Scientists are patching clouds to save the Great Barrier Reef

It’s been a sweltering summer in Australia and corals on the Great Barrier Reef are showing early signs of stress.Authorities that manage the world’s largest coral reef system expect another bleaching event in the coming weeks — if that happens, it would be the sixth time since 1998 that a surge in water temperatures has wiped out large swathes of coral that inhabit countless sea creatures.animal.Three of these bleaching events that make corals more susceptible to disease and death have occurred in the past six years alone.When corals experience extreme and prolonged heat stress, they expel the algae living in their tissues and turn completely white.This could have devastating effects on thousands of species of fish, crabs and other marine species that rely on coral reefs for shelter and food.To slow the rate of coral bleaching caused by ocean warming, some scientists are looking to the sky for a solution.Specifically, they are looking at the cloud.
Clouds bring more than just rain or snow.During the day, the clouds act like giant parasols, reflecting some of the sunlight from Earth back into space.Marine stratocumulus clouds are especially important: they are located at low altitudes, thick and cover about 20 percent of the tropical ocean, cooling the water below.That’s why scientists are exploring whether their physical properties can be altered to block more sunlight.On the Great Barrier Reef, it is hoped that some much-needed relief will be provided to coral colonies amid increasingly frequent heatwaves.But there are also projects aimed at global cooling that are more controversial.
The idea behind the concept is simple: shoot large amounts of aerosols into the clouds above the ocean to increase their reflectivity.Scientists have known for decades that particles in pollution trails left by ships, which look a lot like trails behind planes, can illuminate existing clouds.That’s because these particles create the seeds for cloud droplets; the more and smaller the cloud droplets, the whiter and better the cloud’s ability to reflect sunlight before it hits and heats the Earth.
Of course, shooting aerosols of pollutants into clouds is not the right technology to solve the problem of global warming.The late British physicist John Latham had proposed in 1990 to use salt crystals from evaporating seawater instead.The sea is plentiful, mild, and especially free.His colleague Stephen Salter, professor emeritus of engineering and design at the University of Edinburgh, then suggested deploying a fleet of around 1,500 remote-controlled boats that would sail the oceans, sucking water and spraying fine mist into the clouds to make the clouds brighter.As greenhouse gas emissions continue to rise, so does interest in Latham and Salter’s unusual proposal.Since 2006, the pair have been collaborating with about 20 experts from the University of Washington, PARC and other institutions as part of the Oceanic Cloud Brightening Project (MCBP).The project team is now investigating whether deliberately adding sea salt to the low, fluffy stratocumulus clouds above the ocean would have a cooling effect on the planet.
Clouds appear to be particularly prone to brightening along the west coast of North and South America and central and southern Africa, said Sarah Doherty, an atmospheric scientist at the University of Washington in Seattle who has managed MCBP since 2018.Clouds Water droplets do form naturally on oceans when moisture collects around salt grains, but adding a little salt to them can increase the reflective power of clouds.Brightening the large cloud cover over these suitable areas by 5% could cool much of the world, Doherty said.At least that’s what computer simulations suggest.”Our field studies of jetting sea salt particles into clouds on a very small scale will help to gain a deeper understanding of key physical processes that can lead to improved models,” she said.Small-scale experiments of the prototype device were scheduled to begin in 2016 at a site near Monterey Bay, California, but they have been delayed due to a lack of funding and public opposition to the experiment’s possible environmental impact.
“We’re not directly testing ocean cloud brightening of any scale that affects climate,” Doherty said.However, critics, including environmental groups and advocacy groups such as the Carnegie Climate Governance Initiative, worry that even a small experiment could inadvertently affect the global climate due to its complex nature.”The idea that you can do this on a regional scale and on a very limited scale is almost a fallacy, because the atmosphere and ocean have been importing heat from elsewhere,” said Ray Pierre Humbert, professor of physics at the University of Oxford.There are also technical challenges.Developing a sprayer that can reliably brighten clouds is no easy task, as seawater tends to clog as salt builds up.To address this challenge, MCBP enlisted the help of Armand Neukermans, the inventor of the original inkjet printer, who worked at Hewlett-Packard and Xerox until his retirement.With financial backing from Bill Gates and other tech industry veterans, Neukmans is now designing nozzles that can blast saltwater droplets of the right size (120 to 400 nanometers in diameter) into the atmosphere.
