Temperature rises in the stratosphere due to the absorption of solar ultraviolet radiation by ozone. The ozone layer performs the vital role of protecting all terrestrial life from the damaging effects of UV radiation. In fact, terrestrial life could not appear until there was sufficient ozone to provide this protective shield. We will start by looking at the photochemical reactions which form the ozone layer, plus some catalytic reactions which reduce the amount of ozone. We will then briefly look at the major biological impacts of the UV radiation which the ozone layer largely, though not completely, filters out. The Ozone Hole will be discussed in the last two sections. The first will examine just what is the cause of the hole, and why it is largely confined to Antarctica. Finally, we look at the Montreal Protocol that has saved it, and us (fingers crossed).

Magnificent piece of statecraft though it is, the Paris Agreement is unlikely to spare us from a future climate reckoning. Paris can be seen as the successor to a series of prior global emissions limitation agreements including the breathtakingly effective Montreal Protocol that addressed the cause of the “ozone hole” and the Kyoto Protocol, the world’s first attempt to address climate change. Kyoto collapsed in failure and Paris was therefore midwifed with the Kyoto lessons in mind. We then delve into the structure, status, and limitations of the Paris Agreement before looking ahead to how it might evolve.

The discovery of the Antarctic ozone hole in 1985 is chronicled, making the analogy with the concept of the “black swan,” a metaphor for unprecedented events. The ozone layer in the stratosphere acts as a shield for life on the Earth, by blocking harmful ultraviolet radiation from the sun. Concern mounted in the 1970s that compounds known as chlorofluorocarbons, used as refrigerants and coolants, could be slowly destroying the ozone layer. Joe Farman and the British Antarctic Survey (BAS) found that ozone levels in the stratosphere had dropped dramatically during the Antarctic spring season in the 1980s, creating a “hole” in the ozone layer. US scientist Susan Solomon led an expedition to make measurements of the ozone hole and worked with colleagues to explain the cause: cold Antarctic temperatures allowed the formation of polar stratospheric clouds that catalyzed chemical reactions involving CFCs, leading to rapid ozone loss.