US scientists try new method to repel Sun’s rays: Will this help cool the Earth?

2023 was the hottest year on record.

Scientists are searching for innovative solutions that could produce noticeable effects quickly, as many nations are failing to maintain global temperatures at 1.5 degrees Celsius above preindustrial levels.

In the same vein, American scientists have tried to bounce back some of the sun’s rays into space as a way to temporarily cool Earth.

According to a New York Times report, they carried out the first outdoor test in San Francisco Bay to reduce the effects of global warming.

Let’s take a closer look.

The experiment

On 2 April, University of Washington researchers utilised a snow-machine-like device atop a decommissioned aircraft ship in San Francisco Bay to discharge a mist of salt aerosols into the open at a high speed.

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The study was carried out as part of a secret initiative called Coastal Atmospheric Aerosol Research and Engagement, or CAARE.

In 1990, British physicist John Latham outlined the idea of using clouds as mirrors that reflect incoming sunlight in a paper titled Control of Global Warming? that was published in the journal Nature.

To block solar heat and cool Earth, he suggested building a fleet of 1,000 ships that would sail the entire planet while shooting seawater droplets into the atmosphere.

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The method called cloud brightening, also called solar radiation modification or solar geoengineering, is used to push solar energy back into space.

It brightens clouds, causing them to reflect a tiny amount of incoming sunlight and lowering local temperatures.

Put simply, more sunlight is reflected by many little droplets than by few large droplets. Therefore, it might be possible to bounce sunlight back into space by misting aerosol saltwater into the atmosphere.

However, it’s crucial to get the particle size and quantity exactly right.

Particles that are too large will make clouds even less reflecting, while particles that are too small will cause clouds to not reflect at all.

In order to do this test, scientists must spray quadrillion of these particles each second, with each particle being 1/700th the thickness of a human hair.

If the technology works, it will place many devices above oceans with their faces directed towards the sky in an attempt to reduce the rising sea temperatures.

Cloud brightening already exists

Sarah Doherty, an atmospheric scientist at the University of Washington and the manager of its marine cloud brightening programme, claims that daily instances of marine cloud brightening already occur. Ship tracks are the brightened clouds left behind by the exhaust particles from ships as they sail the oceans, according to The New York Times.

According to her, until recently, the brightening of the clouds caused by ship tracks neutralised about five per cent of the heat caused by greenhouse gases.

Strangely, the unintentional cloud brightening and accompanying cooling are diminishing as environmental rules and improved technology have decreased the pollution that ships release.

Rather than using pollution, Dr Doherty suggested using sea salts as part of a purposeful programme to brighten marine clouds.

She told the outlet that there were potential side effects that still needed to be studied.

Another way that cloud brightening might change precipitation patterns is by decreasing rainfall in some areas and increasing it in others.

She maintained, however, that in the case that society requires such technologies, it is essential to determine their viability and mechanism.

Experts’ opinion

While some suggested the procedure may counteract the warming brought on by rising CO2, other scientists believe it would be difficult to foresee the effects of the solar modification method.

Senior scientist David Santillo of Greenpeace International stated that it would be difficult to gauge, let alone foresee, the effects of using marine cloud brightening on a scale that may cool the planet.

He told NYT, “You could well be changing climatic patterns, not just over the sea, but over land as well,” he said. “This is a scary vision of the future that we should try and avoid at all costs.”

Karen Orenstein, director of the Climate and Energy Justice Program at Friends of the Earth U.S., a non-profit environmental group, called solar radiation modification “an extraordinarily dangerous distraction.”

She said that switching away from the use of fossil fuels would be the best course of action to combat climate change.

Global warming 

Last year former NASA top climate scientist James Hansen and others published a study saying the climate is not just getting warmer, but the rate of change is accelerating.

A second study found ocean heat content, where much of Earth’s trapped energy is stored, is rising at a faster rate than before.

“One of the most direct consequences of global warming is increasing heat waves,” Woodwell Climate Research Center scientist Jennifer Francis told The Associated Press.

Climate change is making giant heat waves crawl slower across the globe and they are baking more people for a longer time with higher temperatures over larger areas, a new study has found.

The study also looks at the changes in weather patterns that propagate heat waves. Atmospheric waves that move weather systems along, such as the jet stream, are weakening, so they are not moving heat waves along as quickly — west to east in most but not all continents.

With inputs from agencies