Updated: Wednesday, 19th June 2019 @ 12:38pm

Tackle global warming by 'firing salt into atmosphere from boat to brighten clouds', says Manchester scientist

Tackle global warming by 'firing salt into atmosphere from boat to brighten clouds', says Manchester scientist

| By Aidan Gregory

Global warming could be tackled by propelling salt particles into the atmosphere from ships – in a bid to ‘brighten clouds’ to reflect the sun’s rays, according to Manchester scientists.

The method, known as Marine-Cloud Brightening, has been designed to reduce rising global temperatures by boosting the reflectivity of the atmosphere.

Increasing the amount of salt particles in the atmosphere causes clouds to develop greater water density, and therefore become more resistant to sunlight. 

If proven effective, it could reduce the number of dangerous UV rays that reach the earth’s surface.

Dr Paul Connolly, from the School of Earth, Atmospheric and Environmental Sciences at the University of Manchester, told MM: “This whole idea of Marine Cloud Brightening is controversial because it has ethical and political ramifications, and there’s a lot of uncertainty about whether it will work.

“But it’s quite an interesting thing to look at anyway. I’d rather have it that scientists test the idea rather than groups that have a vested interest, because if you’re making money from it, then the assumption is that it’s going to work.”

In a paper published in the journal Philosophical Transactions of the Royal Society A, and co-authored by scientists from the universities of Manchester, Edinburgh, and Washington, the scientists examined four different methods of getting the particles up into the sky, to determine their energy-efficiency.

They concluded that most energy efficient method would be to use specifically designed ships that would travel the world spraying salt water up into the sky – a method known as the Raleigh Jet Method (RJM), after its creator Lord Raleigh.

The paper also argues that the RJM could achieve its aim using just 30 megawatts of energy – which is the equivalent to the energy produced by two large ships.

Of the four methods, the RJM is the only one that remains untested.

Dr Connolly said: “The Rayleigh Jet idea has not even been built yet, but there are plans. [With] the other methods, prototypes have been built, and spray has been generated into quite large rooms.”

However there are concerns about how much the method will cost should it ever be used.

“We started to look at this [In the paper], when we said how much energy it would take,” said Dr Connolly.

“We had all these figures and we started to look at how much it would cost if you were to implement all of this. You’re looking at money to build the ships, money to maintain the ships.

“The next step is to do a cost-benefit analysis to see whether it’s worth doing in the first place, even if it works as planned. It could be cost effective.”

He explained that it is highly energy intensive to propel water high into the atmosphere, though it has not been tested before, so exactly how much is not known.

“Our paper optimises the salt particle sizes to produce the required change in cloud reflectance for the least energy cost,” he said.

“It is an important finding if these techniques should be needed in the future.

“I am not recommending that we use any of these techniques now, but it is important to know how best to use them should they become necessary.

"Should no progress be made to reduce CO2 levels, then geoengineering techniques, similar to this, might become necessary to avoid dangerous rises in global temperatures.”

Image courtesy of Michael Taggart Photography, with thanks.