CAJ - Albedo enhancement (Clouds)

Albedo enhancement

As I have mentioned in my plans before I would like to present all the Geoengineering techniques more in depth. To discuss the more controversial techniques in the beginning, I would like to start with SRM methods.

Albedo enhancement, also called cloud reflectivity modification or marine cloud brightening, is a proposed Geoengineering method to reflect sunlight back into space. In combination with greenhouse gas emissions reduction, the albedo enhancement could create a considerable global cooling effect. Scientists aim to primarily modify marine stratocumulus clouds (SC) since they tend to be warm and significantly reflect incoming solar radiation back to space, especially when they are white. Enhancing the albedo of marine stratocumulus clouds could be done via cloud condensation nuclei (CCN) which increases the cloud droplet number concentration and the cloud albedo and thus make them appear whiter. Even the clouds' longevity could potentially be enhanced without changing their natural precipitation. It has been estimated by several researches, most prominently John Latham and Stephen Salter, that a 4% increase in the cloud areal coverage or, on the other hand, only a 0.06 increase in the cloud albedo of marine SC can stabilise the warming in the atmosphere which is caused by CO2 emissions. This could have a huge effect on the Earth’s atmosphere system considering that SC cover vast areas of the ocean surface, one-third to be precise. In fact, injecting these chemicals is more effective over the ocean than over land since levels of dust and pollution at sea has resulted in a deficit of CCN.

Ways to do so:

There are several ways and schemes proposed for this Geoengineering technique. One suggested scheme is to spray seawater into the atmosphere and as a result increase the albedo of clouds. Sea-salt climate engineering (SSCE) might be the most plausible and feasible possibility of all. Specially designed unmanned boats would plow the seas, spraying salt water into the air. The water would evaporate and leave behind sea-salt particles which could be lifted into the clouds and therefore increase their albedo. The created CCN by the spray will change the distribution of the droplets in already existing clouds to make them appear whiter.

The leading scientist Salter, a professor at the University of Edinburgh, has proposed a scheme that aims to deploy remote-controlled, unmanned, wind-powered vessels which are capable of generating (via turbines dragged through the water) the electricity required to create a mist of seawater and injecting the droplets 1,000 meters into the atmosphere. This scheme could even reverse a doubling  of CO2 in the future. 

 

Another model developed by Salter includes an unmanned yacht and Flettner rotors, which are perpendicular rotating cylinders to the direction of the airstream for propulsion. These cylinders would be placed on the deck of the yacht spraying the sea water droplets into the SC to enhance their albedo and thus their reflectivity. Underwater turbines would act as power sources for the rotors and the ship. 1,500 of ships like these would be required for this scheme to have a significant effect on the planet’s climate. However, this techniques  requires far less energy compared to other geoengineering techniques.

What are the positive and negative aspects of albedo enhancement?
When it comes to the advantages of the proposed geoengineering technique albedo enhancement, the best advantage is that it uses natural resources like sea water and wind with already existing technologies. Apart from that, it is considerably cheaper compared to to other geoengineering techniques. Cloud albedo levels could be monitored via satellite and therefore the sea spraying mechanisms could adjust to the data. Another advantage is that this geoengineering method can be controlled and localised. This helps to implement albedo enhancement only in places where it is needed. Even the debate about the optimal global temperature could be solved in this way. 

Advantages cannot exist without disadvantages right?

As with all other geoengineering techniques, there exists the fear that the actual results after the implementation happened may differ from the predicted effect and that the albedo enhancement of clouds may not be effective enough to counter climate warming.