The shipping industry gets blamed for its share of environmental ills, from air and water pollution to collisions that kill whales and other marine animals.
But in a new paper published last week in the Journal of Geophysical Research: Atmospheres, scientists argue that the wakes of big ocean-going vessels might actually be used to curb global warming.
The scientists say that dramatically extending the lifetimes of the foamy wakes (and making them a bit brighter) would boost the Earth's surface reflectivity (what scientists call albedo) and reduce the extent to which sunlight warms our planet.
Wake bubbles typically pop within a matter of minutes. But "if we could make the bubbles in the wake last for 10 days, then I believe this scheme could potentially reduce global warming to some extent," Dr. Julia A. Crook, a research fellow in the Institute for Climate & Atmospheric Science at the University of Leeds in England, told The Huffington Post in an email.
Crook and her co-authors maintain that their climate model shows the scheme could bring a 0.5-degree Celsius reduction in the Earth's average surface temperature by 2069, helping to offset the 2-degree warming expected by then.
According to Crook, the effect is comparable to those achieved by other so-called geoengineering schemes that have been proposed in recent years.
Of course, those bubbles won't resist popping just because we want them to. The scheme calls for the ocean-going ships to pump out a stream of chemicals known as surfactants as they move along. Surfactants help prevent popping by affecting the surface tension of water -- at the same time making the wakes a bit whiter than they would be ordinarily.
But it's not clear whether the scheme would be safe for marine life. And then there's the matter of its effect on air quality.
"Previous research suggests surfactants reduce the amount of CO2 uptake by the ocean, which would mean by adding surfactant we might cause atmospheric CO2 to go up," Crook said. "But by how much and whether the resulting warming from the extra CO2 would outweigh the increased albedo is unknown. This could be a show-stopper."
Dr. David Keith, a professor of applied physics and public policy at Harvard and a noted expert on geoengineering, said real-world feasibility and cost are other key issues.
"Nobody doubts that if you can make the bubbles last it makes the sea whiter," Keith said. "That’s easy. The hard part is whether you can make the bubbles persist and do it in sea water."
To fully assess the scheme's cost, safety and feasibility, he said, it will take more than a climate model. It will take real-world experiments.
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