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Brighter World Dummies' Guide

An Introduction to Whitening Clouds

Stehpen Salter and John Latham want to fight climate change by changing the albedo (the extent to which an object reflects light from the sun) of marine stratocumulus clouds. Why marine stratocumulus clouds? They're common across the world and, because they're low-lying, the clouds are easily reached from sea level.

Generally, stratocumulus clouds do not cause rainfall, so the salt particles Salter and Latham would use to change the clouds' reflectivity would not be washed out.

Main Experiment

The team will test the principle of whitening clouds using flares loaded with a hygroscopic (readily taking up and retaining moisture) material.

Approximately 300 flares will be released at sea level from a boat moored off the South African coast. The flares produce a plume of micron-diameter potassium chloride and sodium chloride particles – both of which occur naturally in seawater, and are used for cloud seeding around the world.

Salter and Latham will use aircraft to track the progress of the plume through the marine boundary layer as well as any impact the plume might have on the diameter of cloud droplets. The team is looking for a shift from 25 microns to 16 microns within a stratocumulus cloud.

Flare release will last for around three minutes, firing all flares at the same time. Monitoring flights will last for two hours post flare release.

Supplemental Experiments

Test 1: The team will measure the size of water particles in clouds by flying through low-level stratocumulus clouds using specially instrumented aircraft to detect and measure cloud droplet diameter.

Test 2: The team will collide two high-pressure water jets to try to create micron-diameter droplets of saline water. They'll monitor the test using a special laser-based droplet measuring system.

Test 3: The team will test the concept of the Flettner rotor, a 1920s invention that is purported to be a more efficient way of powering a boat than sails or engines. The team converted a 34-foot trimaran originally used for ocean cruising into a vessel powered by two 30-foot-tall Flettner rotors (rotating cylinders approximately 2 feet in diameter). They will then test the boat off the coast of Florida, comparing its speed, maneuverability and efficiency against a traditional sailboat and motorboat.

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