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Potentially Deadly Heat and Humidity Levels Are Already Here and Rising

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Potentially Deadly Heat and Humidity Levels Are Already Here and Rising
Doha, Qatar is one of the cities that has experienced heat and humidity combinations past the threshold for human survival. Helen_In_UK / iStock / Getty Images Plus

For years, researchers have warned that the climate crisis could expose people around the world to a potentially deadly combination of heat and humidity later in the century.


Now, a new study published in Science Advances Friday shows that the conditions scientists thought were decades away are already here, and increasing.

"I was astonished by our findings," study coauthor Radley Horton of Columbia University told CNN. "My previously published study projected that these conditions would not take hold until later in the century. We may be at a closer tipping point than we think."

At stake is the human body's ability to withstand a certain combination of heat and humidity. When temperatures rise past 35 degrees Celsius, humans have to sweat to maintain their ideal body temperature, the study explained. But when it gets too humid, this is no longer possible. The combination of heat and humidity is calculated by something called the wet-bulb temperature, measured by wrapping a wet cloth around a thermometer and seeing how much it is cooled by evaporation, as EcoWatch explained previously. When humidity reaches 100 percent, the cloth has no effect. Wet-bulb temperatures of 35 or higher are too much for even healthy humans to survive outside for more than six hours, but wet-bulb temperatures much lower than that can still cause problems for human health. The deadly European and Russian heat waves of 2003 and 2010 respectively saw wet-bulb temperatures of only 28 degrees Celsius.

"It's hard to exaggerate the effects of anything that gets into the 30s," study coauthor Colin Raymond, a former Columbia Ph.D. student now at NASA's Jet Propulsion Laboratory, said in a Columbia University Earth Institute press release.

Previous observations had indicated that the 35 degree threshold had never been breached and that there had only been a few recordings of wet-bulb temperatures above 33 degrees, the study explained. But climate models had indicated that, without emissions reductions, such temperatures would be common later this century in parts of South Asia and the Middle East.

However, the latest research discovered that two weather stations had already recorded wet-bulb temperatures above 35 and several had seen temperatures higher than 31 and 33 degrees. In fact, since 1979, the number of wet-bulb temperatures above 30 degrees have doubled worldwide, CNN reported.

The study turned up such different results because it used a different method, as Scientific American explained. Previous studies had considered wider areas over several hours, but this study looked at data from more than 7,000 weather stations since 1979.

"[W]e decided to zoom in a little bit closer," Raymond told Scientific American.

The highest readings were recorded 14 times along the Persian Gulf, including in Doha, Qatar, where the 2022 FIFA World Cup is scheduled to take place, CNN reported. High wet-bulb temperatures were also recorded multiple times in India, Bangladesh, Pakistan, northwest Australia, the Red Sea coast and the Gulf of California in Mexico, according to the Earth Institute.

In the U.S., high temperatures were recorded dozens of times along the Gulf Coast. The worst-hit locations were New Orleans and Biloxi, Mississippi.

Extreme temperatures only occurred for an hour or two, Scientific American pointed out, meaning they are not yet at the level that automatically threatens human survival. However, heat waves are already the deadliest type of extreme weather event in the U.S., where it is relatively easier to shelter from high heat.

"This is not a problem for the end of the century, but in the present, especially in the developing world without widespread air conditioning," research meteorologist Ryan Maue, who was not involved with the study, told CNN.

And if temperatures rise to 2.5 degrees Celsius above pre-industrial levels, wet-bulb temperatures above 35 degrees would become common in parts of the world, the study found, according to Scientific American.

"[T]he inevitability of further increases is a sobering reminder of the importance of both mitigation of the temperature rise, and adaptation to what's already in store," Raymond wrote in a blog post

A net-casting ogre-faced spider. CBG Photography Group, Centre for Biodiversity Genomics / CC BY-SA 3.0

Just in time for Halloween, scientists at Cornell University have published some frightening research, especially if you're an insect!

The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.

"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."

The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.

They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.

They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.

But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.

"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.

What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.

It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.

To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.

First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.

Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.

University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.

"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."

Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.

Hoy agreed.

"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.

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