NewsAugust 29, 2012

Scientists Suggest 'Cloud Brightening' To Halt Hurricanes

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Michael D. Lemonick

By Michael D. Lemonick

As Tropical Storm Isaac batters southeastern Louisiana and nearby coastal areas with surging seas, howling winds, and torrential rainfall, it’s nearly impossible to imagine that humans could have done anything to stop such powerful force of nature.

Nearly impossible, but not quite.

A team of atmospheric scientists, writing in the journal Atmospheric Science Letters, has imagined precisely that. They suggest that brightening the clouds that float above hurricane-forming regions could effectively cool the sea surface below, thus depriving tropical storms of the heat on which they depend to sustain their destructive power.

Credit: egoyodax/flickr

“We’re probably a couple of years away from being able to conduct field tests,” said lead author John Latham, of the University of Manchester, England. “But as these things go, it probably wouldn’t be very expensive.”

The hurricane-stopping technique is a smaller-scale version of an idea Latham and others have proposed to slow global warming all over the planet. Known as marine cloud brightening, or MCB, it’s one of many versions of geoengineering — the idea of counteracting global warming with some sort of technological counter-measure to cool the planet, prevent heat-trapping CO2 from entering the atmosphere, or sucking it out once it’s there

With MCB, scientists propose to spray microscopic droplets of sea water into clouds that typically cover a quarter or so of the ocean’s surface at any given time, perhaps using unmanned Flettner rotor ships guided by satellites. In theory, at least, the effect would be to make the clouds more reflective, so that more of the sunlight that hit them would bounce back into space without warming the Earth.

Latham and his colleagues published a major study on MCB in the journal Philosophical Transactions of the Royal Society last month; the new study on hurricane suppression, Latham said, “is kind of a reduced-area version,” targeted at patches of ocean off the coasts of Africa, South America and North America where hurricanes and Pacific typhoons are often born. “As soon as oceanic waters start to receive less sunlight,” Latham said, “the cooling will start.”

It will, that is, if the technology behind cloud brightening moves forward. “There will be opposition to any kind of geoengineering,” Latham said, largely because of the fear that something could go very wrong.

“We don’t claim to have dotted every ‘i’ and crossed every ‘t’ on this issue,” Latham said. “We need to look very closely at the issue of adverse consequences.”

That’s the case, not just with this project, but with every form of geoengineering, where the specter of unintended consequences haunts even the best-intentioned of projects. One possible side effect of reducing the sunlight reaching Earth, for example, could be reduced rainfall in Europe and North America.

The danger is less for hurricane suppression simply because it could conceivable be done in over a very small area — as little as 5 percent of the ocean surface, according to the new study.

“The way it stands at the moment,” Latham said, “is that if we can get this to work, it should be possible to choose where to seed, both on basis of cooling the surface water, but also on not cooling over land in regions that won’t tolerate it.”

Nevertheless, says the paper, the climate models that develop these reassuring conclusions aren’t reliable enough yet to be trusted. “We conclude therefore,” write the authors, “that it is possible that unacceptable rainfall changes may result from MCB seeding, and if these cannot be corrected MCB should never be deployed.”

The conclusion, Latham said, is that, “we’re not ready to do even small-scale experiments yet. We need to carry this work a bit further theoretically.”