Cloud brightening techniques can weaken El Nino

Theo CNNa new study by scientists at the Scripps Institution of Oceanography, USA, published on July 8 in the journal Science Advances, focuses on understanding whether solar geoengineering can reduce extreme heat, wildfires and other impacts of El Nino. They looked at marine cloud brightening (MCB), which sprays aerosols (tiny collections of solid particles or liquid droplets suspended in a gaseous environment) into clouds over the ocean to reflect sunlight away from Earth and back into space. Adding aerosols, especially sea salt particles, to the atmosphere can brighten the cloudiest areas of the ocean, making the clouds whiter, thereby increasing reflectivity and cooling the Earth.

The “Black Summer” forest fires in Australia in 2019 and 2020 burned tens of millions of hectares of land and killed hundreds of people. They also create smoke filled with particles that reflect sunlight, mixing with clouds over the Pacific Ocean. Previous research has found that these hyper-reflective clouds transmit a lot of solar energy back into space and cool the Pacific Ocean, contributing to the subsequent La Niña event.

Because it was impossible to conduct real-world geotechnical experiments to test the idea, the team simulated how MCB could mitigate the impact of El Nino. They focused on two strong El Niño events in 1997-1998 and 2015-2016, determined where the densest fly ash particles were in the southeast Pacific, and targeted that area for aerosol injection in computer simulations. Researchers found MCB could weaken the impact of El Nino, enhancing the cooling and drying effects associated with La Nina by 40%. They concluded that the earlier this technique was deployed during an El Nino event, the more effective it would be.

Theo Fox NewsEl Nino is part of a natural weather cycle called El Nino – Southern Oscillation (ENSO), which changes between warm and cold phases each 2-7 years apart. In the El Nino hot phase, warm water accumulates in the Pacific Ocean and spreads, causing the Earth’s average surface temperature to increase. El Nino usually lasts less than a year, but can cause great damage to people and property. Strong El Niño events in the past caused heat on land and oceans, heavy rains and flooding in some parts of the world while other areas suffered severe drought. According to Science NewsEarth entered an El Nino phase in June and computer simulations of current conditions in the Pacific show it has the potential to become a “super El Nino”.

Researchers admit that El Nino is a very complex phenomenon, causing trillions of dollars in damage to the global economy, but not all regions are negatively affected. Some places like California, USA, rely on the heavy rain that El Nino brings to replenish water reservoirs. The research team also emphasized the need to understand how MCB affects the time, frequency, intensity of the next La Nina event and the impact on each specific area.

Many researchers have reservations about meddling with the climate through geoengineering. “There are many open questions about the feasibility of MCB,” said James Haywood, a climate scientist at the University of Exeter in England. Previous research by Haywood and colleagues simulated the impact of MCB, finding that cooling of the eastern Pacific could create a super La Nina many times stronger than past events. In contrast to El Nino, La Nina typically brings cooler temperatures and milder weather but the impact is not uniform across the planet.