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Artificially altered clouds could help the Great Barrier Reef, experts say

Monday, September 13th 2021, 10:54 am - Marine cloud brightening, a speculative sector within the larger geoengineering approach, is being tested off the coast of Australia.

The Great Barrier Reef often appears in headlines when mass coral bleachings are detected, such as the memorable 2018 study that reported half of the reef had died since 2016. Many of us have become accustomed to these dire updates, but scientists say that there is reason to have hope.

A news feature published by Nature details the work that an Australian research team is doing to artificially alter clouds in hopes of blocking the reef from sunlight.

Researchers from Southern Cross University in Coffs Harbour are currently testing technologies that can be used to preserve the world's largest coral reef system. Daniel Harrison, an oceanographer and engineer, is leading a research project that is taking place on a repurposed ferry boat equipped with a mobile science laboratory.

Plume from sprayer jets with vessel 01 Cloud Brightening 2021 credit Brendan Kelaher SCU A plume from the vessel's sprayer jets. (Brendan Kelaher/SCU)

The boat sails 100 kilometres offshore and is then anchored so a cone-shaped turbine can generate a plume of seawater mist. The theory is that the brine droplets will evaporate and cool the plume as it floats across the ocean’s surface and eventually mixes upwards into low-lying clouds.

“Three-hundred and twenty nozzles spewed a cloud of nano-sized droplets engineered to brighten clouds and block sunlight — providing a bit of cooling shade for the coral colonies below. Scientists used sensors aboard the ferry, drones and a second boat to monitor the plume as it migrated skyward,” the news feature explains.

Plume from seawater sprayer 01 Cloud Brightening 2021 credit Brendan Kelaher SCU The seawater mist travelling across the ocean and slowly mixing up into the clouds. (Brendan Kelaher/SCU)

The researchers say that the cloud of seawater mist was not enough to significantly alter the clouds, but preliminary data indicates that their process could be capable of brightening clouds. “We are now very confident that we can get the particles up into the clouds. But we still need to figure out how the clouds will respond,” Harrison said.

The news feature says that Harrison’s research is the world’s first field trial of marine cloud brightening and is part of the Reef Restoration and Adaptation Program (RRAP), which received $6 million in funding from the Australian government in 2018. However, the news feature notes that Harrison’s experiment has received skepticism and criticism from climate scientists due to the limited amount of published research on the topic of marine cloud brightening.

Broadhurst Reef with research vessel 01 Cloud Brightening 2021 credit Brendan Kelaher SCU Broadhurst Reef with the research vessel in the distance. (Brendan Kelaher/SCU)

Marine cloud brightening gained support from RRAP because of the possibility that it could theoretically bring direct relief to specific regions of the coral reef system. This could be particularly useful during a localized heat wave that is severely affecting a vulnerable portion of the reef.

As reported by the news feature, Harrison stated that more experiments and modelling are needed to provide clarity around how much relief marine cloud brightening could bring to the Great Barrier Reef. While Harrison is confident in the future potential of this technology, he emphasizes the need for governments to limit greenhouse gas emissions.

“There are only so many clouds available, and there is only so much you can brighten them. Eventually, climate change just overwhelms things,” Harrison said.

Thumbnail credit: Alejandro Tagliafico/SCU

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