As fix for global warming, US scientists try 'sun blocking' to cool Earth

The scientists tested a technique that involves reflecting sunlight back into space in order to cool the Earth

The United States (US) has conducted the first outdoor test aimed at easing the effects of global warming, according to a report in the New York Times. On a decommissioned aircraft carrier in San Francisco Bay, engineer Matthew Gallelli conducted a test to evaluate a method designed to brighten clouds and reflect some of the sun's rays back into space, offering a temporary solution to cool the earth.

The Times report said the scientists wanted to check whether the machine could consistently spray the right size salt aerosols in open air, outside of a lab. If it works, the next step would entail trying to change the composition of clouds above the Earth’s oceans.

Through this experiment, the US scientists are trying to examine a possible way of "sun blocking", a method that involves reflecting sunlight back into space in order to cool the Earth. This strategy, known as solar radiation modification (SRM), has gained traction following a White House report indicating the US's openness to research its feasibility and effectiveness in combating climate change.

“Every year that we have new records of climate change, and record temperatures, heat waves, it’s driving the field to look at more alternatives,” said Robert Wood, the lead scientist for the team from the University of Washington that is running the marine cloud brightening project. “Even ones that may have once been relatively extreme," said Gallelli.

"Sun blocking" could reduce global temperatures by reflecting sunlight away from the Earth. One method involves stratospheric aerosol injection, where aircraft would disperse sun-blocking particles such as sulfur dioxide into the upper atmosphere. This method can create a reflective mist that would help in shielding the Earth from the rays of the sun. The potential of this method was proven when the eruption of Mount Pinatubo in 1991 led to a temporary global temperature decrease of 0.5 degree Celsius.

The UN Environmental Programme (UNEP) has concluded that, given current scientific understanding, "large-scale deployment of SRM technologies is not advisable". Andrea Hinwood, chief scientist at the UNEP, said that SRM cannot replace the need to reduce greenhouse gas emissions but didn't dismiss the possibility of revisiting this assessment should climate action remain insufficient.

David Santillo, a scientist with environment group Greenpeace International, expressed doubts about the feasibility of altering solar radiation to combat climate change. "You could well be changing climatic patterns, not just over the sea, but over land as well. This is a scary vision of the future that we should try and avoid at all costs," Santillo said.

Karen Orenstein, director of the climate and energy justice programme at Friends of the Earth U.S., a nonprofit environmental group, said that solar radiation modification is “an extraordinarily dangerous distraction”. She further said that the best way to address climate change would be to stop burning fossil fuels.