ISLANDS.

sunlight shining through city streets and buildings
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They're not exactly wrong when they call the capital of Georgia "Hotlanta." Most populated areas generate heat simply by existing. The dense web of asphalt roads, concrete sidewalks, brick facades, and tar roofs are able to absorb a significant amount of heat from the daytime sun, even in the dead of winter. This human-made insulation, called the urban heat island effect, keeps city centers a tad hotter on hot days and a little less cool on cold days.

While the urban heat island effect might make you think of burning-hot asphalt, it's actually most noticeable during winter storms when air temperatures are hovering right around freezing, putting you right on the line between wet snow, an icy mix, or a cold rain. The artificial warmth from cities can influence the precipitation type in these storms, potentially lowering a city’s snow accumulations compared to its suburbs.

A 2011 study published in the Journal of Applied Meteorology and Climatology [PDF] also found that the urban heat island effect can have a pronounced impact on thunderstorms that form over cities. The researchers studied 91 summertime thunderstorms that formed over Indianapolis, Indiana, and found that their research models could not replicate those thunderstorms without the influence of the urban area beneath the storms.

2. CROPS JACK UP THE HUMIDITY.

wheat crops growing in a field
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If cities can absorb the heat of the day and make it even hotter, you can imagine how the vast swaths of crops that blanket the countryside can also affect our daily weather. Instead of making it hotter, crops can make a humid day unbearable by sending moisture levels almost off the charts on a putrid summer's day.

Corn crops are notorious for pushing dew points—the temperature at which the air reaches 100 percent humidity—up above 80°F in the middle of the summer, creating a dangerous heat index that soars far above 100°F. Compare that to a muggy day, which has a dew point around 70°F, or a comfortably dry day with a dew point in the low 50s.

The harvest can have the opposite effect. In 2016, Mesonet, a network of weather stations in Oklahoma, found that newly harvested areas of wheat in the northern part of the state were hotter and had a lower dew point than their cooler but muggier surroundings.

3. PAVING INCREASES THE INTENSITY OF FLOODS.

multilane highway with heavy traffic
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Our obsession with construction doesn't stop at influencing temperatures. Paving over porous earth with relatively impervious materials like asphalt and concrete has also had a major impact on flooding during heavy rain events. Fewer places for rainwater to escape means that the sudden influx of water builds up in urban areas or runs off and inundates places that had never seen flooding before.

4. NUCLEAR POWER PLANTS CAN TRIGGER NUCLEAR-EFFECT SNOW.

nuclear power plant during the winter
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Lake effect snow is a yearly phenomenon across North America’s Great Lakes, where bitterly cold air flows over the warm lake water, triggering convection that blows ashore as heavy bands of snow. The bands of snow are so intense that communities can see many feet of snow in one day, sometimes accompanied by thunder and lightning.

It's not only bodies of water that can cause this phenomenon. Nuclear power plants release large amounts of steam during the course of their operations, and on cold mornings when there's enough moisture in the air, locations immediately downwind of a power plant's steam stacks can experience "nuclear-effect snow," which forms through similar means as lake effect snow. The phenomenon isn't limited to just nuclear power plants, but they produce enough steam that it’s noticeable over a large area. Thankfully for residents nearby, it doesn't produce much snow—and it’s not radioactive.

5. URBAN DENSITY CAN AMPLIFY WINDS.

girls talking selfie in paris as wind whips their hair around
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If you've ever walked down a city street on a windy day, you’ve probably noticed that it sometimes feels like you're being buffeted by air shot out of an industrial fan instead of a regular windstorm. Dense building construction can amplify the winds and cause gusts to blow much faster than they would out in the open. This wind tunnel effect can cause serious damage, blowing out windows, knocking down trees, and sending dangerous debris hurtling toward the busy streets below.

The principle is the same as holding your thumb over the end of a garden hose to make the water spray out faster—the wind speeds up dramatically as it presses between the buildings. This is also why you should never take shelter underneath a bridge during a tornado. The tornadic winds squeezing underneath the bridge will speed up, increasing the odds that you’ll be pelted by debris or sucked out into the open.

6. JETS CREATE CIRRUS CLOUDS.

plane exhaust in the sky with a foreground of bushes and trees
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The simple act of flying can also create intricate patterns of clouds in the sky that wouldn't have formed had we not perfected the art of air travel. The hot water vapor produced by the engine exhaust of a high-flying jet aircraft leaves contrails, short for condensation trails, in its wake. Contrails can dissipate right away or linger for hours depending on upper-level humidity and winds. These man-made cirrus clouds are most common at high cruising altitudes, but places like the Arctic and Antarctic get cold enough that contrails can form at or near ground level.

Editor's note: This story, which originally ran in 2016, was updated in August 2018.

The Best Place to Park at the Mall, According to Science

Diy13/iStock via Getty Images Plus
Diy13/iStock via Getty Images Plus

It’s Black Friday, and you are entering the battlefield: a mall parking lot. You’re determined to nail that doorbuster deal, and quantities are limited. The field is already full of other combatants. You must find the perfect parking spot.

