John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
If it comes down to it, water-shooting ships just might help geoengineer us away from a hotter future, according to some new research.
Battling a big problem like climate change will require big ideas. And scientists in the U.K. have one of the biggest: take ocean water, shoot it up into the atmosphere, and let the resulting clouds cool the earth like a massive, wet blanket.
Granted, these folks are not the first to float this incredible-sounding strategy, known as "marine-cloud brightening." In one example, the physicist John Latham wrote in 1990 that the life of clouds might be prolonged by artificially increasing their "droplet concentration." These thicker clouds would reflect more of the sun's radiation away from the planet, in theory allowing its fever to diminish.
But researchers at the University of Manchester and elsewhere have drafted a road map for what they think is the world's best marine cloud-seeding plan. They envision a fleet of ships traveling the oceans, spraying vast quantities of seawater into the ether with a technique called the "Rayleigh jet." (In this study, the Rayleigh's efficiency beat other methods such as the "Taylor cone jet" and "effervescent spray atomization.") Dispersed in the higher altitudes, the water would leave behind fine salt crystals that serve as nuclei for cloud formation.
Here's the takeaway of their paper, recently published in the journal Philosophical Transactions of the Royal Society A:
The researchers tested each technique so there was an increase in reflection of 5%, a figure that would combat the predicted effects of increased carbon dioxide levels over the rest of this century. They then looked at how much energy each would consume.
The scientists say that the Rayleigh jet method could produce the desired effect using 30 megawatts of energy, about the same energy that two large ships produce.
So is this the answer to our overheated world's problems? Maybe not, as the desirability of geoengineering tactics is much in debate. Perhaps the most basic issue is we probably won't be able to tell if they're working. "[H]ow much sunlight Earth reflects naturally varies a lot—not just from place to place and season to season, but even for the same month from year to year," writes NOAA. "The bigger the range of natural variability, the greater the odds that any evidence of a manmade effort to brighten up the planet would be lost in the 'background noise.'"
There's also the concern that denser clouds could interfere with solar-energy infrastructure, a key component in moving away from carbon fuels. Seeding the atmosphere with aerosols could lead to a drop in energy production at solar facilities of as much as 20 percent, according to one NOAA study. And in a 2011 paper in Climatic Change, scientists threw out two more objections: that putting resources into geoengineering rather than cutting emissions "constitutes a conscious risk transfer to future generations, in violation of principles of intergenerational justice," and it could be disastrous if things were to go wrong:
A failure to maintain the aerosol counterforcing (for example in the case of a war, a breakdown of an international agreement, or the discovery of sizable negative effects due to the aerosol forcing) would lead to an abrupt warming with rates that are unprecedented for modern human societies and would likely cause sizeable economic damages.
Perhaps that's why the U.K.'s Paul Connolly, an atmospheric scientist involved in this latest research, sounds cautious about this oceanic-pumping scheme. "I am not recommending that we use any of these techniques now, but it is important to know how best to use them should they become necessary," he says. "Should no progress be made to reduce CO2 levels, then geoengineering techniques, similar to this, might become necessary to avoid dangerous rises in global temperatures."