Good news: The next three decades will see an end to the era of big ozone holes. NASA scientists report in a new study that the Antarctic ozone hole will be consistently smaller than 8 million square miles by the year 2040. Man-made chemicals in the atmosphere cause a hole to form in the ozone layer over Antarctica each year. Although emissions of these chemicals have been declining in recent years thanks to the 1989 Montreal Protocol, which bans the production of ozone-depleting substances, max ozone hole sizes have remained larger than 8 million square miles since the early 1990s. Using data collected by NASA’s Aura satellite, scientists were able to determine how chemical levels in the ozone hole varied each year, and predict how hole sizes would change in the future.