The solution is to shoot salt into the sky to block the sun

A research group in the US has just tested cloud brightening technology using sea salt. The test will be the start of a promising technology that will help reduce global warming.

At 9 a.m., engineer Matthew Gallelli began work on the deck of a decommissioned aircraft carrier in the middle of San Francisco Bay, donning a pair of ear defenders and flipping a switch.

A few seconds later, a device that looked like a snowmaker began to rumble, followed by a loud, shrill screech. A fine mist filled with tiny salt particles shot out everywhere. These particles can fly up to tens of meters in the air.

This is the first outdoor test in the US for cloud brightening technology. This method makes clouds brighter and better reflects solar radiation back into space, thereby helping to cool the Earth and solve global warming, according to the New York Times.

Scientists at the University of Washington wanted to see if this machine, which took years to create, could spray microscopic salt particles outdoors, outside the laboratory. If successful, the next phase will target the sky and try to change the composition of clouds hovering over the ocean.

Originated from a crazy idea

Cloud brightening (also known as radiation management, solar geoengineering) is one of many ideas for pushing solar energy back into space. Compared to other options such as injecting gas into the stratosphere, the technique to brighten ocean clouds would be localized and use relatively benign sea salt aerosols instead of other chemicals.

The idea for this technology originated when British physicist John Latham published a study in the journal Nature, titled ' Controlling global warming?' in 1990. In his research, he proposed the idea that injecting microscopic particles into clouds could partly reduce rising temperatures.

Like airplanes, ships will push aerosol particles into the atmosphere to brighten clouds and reflect sunlight back into space. (Photo: Telegraph).

Then, while walking one afternoon with his son, Dr. Latham began to gain more inspiration for this idea. ' My son asked why the clouds were light at the top but dark at the bottom. I explained that they were mirrors that reflected sunlight,' he recalled.

Then, the doctor came up with a crazy proposal: create an army of 1,000 unmanned ships powered by sails, traveling through the world's oceans and continuously spraying microscopic drops of sea water into them. atmosphere, to deflect solar radiation away from Earth.

As ships move at sea, particles from their exhaust can brighten clouds, creating 'ship condensation contrails' behind them. In fact, the technique of enhancing marine clouds with ship tracks offsets about 5% of global warming due to greenhouse gases , said Dr. Doherty, an atmospheric scientist at the University of Washington and program manager. brighten ocean clouds - said.

Ironically, as better technology and environmental regulations have reduced the pollution emitted by ships, the cloud's brightness is fading, and temperatures are rising. According to Dr Doherty, instead of using pollutants, their marine cloud brightening program could be carried out using sea salt.

The ambitious project was supported by Bill Gates

In fact, increasing cloud brightness is not an easy task. Scientist Jessica Medrado - of the cloud brightening program at the University of Washington - said that to be successful, they had to achieve the exact size of the aerosols.

Particles that are too small will not be effective. Too large and they can be counterproductive, making the clouds less reflective than before. The ideal size is microscopic particles about 1/700th the thickness of a human hair.

Next, scientists need to push a lot of aerosols of that exact size into the air: One quadrillion particles per second. "You can't find any off-the-shelf tools ," Dr. Medrado says.

The answer to that problem comes from billionaire Bill Gates.

In 2006, the Microsoft founder heard the idea of ​​trying to reflect the Sun from David Keith, one of the leading researchers in solar geoengineering. Gates began funding Dr. Keith and Ken Caldeira, another climate scientist and former software developer, to continue their research.

Salt crystals shot into the air are microscopic in size, about 1/700th the thickness of a human hair. (Photo: New York Times).

The two scientists then met Armand Neukermans, a Silicon Valley engineer with a doctorate in applied physics from Stanford and 74 patents. He invented a system for producing and spraying ink particles for photocopiers. Dr. Caldeira asked if he could create a nozzle that sprayed not ink, but sea salt.

Intrigued by the idea, Dr. Neukermans recruited some of his former colleagues to research in a rented laboratory in 2009, with $300,000 investment from Bill Gates.

The team worked on this problem for years, eventually coming up with a solution. By pushing air at extremely high pressure through a series of nozzles, they can create enough force to smash salt crystals into microscopic particles.

By the end of last year, the salt sprayer was assembled and sitting in a warehouse near San Francisco. The machines are ready and now the team just needs somewhere to test them.

The next goal is to go to the big ocean

Finally, the Hornet aircraft carrier - a nationally recognized historical relic from World War II - became the place for the first test. The ship's deck is 15 meters above the shore of Alameda, San Francisco Bay. On the morning of April 3, the ship was filled with finely calibrated sensors, atop a scissor lift that rose straight into the air.

Below the American flag on the side is a salt fountain. It has a shiny blue color, roughly the shape and size of a spotlight cluster, and a ring of steel nozzles around the 1m-wide mouth. Researchers call it CARI (Cloud Injector Research Instrument).

The forklift's role is to hold sensors to measure the amount of salt sprayed from the machine during testing. (Photo: New York Times).

On one side of the sprayer is a box containing a pair of compressors, which supply high-pressure air to the sprayer through a thick, black hose. On the other side is a water tank. A series of switches are turned in sequence, which then introduces water and air into the device and shoots a fine mist toward the sensors.

The aim was to determine whether aerosols leaving the sprayer could maintain their size, as they rushed through the air under varying wind and humidity conditions. According to the New York Times, it will take scientists several months to analyze the results. But the answer will help determine whether ocean cloud brightening techniques are effective, said Dr. Robert Wood, principal scientist of the marine research group at the University of Washington.

She believes that scientists may need another decade of testing before officially using cloud brightening technology on a large scale to cool the Earth. "The next step is to go out to the ocean, aim the nozzle a little higher and touch the clouds ," the doctor told the New York Times.