This week's short read: Marine Cloud Brightening and Cool Fabrics, and Elephants

[SteamyTea]

 

Cloud geoengineering could push heatwaves from US to Europe

Climate models suggest that a possible scheme to cool the western US by making clouds brighter could work under current conditions, but may have severe unintended consequences in a future scenario

By James Woodford

21 June 2024

 

 

 

Brightening clouds over the Pacific Ocean could help to cool the western US

Stocktrek/Alamy

 

A cloud-modifying technique could help cool the western US, but it would eventually lose its effectiveness and, by 2050, could end up driving heatwaves around the planet towards Europe, according to a modelling study.

There is growing interest in alleviating the severe impacts of global warming by using various geoengineering techniques. These include marine cloud brightening (MCB), which aims to reflect more sunlight away from Earth’s surface by seeding the lower atmosphere with sea salt particles to form brighter marine stratocumulus clouds.

Small-scale MCB experiments have already taken place in Australia on the Great Barrier Reef and in San Francisco Bay, California. Proponents hope this approach could be used to reduce the intensity of extreme heatwaves in particular regions as the climate continues to get hotter.

Katharine Ricke at the University of California, San Diego (UCSD), and her colleagues modelled the impact that a possible MCB programme to cool the western US might have under present climate conditions and projections for 2050.

The team modelled the impact of MCB in two locations in the northern Pacific Ocean: one in temperate latitudes and another in sub-tropical waters. The modelling applied MCB for 9 months out of every year for 30 years, essentially altering the long-term climate.

The researchers found that under present-day climate conditions, MCB reduces the relative risk of dangerous summer heat exposure in parts of the western US by as much as 55 per cent. However, it dramatically reduces rainfall, both in the western US and in other parts of the world such as the Sahel of Africa.

They also modelled the impact MCB would have in 2050, in a predicted scenario where global warming reaches 2°C above pre-industrial temperatures. Under these conditions, the same MCB programme was ineffective and instead dramatically warmed almost the entirety of Europe, except the Iberian peninsula. Ricke says the modelled temperature increase was especially large in Scandinavia, Central Europe and Eastern Europe.

These far-reaching impacts were caused by changes to large-scale atmospheric currents leading to unexpected consequences.

Team member Jessica Wan at UCSD says a big takeaway is that the impacts of regional MCB aren’t always intuitive. “Our results provide an interesting case study illustrating the unexpected complexities in the climate system you can uncover through regional geoengineering because of the highly concentrated perturbation to a small part of the planet.”

The MCB experiments that have taken place so far in Australia and California haven’t been of a sufficiently large scale to cause detectable climate effects, but they suggest that regional geoengineering could be closer to reality than previously thought, says Wan. “We need more regional geoengineering modelling studies like this work to characterise these unintended side effects before they have a chance to play out in the real world.”

Ricke says another issue is that if countries start to rely on these methods while they are still effective, it may discourage action to reduce carbon emissions. Then, when the geoengineering stops working, the world would be locked into an even more dangerous trajectory, she says.

“Lock-in is a major concern people have about geoengineering approaches in general because there will be opportunity costs associated with pursuing these approaches,” says Ricke. “In a world like the one we simulate, what other risk management approaches would we have invested in developing if we hadn’t pursued MCB?”

Daniel Harrison at Southern Cross University in Australia is the project lead of the research looking into whether MCB could be used in the future as a tool to mitigate heatwaves in the Great Barrier Reef region.

He says the scenarios modelled by the new paper’s authors are “completely unrealistic and extreme”. “It’s a huge poke to the global climate system, so of course there will be consequences,” he says.

The project Harrison is researching would involve MCB over much shorter time periods and in a fraction of the area modelled by Ricke’s team, he says.

John Moore at the University of Lapland in Finland says there is an urgent need for more research on solar geoengineering to explore the possible outcomes more thoroughly, including the impact on low-income countries and Indigenous peoples in the Arctic.

 

Journal reference:

Nature Climate Change DOI: 10.1038/s41558-024-02046-7

 

 

Cooling fabric blocks heat from pavement and buildings in hot cities

A three-layered textile made from fabric, plastic and silver nanowires can keep a person several degrees cooler than silk or other cooling materials

By James Dinneen

13 June 2024

 

 

 

A scorching day in Bucharest, Romania in June 2019

lcv / Alamy

 

Future city dwellers could beat the heat with clothes made of a new fabric that keeps them cool.

The textile, made of a plastic material and silver nanowires, is designed to stay cool in urban settings by taking advantage of a principle known as radiative cooling – the natural process by which objects radiate heat into space.

The material selectively emits infrared radiation within the narrow band of wavelengths that can escape Earth’s atmosphere. At the same time, it blocks the sun’s radiation and infrared radiation emitted by surrounding structures.

Po-Chun Hsu at the University of Chicago in Illinois and his team designed this material to “try to block more than half of [the radiation] from the buildings and the ground”, he says.

