In 1990, British cloud physicist John Latham published a paper arguing he could cool global climate by brightening clouds over the ocean. Most colleagues ignored the paper, titled “Control global warming?”—probably because this thing called global warming was not yet a hot topic.





Now, more than two decades later, Latham continues to develop what has become one of the most promising and controversial ideas in climate control. “Marine cloud brightening” might sound benign, but hairs rise when it’s called “geoengineering.”





“It’s a horrible word. It scares people,” said Latham, who now currently works at the University Corporation for Atmospheric Research in Boulder, Colorado, in an interview with mongabay.com. “It’s a kind of Dr. Strangelove term. What we’re trying to engage in is climate restoration.”





Latham targets thin, low-lying marine stratocumulus clouds that naturally shield about one-fifth of Earth’s surface. They reflect five times more sunlight than does the ocean surface, so they cool the planet by deflecting radiation that the ocean otherwise would absorb.









An unmanned, wind-powered rotor ship currently under development as a potential transport device for sprayers to propel saltwater particles into the atmosphere. Artist’s impression by John MacNeill.

Latham argues that forcefully injecting tiny saltwater particles into the air above the sea surface could attract water droplets to form even more reflective versions of these clouds. On a large-enough scale, these clouds could stabilize global temperatures as carbon dioxide levels continue to rise into the next century.





Creating such minuscule particles on a massive scale remains challenging. Engineer Armand Neukermans, who helped invent inkjet printing for Hewlett Packard, has teamed up with Latham to develop inkjet-like tools—high pressure pumps attached to very tiny nozzles—to spurt salt particles less than one-billionth the size of ink droplets in printers. A prototype should be ready to test within six months, Latham said.





However, to show whether this could work at sea over many years, the team needs more funds. Potential funders remain apprehensive about the project’s unknown environmental implications, especially its possible impacts on global rainfall patterns. But in a recent summary of their work in the Philosophical Transactions of the Royal Society A, Latham and 24 colleagues emphasize that they do not intend to deploy cloud machines on a large scale until research proves them safe and viable.





“I think most scientists think this basic idea will work in some places,” Ken Caldeira, a Stanford University climate scientist, told mongabay.com. “The discussion is really what’s the strength of this effect and in how wide of an area would it work.”





Latham estimates the project would require a fleet of 1,500 autonomous ships, steered by satellite, each spraying hundreds of thousands of salt particles into the air every second, to affect global climate. The price of the fleet could reach US $1.5 billion in the first year. But Latham considers that trivial compared to the long-term cost of climatic catastrophes; Superstorm Sandy alone caused an estimated US $40 billion in damage in October.





Cloud brightening is reversible, Latham notes. If something went wrong, the team could turn off the machines. All artificially brightened clouds would disappear within days.





But what would happen to Earth’s climate if thousands of reflective shields suddenly disappeared? Such unknowns are among the many stigmas of geoengineering that Latham hopes to clear up.





“We’re dedicated to it,” he said, of tackling climate change. “If one steps back, it’s a pretty gloomy picture at the moment, but it doesn’t seem insoluble.”

CITATION: John Latham et al. Marine cloud brightening. Philosophical Translations of the Royal Society A, 13 September 2012. DOI:10.1098/rsta.2012.0086





Laura Poppick is a graduate student in the Science Communication Program at the University of California, Santa Cruz.

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