‘To coldly go’, The Economist 24th September 2016, p.53-54
In 1974 scientists discovered that chlorofluorocarbons (CFCs), chemicals used in refrigeration and as propellants in products such as hairsprays, release chlorine into the stratosphere as they decompose. This depletes the ozone that protects Earth from ultraviolet radiation. CFCs are also powerful greenhouse gases, which absorb solar radiation reflected back from the planet’s surface and so trap heat in the atmosphere. Initially, the consequences for the ozone layer caused most concern. In 1985 a gaping hole in it was found above Antarctica. Two years later, leaders from around the world acted decisively. They signed a deal, the Montreal protocol, to phase out CFCs. Now ratified by 197 countries, it has prevented the equivalent of more than 135 billion tonnes of carbon-dioxide emissions, and averted complete collapse of the ozone layer by the middle of the century. Instead, by that point the ozone hole may even have closed up. In order to manage without CFCs, firms replaced them in applications such as refrigeration, air-conditioning and insulation with man-made hydrofluorocarbons (HFCs). These substances do not deplete ozone and last in the atmosphere for just a short time. However, they still contribute hugely to global warming. The average atmospheric lifetime for most commercially used HFCs is 15 years or less; carbon dioxide can stay in the atmosphere for more than 500 years.