Some cooling fabrics and building materials already rely on this radiative cooling principle, but most of those designs do not account for radiation from the sun or infrared radiation from structures like buildings and pavement. They also assume the material would be oriented horizontally to the sky like panels on a rooftop, rather than the vertical orientation of material in clothes worn by a person.

Those designs work well “when you are facing a cooler object such as the sky or an open field”, says Hsu. “However, that’s rarely the case when you are facing an urban heat island.”

Hsu and his colleagues designed a three-layer textile. The inner layer is made of a common clothing fabric like wool or cotton, and the middle layer consists of silver nanowires that reflect most radiation.

The top layer is made of a plastic material called polymethylpentene, which doesn’t absorb or reflect most wavelengths, but emits a narrow band of infrared radiation.

In outdoor tests, the textile stayed 8.9°C (16°F) cooler than a regular silk fabric and 2.3°C (4.1°F) cooler than a material that emitted radiation across a broad range. When tested on skin, the textile was 1.8°C (3.2°F) cooler than a cotton fabric.

Hsu says this small difference in temperature could theoretically increase the time someone could comfortably be exposed to heat by up to a third, although this hasn’t yet been tested.

“Making this stuff practical as a textile is always difficult,” says Aaswath Raman at the University of California, Los Angeles, adding the work is a good demonstration of translating the physical principle of radiative cooling to a usable material. Other materials with similar properties could also be used on the vertical surfaces of buildings, he says.

 

Journal reference

Science DOI: 10.1126/science.adl0653

 

Elephants seem to invent names for each other

An analysis of their vocalisations suggests that African savannah elephants invent names for each other, making them the only animals other than humans thought to do so

By Michael Le Page

10 June 2024

 

 

 

Two juvenile elephants greet each other in Samburu National Reserve in Kenya

George Wittemyer

 

Elephants may be the only animals besides humans to come up with arbitrary names for each other, according to an analysis of recordings using machine learning.

The analysis found that some calls from African savannah elephants (Loxodonta africana) seem to contain name-like components specific to certain individuals. What’s more, those individuals know their names, responding more strongly than others do when calls addressed to them are played back on a speaker.

 

 

 

“I had noticed from years back that when an elephant gave a contact rumble, within a group of elephants I would see one individual lift its head, listen and give an answer,” says Joyce Poole at ElephantVoices, a small organisation that studies elephants and aims to protect them. “And the rest seemed to just ignore the elephant. So I did wonder whether the calls were being directed toward a specific individual.”

More than 600 recordings made by Poole and others have now been analysed by Michael Pardo at Colorado State University and his colleagues. The recordings included contact rumbles, made when the recipient is out of sight, and greeting rumbles, made when one elephant approaches another. The researchers knew which individuals were calling and responding in each case.

In a quarter of cases, the software created by the team was able to predict which individual was being addressed, a result significantly better than chance.

The researchers then played back some of the rumbles to pairs of elephants, including the “named” individual. They found that the named elephant responded more strongly: they approached the speaker faster, made calls in response faster and also made more calls altogether than the other individual that wasn’t addressed by name.

Dolphins and several species of birds have been shown to call to specific individuals by imitating the sound made by the animal they are calling. However, while Poole reported in 2005 that elephants can learn to mimic sounds, the team found no evidence that the elephants were mimicking each other.

In other words, they seem to be using arbitrary sounds as names, just as humans do, says Poole.

What the analysis didn’t reveal is whether different elephants share the same name for one specific individual. It could be that each elephant has its own set of names for others.

“With us, we have formal names, but different individuals may refer to the same person with different nicknames,” says Poole. “So it may be something like that. I don’t think we know yet.”

“This is a super interesting study with multiple lines of evidence suggesting that African elephants not only produce individually specific vocalisations – which is commonly reported in many species – but more importantly respond specifically when they hear their own individually specific vocalisation given by another elephant,” says Daniel Blumstein at the University of California, Los Angeles.

“The idea that elephants can use individually specific vocalisations to attract specific individuals is novel, exciting and opens the door to a much more nuanced understanding of the rich social lives that these animals have,” he says.

“I find the results quite plausible,” says Thorsten Balsby at Aarhus University in Denmark.

Balsby studies parrots that live in much larger groups. He points out that in large populations with hundreds or thousands of individuals, learning names would be very difficult. “Addressing other individuals by imitation is a simpler solution that does not require prior interactions,” he says.

A 2005 study reported that green-rumped parrotlets kept in captivity “vocally labelled”, or named, their companions, says Balsby. But they did so with different versions of their contact call. “So it might not be quite as arbitrary as the elephants,” he says.

Poole thinks her study is just the beginning when it comes to understanding elephant communication. “There are layers of complexity in elephant communication that are going to take some time to unravel, so I think we’ll have lots more exciting discoveries in the years to come,” she says.

For instance, she suspects elephants might use place names too. “When they’re giving their ‘let’s go’ rumbles, where they indicate the direction they want to go to other individuals in the group, they might actually be saying precisely where they want to go,” says Poole.

 

Journal reference:

Nature Ecology & Evolution DOI: 10.1038/s41559-024-02420-w