Ozone Layer Recovering

One of the most-anticipated questions in environmental science may have been answered last week. Earth’s long-beleaguered ozone layer, which has been much reduced by industrial chemicals such as chlorofluorocarbons (CFCs), is starting to show evidence of recovery. Scientists have long suspected that the ozone layer would recover on its own after governments signed the Montreal Protocol in 1987 and its follow-up amendments, but they did not know when this would happen. Scientists in the United States and the United Kingdom, who have examined the data set of ozone-layer information since 2000, believe they have seen the first real proof of the ozone layer’s healing.

The ozone layer is the region of the upper atmosphere, between roughly 15 and 35 km (9 and 22 miles) above Earth’s surface, containing relatively high concentrations of ozone molecules (O3). During the 1970s and ’80s, scientific studies revealed that CFCs, halons, and other chlorine-containing chemicals released by industry were reacting chemically with ozone, stripping away single oxygen atoms and reducing the thickness of the layer. The ozone layer blocks much of the incoming ultraviolet radiation from the Sun, and its thinning (which has resulted in the development of “ozone holes” over the Arctic Ocean and Antarctica during each region’s coldest months) has been linked to increasing rates of skin cancer, eye cataracts, and genetic and immune-system damage. The Montreal Protocol, initially signed by 46 countries and later adopted by nearly 200 signatories, was the treaty that guided the rapid systematic phaseout of ozone-depleting chemicals (ODCs).

With ODC production halted, the world waited for signs of recovery. It wasn’t until 2014 that scientists observed the first small increases in stratospheric ozone in more than 20 years; however, a study published in June 2016 was confident enough to announce proof of the good news. The study, which tracked the evolution of the size of the ozone hole over Antarctica, observed that the Antarctic ozone hole had declined by half the size of the continental U.S. between 2000 and 2015. On a planet plagued by a host of environmental problems, this announcement offered hope—hope that the ozone layer would one day return to normal (perhaps sometime between 2040 and 2070) and hope that governments could set aside their differences to solve a serious environmental problem.