In an empty parking lot somewhere in northern California, Andrew Song and Luke Iseman inflate a balloon the size of a small car, full of sulfur dioxide. They will then launch the balloon high up into the stratosphere where it will pop, releasing its sulfur dioxide contents. 

Song and Iseman are the co-founders of Make Sunsets, a geoengineering startup that sells cooling credits. For a price, you can purchase a bit of the sulfur dioxide they’re pumping into these balloons and launching into the stratosphere, with the belief it will offset the warming effects of CO2. 

Because if you send enough sulfur dioxide into the stratosphere --- we’re talking a million tonnes a year --- it’ll significantly cool our warming planet. But the idea raises scores of complicated scientific and moral dilemmas. 

In this documentary, John Chipman goes to California to learn about the potential risks and benefits of solar geoengineering. 

Reported and produced by John Chipman, with assistance from Joan Webber and Catherine Rolfsen. Mixed by Michelle Parise . It originally aired on What on Earth. 

Storylines is part of the CBC Audio Doc Unit