As the MCBP team prepares for outdoor testing, a team of Australian scientists has modified an early prototype of the MCBP nozzle and tested it over the Great Barrier Reef.Australia has experienced a 1.4°C warming since 1910, exceeding the global average of 1.1°C, and the Great Barrier Reef has lost more than half of its corals due to ocean warming.
Cloud brightening can provide some support for reefs and their inhabitants.To achieve this, Southern Cross University engineering oceanographer Daniel Harrison and his team fitted a research vessel with turbines to pump water out of the ocean.Similar to a snow cannon, the turbine extracts water and blasts trillions of tiny droplets into the air through its 320 nozzles.The droplets dry in the air, leaving behind salty brine, which theoretically mixes with low-level stratocumulus clouds.
The team’s proof-of-concept experiments in March 2020 and 2021 — when corals are most at risk of bleaching at the end of the Australian summer — were too small to significantly alter cloud cover.Still, Harrison was surprised by the speed with which the salty smoke drifted into the sky.His team flew drones equipped with lidar instruments up to 500 meters high to map the motion of the plume.This year, a plane will cover the remaining few meters to assess any reaction in clouds over 500 meters.
The team will also use air samplers on a second research vessel and weather stations on coral reefs and ashore to study how particles and clouds naturally mix to improve their models.”Then we can start looking at how cloud brightening, if done on a larger scale, might affect the ocean in desirable and unexpected ways,” Harrison said.
According to the modelling done by Harrison’s team, reducing the light above the reef by about 6% would reduce the temperature of the reefs on the middle shelf of the Great Barrier Reef by the equivalent of 0.6°C.Scaling up the technology to cover all reefs—the Great Barrier Reef is made up of more than 2,900 individual reefs spanning 2,300 kilometers across—will be a logistical challenge, Harrison said, as it would require about 800 spray stations to run for months before expected high waves.The Great Barrier Reef is so large that it can be seen from space, but it covers only 0.07% of the Earth’s surface.Harrison acknowledged that there are potential risks to this new approach that need to be better understood.Cloud brightening, which can disrupt clouds or alter local weather and rainfall patterns, is also a major concern with cloud seeding.It’s a technique that involves planes or drones adding electrical charges or chemicals like silver iodide to clouds to produce rain.The United Arab Emirates and China have experimented with the technology to tackle heat or air pollution.But such measures are hugely controversial – many consider them very dangerous.Cloud seeding and brightening are among so-called “geoengineering” interventions.Critics say it’s too risky or a distraction from reducing emissions.
In 2015, physicist Pierrehumbert co-authored a National Research Council report on climate intervention, warning of political and governance issues.But a new report from the academy, released in March 2021, took a more supportive stance on geoengineering and recommended that the U.S. government invest $200 million in research.Pierrehumbert welcomed the ocean cloud brightening research but found problems with the spray equipment developed as part of an ongoing research project.The technology could get out of hand, he said.”Scientists who say it’s not a substitute for emissions control, they’re not going to be the ones making the decisions.” Australian government heavily criticized for inaction to tackle climate crisis and its reliance on coal-fired power generation, sees ocean clouds brightening potential.In April 2020, it launched a $300 million program to restore the Great Barrier Reef in April 2020 – this funding has funded research, technology development and testing of more than 30 interventions, including ocean cloud brightening .Although the massive investment measures such as Yun Zengliang are still controversial.Environmental groups argue this could pose ecological risks and distract from efforts to limit greenhouse gas emissions.
But even if cloud brightening proves effective, Harrison doesn’t think it will be a long-term solution to saving the Great Barrier Reef.”Brightening clouds can only bring limited cooling,” he said, and with the climate crisis likely to worsen, the effects of any brightening will soon be overcome.Instead, Harrison argues, the aim is to buy time while countries lower their emissions.”It’s too late to hope that we can quickly reduce emissions to save coral reefs without any intervention.”
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