Cloud-based sunscreen could help protect the Great Barrier Reef from future heat damage

Scientists in Australia have started testing a radical idea to brighten clouds over the Great Barrier reef to protect it from future heat damage.

They hope to enhance low-lying marine clouds over the reef to make them reflective so they bounce more of the sun's energy away from Earth to cool the water.

Every droplet in a cloud needs a tiny particle to condense around, and the brightness in clouds is determined by the size and number of those droplets. 

Marine cloud brightening works by spraying tiny particles of seawater into the air that evaporate, leaving behind salt crystals that act like seeds for water vapour to condense around.

Daniel Harrison, a senior lecturer at the National Institute of Marine Science at Southern Cross University in Australia, led experiments that he said would produce a localized effect over the Great Barrier Reef.

Their goal of those experiments was to test nozzles that were engineered to spray micron-sized droplets of seawater into the air to see how the plume of salt crystals that evaporate out of the droplets behaved.

Harrison told Quirks & Quarks host Bob McDonald they were encouraged by their results that suggest the particles that evaporated out of the tiny droplets of seawater did make it up the clouds, even if they were only spraying a tenth of the mist that'd be required to actually brighten the clouds.

He said their current calculations suggest it would take 800 stations spraying a fine mist of seawater during extreme heat waves to protect the reef recover, but that's only if we also reduce emissions. If not, then, he said this method could help for a couple of decades, but the reef would still collapse.

Produced and written by Sonya Buyting. Click on the link at the top of the page to hear the interview with Daniel Harrison.