The theory joins the painting of roofs white and injecting salt into clouds in the field of geoengineering, using man-made fixes to reverse the effects of climate change.
The object is to increase the albedo – the co-efficient of reflected sunlight – in order that more of the sun’s rays travel back into space, rather than being absorbed, cooling the earth.Smaller bubbles – about 10 to 100 times smaller, or 1 micron - behind a ship would lead to a brighter and longer-lasting wake, increasing albedo from around 0.02 to approximately 0.2.
If implemented aboard 32,000 large ships, could reduce the surface temperature by around 0.5°C – equivalent to a carbon offset of 85.2bn tonnes, according to Intergovernmental Panel on Climate Change (IPCC) calculations.
Most importantly, the technology already exists, and is already being used aboard ships, albeit for a different purpose – air lubrication systems such as the one on aboard bulk carrier Soyo.“I understand that for the existing air lubrication system the size of the bubbles is 1mm, a bit larger than would really be needed for geoengineering,” Julia Crook from Leeds University and author of the study, tells Seatrade Global.
“There are commercially available bubble generators that generate 1 micron bubbles and used for various applications including research.
“For the air lubrication system you want the bubbles to stay under the ship hull as much as possible but for geoengineering you want the bubbles trailing the ship or out to the sides. For air lubrication 1mm bubbles works but for geoengineering you need them to be smaller."
Now, research is being undertaken to find out whether there can be a happy medium for shipowners, reducing their operating costs as well as providing a cost-effective counter for global warming.
“If we want the shipping industry to take up a technology to help climate change they are more likely to do so if they save money on fuel so having the air lubrication system as well as the geoengineering system would help that,” Crook explains. This geoengineering requirement for micro bubbles has no commercial benefit to shipping companies unless it can come about as a good side effect of air lubrication systems.
”While there may be room for refinement of the technology once it enters mass production, it may initially require the action of IMO and other regulatory bodies to get off the ground.
“To get the fuel savings from air lubrication systems you don't require such small bubbles so there may be no commercial incentive to use the smaller bubble sizes and optimise for both fuel efficiency and increased ocean surface reflectivity. So I think there would have to be some regulatory body.”
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