The mean lifespan of methane in the atmosphere was estimated in a range between 9.6 years and twelve years. These differences are caused by the uncertainties about hydroxyl radical (-OH) concentrations and formation processes. When -OH reacts with methane, it is removed from the atmosphere, so changes in its concentration would also affect the concentration of methane. An increase in methane emissions greater than the regeneration rate of OH radicals would reduce their concentrations and so increase methane's mean atmospheric lifetime.
The reaction of methane and chlorine atoms acts as a primary sink of Cl atoms and is a primary source of hydrochloric acid (HCl) in the stratosphere.
CH + Cl → CH + HCl
The HCl produced in this reaction leads to catalytic ozone destruction in the stratosphere.