Solar geoengineering schemes that involve spraying sun-reflecting particles near the poles to counteract global warming could expose passengers on certain commercial flights to hazardous levels of sulphuric acid. Researchers have begun to investigate how planes could be upgraded to deposit sun-reflecting compounds in the sky near the poles, which poses a potential hazard to flights that follow polar routes. Atmospheric models suggest that injecting 12 million tonnes of sulphur dioxide into the stratosphere could odlično the globe between 0.6 and 1.0°C.