To demonstrate how they would disperse the sulfur dioxide, they had planned to float a balloon over Norfolk, at an altitude of a kilometre, and send a hundred and fifty litres of water into the air through a hose.

NEWYORKER: The Climate Fixers

The hose is connected to a machine that lowers the air's oxygen content, thereby simulating a mountaintop environment.

NPR: Anti-Doping Agency Reviews Low-Oxygen Tents