The Theory
The theory behind cloud whitening is deceptively simple: modify the composition of clouds by injecting them with seawater in order to make them whiter. Injection of salt water theoretically increases the clouds’ “condensation nuclei,” making them smaller and more reflective. Up to 25% of the world’s oceans are covered with thin low-lying stratocumulus clouds (below 2400 meters). Cloud whitening is another solar radiation management technique and, like simulating volcanic eruptions; the technique may reduce the temperature of the atmosphere and the oceans, but would not reduce levels of greenhouse gases. It is imagined that fleets of unmanned vessels would spray mist created from drawn seawater into the clouds above.
Who’s involved?
The most prominent scientists advocating for cloud whitening are John Latham from the National Center for Atmospheric Research at the University of Colorado (USA) and Stephen Salter from the University of Edinburgh (UK). Based on “very artificial” modeling techniques that assume “perfect cloud condensation nuclei,” Phil Rasch of the Pacific Northwest National Laboratory argues that seeding the clouds above a quarter to a half of the world’s oceans (!) could offset warming by 3 watts per square metre, or, as Latham and Salter hypothesize, “subject to resolution of specific problems,” cloud whitening “could hold the Earth’s temperature constant as the atmospheric CO2 concentration continues to rise to at least twice the current value.” Others have contested these optimistic calculations, however.
What’s wrong with cloud whitening?
As recently noted by the American Meteorological Society in its draft statement on geo-engineering, proposals that reduce the sunlight reaching the earth would not only cool the temperature, but “could also change global circulation with potentially serious consequences such as changing storm tracks and precipitation patterns throughout the world.” Altering the composition of the clouds over a quarter to a half of the earth’s surface will affect weather patterns and could disrupt marine ecosystems, including bird and plant life. The technique is also inherently transboundary and should require international agreement. For example, models show that one of the most effective areas to target would be off the coast of California and Peru but this may adversely effect coastal rainfall and hence agriculture. Although there have been well-founded rumours regarding plans to experiment with this technology in the Faroes Islands, located between the Norwegian Sea and the North Atlantic, these have not been confirmed and public queries from ETC Group have not provided clarification.
