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).

Chapter 1 offers a historical examination of the causes and discovery of global heating and the development of the scientific consensus that it is human-caused and can be curtailed only by cutting greenhouse gas emissions and describes how those developments nonetheless failed to lead to extensive action.

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.

Because of its transboundary effects and because states will be the primary actors, large-scale solar geoengineering and its governance are matters of international law. This is the second of four chapters that consider international legal rules, here regarding the climate and the atmosphere. Climate change is, and solar geoengineering would be, foremost atmospheric phenomena. The UN Framework Convention on Climate Change and its protocols – the central legal regime for international cooperation to limit climate change and its impacts – offer surprisingly limited guidance for solar geoengineering. However, the regime could provide an institutional site for future multilateral governance. Some provisions of the Vienna Convention for the Protection of the Ozone Layer and the Convention on Long-Range Transboundary Air Pollution (and their protocols), which regulate substances that contribute to stratospheric ozone depletion and to acid rain, respectively, would be applicable, depending on circumstances. The International Law Commission has approved Draft Guidelines on the Protection of the Atmosphere, one of which addresses activities aimed at its intentional large-scale modification.