 The arctic polar cap stratosphere has been affected by rising greenhouse gas concentrations and decreasing anthropogenic ozone-depleting substance concentrations. These changes have caused the stratosphere to warm more than expected, leading to increased variability in the atmosphere. This variability is most pronounced in the lower stratosphere, where the effects of ozone warming and carbon dioxide cooling are offsetting each other. Under extreme future conditions, such as four times the amount of carbon dioxide in the atmosphere, the effects of ozone warming and carbon dioxide cooling are not as pronounced, but still exist. This article was authored by Jessica Colt Herdin, Timothy Sukadoloff, Gabriel Ciodo, and others.