A new technique called Marine Cloud Brightening could be used to reflect sunlight and cool off the planet, according to Science Daily. The method is reversible but could give some relief to the warming Earth. The idea is to salt the clouds.
When water gathers on dust or other particulate in the air, clouds form. If the amount of salt particles were to increase, the clouds would become denser and more reflective, according to Science Daily.
The most effective way has been determined and published in the journal Philosophical Transactions of the Royal Society: "Rayleigh Jet."
Specially constructed ships could sail the world's oceans as they spray salt particles, which would remain in the atmosphere for a few days before returning as rain. The amount of energy needed for this feat was unknown until the recent report.
"There are many other factors that determine what the most efficient spray distribution is," wrote the study authors. "Here, we have merely focused on what we expect the most efficient spray parameters are for a given energy cost. However, factors such as energy availability; maintenance costs; engineering the apparatus to rapidly nebulize the sea spray; and factors that affect the transport of the spray into the cloud base, such as the effect of latent cooling on the buoyancy of the air, may all play an important role."
"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 School of Earth, Atmospheric and Environmental Sciences at the University of Manchester, according to Science Daily. "Our paper optimizes 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."
"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 continued, according to Science Daily. "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."
