The Montreal Protocol and its amendments has resulted in a reduction of ozone depleting substances in the atmosphere. A key question is whether ozone has responded accordingly. Betsy has been involved in a number of papers to examine recent ozone data and determine whether the changes are attributable to changes in ozone depleting substances. Fundamentally, she determined whether the changes in ozone were appropriate in magnitude and location to present a compelling case for attribution. Her latest paper on the subject was featured on the cover of Nature.