'Cloud brightening' experiment may help cool Great Barrier Reef

Researchers trying to save the are attempting to cool the unusually warm sea temperatures using “cloud brightening”, a geoengineering technique designed to reflect more of the sun’s rays away from the Earth.

The team are spraying microscopic seawater droplets into the air over the reef, which creates more cloud cover and more shade in an effort to save the health of one of the world’s most important marine ecosystems.

In the last few weeks, and for the third time in five years, the reef has suffered a mass bleaching event where stress from unusually warm water temperatures bleach the coral white and can kill it.

February was the warmest month on record in terms of water temperatures around the reef, with readings in some places of more than 3ºC above average for the time of year.

“If we can brighten the clouds just a little bit over the whole summer, then we can cool down the water enough to stop some of the coral bleaching,”  project leader and Southern Cross University senior lecturer Dr Daniel Harrison said.

Just before the coronavirus lockdown, the researchers deployed two boats to a site over the Great Barrier Reef, 100km west of Townsville, but without the international researchers who had planned to join them.

They tested a prototype turbine to atomise seawater and blow it into the air, with a drone in the atmosphere and a sampling vessel 5km away.

The droplets evaporate leaving tiny salt crystals which float up into the atmosphere, allowing water vapour to condense around them and form clouds.

In 2021, the team plans to test the technology at three times the size, ready for a tenfold increase a year later, which the researchers say should be able to brighten clouds across a 20x20-kilometre area — Reuters