British researchers have identified the cheapest geoengineering method to increase brightness of clouds to make them reflect more sunlight thus reducing warming of the Earth.
Comparing various previously developed marine cloud-brightening methods, the study found that a technique known as the Rayleigh Jet provides a 5 per cent reflection increase while consuming only 30 megawatts of energy.
This 5 per cent, the researchers believe, would be enough to balance out the effects of rising carbon dioxide concentrations in the atmosphere for the rest of the century.
The Rayleigh jet relies on injecting a fine mist of salt particles into the atmosphere to increase the amount of sunlight the clouds reflect back to space.
“It can be incredibly energy intensive to propel water high into the atmosphere and the energy required had never really been tested before,” said Paul Connolly from the University of Manchester, a lead author of the study published in the latest issue of the Royal Society’s journal Philosophical Transactions.
“Our paper optimises the salt particle sizes to produce the required change in cloud reflectance for the least energy cost. It is an important finding if these techniques should be needed in the future.”
According to Lord Rayleigh, the scientist who formed the Rayleigh jet theory, the reflectivity of clouds could be increased by spraying salt water into the sky from specially built ships that could crisscross the world’s oceans to achieve even coverage.
The water injected into the atmosphere would quickly evaporate leaving behind only the salt particles that would serve as additional condensation nuclei, making the clouds denser and thus more reflective.
Previous studies have optimised the size of the salt particles needed to produce the best increase in cloud reflectance but haven’t taken into account how much energy the technique would need and how much it would cost.
The paper, a collaboration between the universities of Manchester, Washington and Edinburgh, comes at a time when the global climate community is becoming increasingly certain that barely reducing greenhouse gas emissions by developing renewable resources might not be enough to ward off the consequences of global warming.
A UN body recommended last month that governmental support of carbon capture storage technologies should be embedded into the new climate change treaty to be negotiated next year in Paris. Slowly, other, more daring geoengineering concepts are moving from the science-fiction realm to possible necessity.
“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,” Connolly said. “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.”