Do you grab the first one you see, or drive as close to the mall as you can and hover? Or, do you choose a tactic that lies somewhere between?

Parking at the mall has long frustrated drivers and taxed the minds of traffic engineers—but after working on the problem for three years, physicists Sidney Redner of the Santa Fe Institute and Paul Krapivsky of Boston University have gotten closer to a winning strategy. “There are lots of studies of parking lots, but it’s just that they’re so complicated, you don’t get any insight into what’s actually happening,” Redner tells Mental Floss.

Redner and Krapivsky, whose work employs statistical physics to make sense of large systems, simplified the messy dynamics of a parking lot by modeling it with a one-dimensional grid of cells, each representing a parking space. They tested three simple, yet realistic, parking strategies using basic probability theory. Their model tested the following strategies to see which one resulted in least time spent walking and driving in the parking lot:

Meek Strategy: Meek drivers park in the first open space they see, however distant it is from the mall. As a result, they often spend the most time walking to and from the mall.

Prudent Strategy: Prudent drivers look for the first open spot but then keep driving toward the mall. They continue to drive until they see a parked car and then park in the best open spot between that first open spot and that first parked car. There may be a block of open spaces between the first open space and the first parked car. From that block of open spaces, they choose the one closest to the mall.

Optimistic Strategy: Optimistic drivers drive as close to the mall as possible and look for a parking space close to the entrance. If they see one, they grab it. If there are none, they backtrack and choose the first open space they see. Optimistic drivers probably spend the most time driving and the least time walking. In the worst-case scenario, they end up parking back where a meek driver would have parked.

Naturally cautious drivers are more likely to default to the meek mode, while aggressive drivers often use the optimistic strategy, well, aggressively. And most drivers have tried something like the prudent method.

So, which is your best bet in a crowded mall parking lot this holiday season?

In the experiments, the prudent strategy fared best, followed closely by the optimistic strategy. The meek strategy finished a distant third (“It’s hard to comprehend just how bad it is,” says Krapivsky, a self-described meek driver).

And even better: The more crowded the lot, the better the prudent strategy works, he adds.

One clear takeaway from the study is that meek drivers may want to ramp up their parking skills before going to the mall. “You don't want to park on the very outskirts of the lot, like a mile away from the stores. You want to go to the first place there’s an open spot and park somewhere in that first open area,” Redner says. They published their findings in the Journal of Statistical Mechanics [PDF].

The researchers say this is the best of the strategies they tested, but it has its limitations. It does not take into consideration competition among a sea of drivers all looking for parking spaces at the same time, and it doesn’t include (perhaps optimistically) the psychological aspects of operating a vehicle. “We are not rational when we are driving,” Krapivsky tells Mental Floss.

The researchers’ one-dimensional grid model also assumed that there would be one car at a time entering the lot through one entrance, unlike messier lots in the real world, where many cars enter from a multitude of entrances.

The optimal parking strategy, one that would best all others every time, has yet to be found. In their research, though, Redner and Krapivsky are homing in on one that integrates the more complicated aspects of parking.

For now, science says prudence is a virtue in the parking lot. And while the meek might inherit the Earth, they certainly won’t find the best parking space at the mall.

'Lost Species' of Tiny, Rabbit-Sized Deer Photographed in Vietnam for the First Time in 30 Years

Global Wildlife Conservation
Global Wildlife Conservation

The silver-backed chevrotain, also called the Vietnamese mouse-deer, is elusive. It's so elusive that scientists had feared it was extinct after none had been photographed for decades. But as The Washington Post reports, the first images taken of the mammal in nearly 30 years prove that the species is still alive in the woods of Vietnam.

No larger than small dogs, chevrotains are the tiniest ungulates, or hoofed animals, on Earth. They have vampire-like fangs and skinny legs that support their bodies. Silver-backed chevrotains are characterized by the silver sheen of their tawny coat.

The tiny population native to Vietnam has been devastated by poachers in recent decades. That, and the animal's natural shyness, make it incredibly difficult to study. Before this most recent sighting, the last time scientists had recorded one was in 1990.

Global Wildlife Conservation, the Southern Institute of Ecology, and the Leibniz Institute for Zoo and Wildlife Research teamed up in hopes of documenting the lost species. Researchers interviewed residents and government forest rangers in the Vietnamese city of Nha Trang about the silver-backed chevrotain, looking for tips on where to find one. Residents said that while populations had been hit hard by hunting, the animals were still around.

Based on this local ecological knowledge, scientists set up three camera traps in the Vietnamese woods. In just five months, they captured 275 photographs of the little mouse-deer. They then installed 29 additional cameras and snapped 1881 new images in that same length of time.

“For so long this species has seemingly only existed as part of our imagination," Global Wildlife Conservation associate conservation scientist An Nguyen said in a statement. "Discovering that it is, indeed, still out there, is the first step in ensuring we don’t lose it again, and we’re moving quickly now to figure out how best to protect it.”

Now that a silver-backed chevrotain population has been located, researchers plan to conduct the first-ever comprehensive survey of the species. Once the data is collected, it will be used to build a plan for the species' survival.

[h/t The Washington Post]

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