Global warming is so rampant that some scientists say we should begin altering the stratosphere to block incoming sunlight, even if it jeopardizes rain and crops
O n the crisp afternoon of February 12, 2023, two men parked a Winnebago by a field outside Reno, Nev. They lit a portable grill and barbecued a fist-sized mound of yellow powdered sulfur, creating a steady stream of colorless sulfur dioxide (SO2) gas. Rotten-egg fumes permeated the air as they used a shop vac to pump the gas into a balloon about the diameter of a beach umbrella. Then they added enough helium to the balloon to take it aloft, attached a camera and GPS sensor, and released it into the sky. They tracked the balloon for the next several hours as it rose into the stratosphere and drifted far to the southwest, crossing over the Sierra Nevada Mountains before popping and releasing its gaseous contents. The contraption plummeted into a cow pasture near Stockton, Calif.
The balloon released only a few grams of SO2, but the act was a brazen demonstration of something long considered taboo—injecting gases into the stratosphere to try to slow global warming. Once released, SO2 reacts with water vapor to form droplets that become suspended in the air—a type of aerosol—and act as tiny mirrors, reflecting incoming sunlight back to space. Luke Iseman and Andrew Song, founders of solar geoengineering company Make Sunsets, had sold “cooling credits” to companies and individuals; a $10 purchase would fund the release of a gram of SO2, which they said would offset the warming effects of a metric ton of atmospheric carbon dioxide for a year. They had planned a launch in Mexico but switched to the U.S. after the Mexican government forbade them.