In Secret Test To Cool Earth, US Scientists Send Sunlight Back To Space

Scientists in the United States tried to bounce back some of the sun's rays into space as a way to temporarily cool Earth after the planet witnessed its hottest year on record in 2023, a report by the New York Times said.

They used cloud brightening, a technique that makes clouds brighter so that they reflect a small fraction of incoming sunlight and as a result, lower the temperatures of an area. If successful, the technology aims to position several devices aimed at the sky over oceans bringing down the rising sea temperatures.

A secret test on a decommissioned ship

On April 2, researchers at the University of Washington launched a mist of salt particles into the sky at a high speed from a snow-machine-like device placed atop a decommissioned aircraft carrier in San Francisco.

The experiment was performed under a secret project titled CAARE or Coastal Atmospheric Aerosol Research and Engagement.

The idea was to use clouds as mirror that reflect incoming sunlight, a concept explained by British physicist John Latham in 1990. He proposed to create a fleet of 1,000 ships that would travel across the globe spraying seawater droplets into the air to deflect solar heat and lower Earth's temperatures.

How does it work?

The idea behind the technology uses simple science: a large numbers of small droplets reflect more sunlight than small numbers of large droplets. Hence, spraying a mist of aerosol saltwater into the air could be used to bounce back sunlight.

But getting the size and amount of particles right is extremely crucial. If the particles are too small, they would not reflect and too big a particle will make clouds even less reflective.

For this test, scientists need particles that are 1/700th the thickness of a human hair and spray quadrillion such particles every second.

Can it fight global warming?

As countries around the world fail to meet the goal to keep temperatures at 1.5 degrees Celsius higher than preindustrial times, scientists are looking for novel solutions that could yield quick but significant results.

While some claimed the process can balance global warming caused by increased C02, several scientists think the results of the solar modification method would be hard to predict.

The excessive use of the technology, they say, could change climate patterns over time. For instance, changing ocean temperatures can alter marine biology and rain patterns increasing rainfall in one area while reducing it in another.