Participants in the social media selfie campaign entitled This Is My #EarthStatement. Photograph: The Earth Statement

Participants in the social media selfie campaign entitled This Is My #EarthStatement. Photograph: The Earth Statement

We Homo sapiens got lucky. Very lucky. Back in the 1920s, when looking for a “safe” gas to use in refrigerators, chlorine was the element of choice in a new family of manmade chemical compounds – chlorofluorocarbons. In the 1970s, Paul Crutzen, Mario Molina and Sherwood Rowland discovered that while it was safe in our fridges, it was destroying the ozone layer, which is essential to protect all life on land.

Luck struck twice. Nasa scientists measuring ozone above Antarctica in the 1980s never saw the ozone hole in their data. Their computers were programmed to ignore any figures deemed “impossible”. Luckily, the British Antarctic Survey had no such technology and sounded the alarm. In 1987, nations signed the Montreal Protocol outlawing CFCs.

But here luck comes in threes. Bromine is as good as chlorine for fridges and air conditioners, but about 40 times more corrosive to ozone. And by mere chance, the industry chose chlorine as the global standard. If this had not happened, the ozone layer could have been ripped apart before we even knew it. In 1995, Crutzen, Molina and Rowland were awarded the Nobel prize in chemistry, obviously.

Remarkably, 2015 is the make-or-break year and all the signs are there that we are changing course – a great transformation is not only within sight, it is under way. Here’s why. First, world leaders met in New York recently to agree the sustainable development goals – applying equally to all nations. This is a paradigm shift in thinking; it acknowledges for the first time that our wellbeing, the global economy and human development all rely on a stable biosphere and that this very stability is at risk. Second, we have reached “peak child”; the number of children in the world is no longer increasing. Population will eventually stabilise at 10-12 billion. And third, world leaders meet again next month to seek a workable solution to the climate challenge.

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