The lightning bolts that streak across the sky during thunderstorms emit a gas found in car exhaust—nitrogen oxide (NO). This gas can adversely affect air quality and trigger respiratory illnesses in humans, but how lightning-generated nitrogen oxide affects the atmosphere is less clear. This molecular disruption creates nitrogen oxide, nitrogen dioxide (NO₂), and other types of nitrogen oxide gas. While there is significantly more human-generated pollution in the atmosphere, lightning releases nitrogen oxides at much higher altitudes. “We believe that when storms get more intense, lightning flashes get shorter and produce less nitrogen oxide per flash,” said Allen.