Scientists: Cloud geoengineering could save our climate

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A controversial idea is becoming popular amongst some scientists, hoping to reverse the effects of global warming. The idea consists of futuristic ships to shoot salt water high into the sky over the oceans. The process would create clouds that reflect sunlight and combat global warming. Although it may sound like a wacky endeavour only found in sci-fi flicks, some researchers are taking a more serious look at the concept of geoengineering.

Rob Wood is an atmospheric physicist at the University of Washington. In the journal ‘Philosophical Transactions of the Royal Society’, he describes a possible way to run an experiment to test the concept on a smaller scale.

The paper includes updates on the latest study into what kind of ship would be best to spray the salt water into the sky, how large the water droplets should be and the potential climatological impacts. It is meant to encourage more scientists to consider the idea of marine cloud brightening.

Wood and his colleague detail an experiment to test the concept.

“What we’re trying to do is make the case that this is a beneficial experiment to do. With enough interest in cloud brightening from the scientific community, funding for an experiment may become possible,” Wood said.

The theory behind so-called marine cloud brightening is that adding sea salt to the sky over the ocean would form large, long-lived clouds. Clouds appear when water forms around particles. Since there is a limited amount of water in the air, adding more particles creates more, but smaller, droplets.

“It turns out that a greater number of smaller drops has a greater surface area, so it means the clouds reflect a greater amount of light back into space,” Wood said. This would ultimately create a cooling effect on Earth.

Marine cloud brightening is just a small facet of the larger concept known as geoengineering. The study involves efforts to use technology to manipulate the environment.

Brightening, like other geoengineering proposals, is controversial for its ethical and political effects and the uncertainty around its impact. But Wood says those aren’t reasons not to study it.

In the report, Wood and his colleague say the test should start by deploying sprayers on a ship to ensure that they can inject enough particles of the targeted size to the appropriate elevation. An airplane equipped with sensors would study the physical and chemical characteristics of the particles and how they disperse. The next step would be to use additional airplanes to study how the cloud develops and how long it remains. The final phase of the experiment would send out five to 10 ships, spread out across a 100 kilometre stretch. The resulting clouds would be large enough so that scientists could use satellites to examine them and their ability to reflect light.

In the field of climate science, researchers observe rather than try to change the atmosphere. That’s why an experiment like this is so unusual.

Reports say ship trails is a phenomenon that inspired marine cloud brightening. Ship trails are clouds that form behind the paths of ships crossing the ocean, similar to the trails that airplanes leave across the sky. Ship trails form around particles released from burning fuel.

Despite increasing interest from scientists like Wood, there is still strong resistance to cloud brightening. That’s why the authors of the paper say they are treading cautiously.

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