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. But, like CFCs, HFCs cause a greenhouse effect between hundreds and thousands of times as powerful as carbon dioxide while they linger. Total emissions are still relatively low, but are rising by 7-15% a year. Controlling HFC emissions has been under discussion for the past decade; America and China, the world’s two biggest polluters, made a deal on the issue in 2013, which paved the way for co-operation on limiting carbon emissions ahead of UN-sponsored climate talks in Paris last year. There leaders agreed to keep warming “well below” levels expected to be catastrophic.
Average global temperatures are already 1°C higher than in pre-industrial times….America wants action on HFCs speedy enough that emissions will peak in 2021 and then start to fall; after recent talks in Hangzhou between Mr Obama and Mr Xi China may be ready to commit to reaching that point by 2023. Brazil, Indonesia and Malaysia lean towards 2025, and India has lobbied for a later date, closer to 2030.
Some sectors firms are already preparing to move away from HFCs: in 2015 the Consumer Goods Forum, an international industry group whose members include Walmart and Tesco, began enacting a plan to phase out the substances.
A big question is what to use instead….Some HFCs commonly used in refrigeration could be replaced by others that would have an impact more than 1,000 times smaller. Honeywell, an electronics giant, already makes these less-damaging alternatives. But patents covering such substances have been a sticking point in past discussions, says Achim Steiner, until recently the head of the UN Environment Programme….Other possible replacements include isobutane, propane and propylene, all of which occur naturally. These hydrocarbons are cheap and non-toxic, and can be used as coolants without the same harm to the ozone layer….
Excerpts from The Montreal protocol: To coldly go, Economist, Sept. 24, 2016,at 58