Feature Story

Protecting the climate and the ozone layer together

September 14, 2017

The ozone layer is healing, and is likely to recover in several decades. Photo: Shutterstock

By Mario Molina, winner of the Nobel Prize for chemistry for his work on ozone depleting substances

On 16 September 2017, the world celebrates the 30th anniversary of its most effective global environmental agreement ever created. Indeed, the Montreal Protocol on Substances that Deplete the Ozone Layer has a claim to be one of the most successful treaties of any kind. The first and only treaty ever to be ratified by all the world’s nations, it has succeeded in putting the stratospheric ozone layer on the road to recovery, and done more than any other measure, so far, to slow down climate change.

The danger that chlorofluorocarbons (CFCs) posed to stratospheric ozone was the first recognised human threat to the global atmosphere. The ozone layer shields terrestrial life from deadly ultraviolet radiation, and if it had continued to be depleted, the worldwide consequences would have been catastrophic, with many millions of people developing skin cancer and widespread damage to crops.

In 1974 F Sherwood Rowland and I published a scientific paper that concluded that CFCs were migrating to the upper atmosphere and affecting the ozone layer. This was initially disputed by many, but confirmed practically beyond doubt by later scientific and empirical evidence. While the chemical industry initially questioned the science, they subsequently agreed to develop replacement chemicals that would not affect the ozone layer.

Then, a decade after our original paper, research revealed a “hole” in the ozone layer above Antarctica. The magnitude of the ozone loss was so unexpected that the scientists who made the discovery originally thought that their instruments were faulty. But again, empirical and scientific evidence both confirmed its existence, and that it was caused by CFCs and related chemicals.

This catalysed the successful development of the Montreal Protocol, concluded in September 1987. Initially the countries that were party to the treaty agreed just to reduce CFCs by 50% over 12 years. But, at their first annual meeting after it came into force, they increased the reduction to 75% by 1998 and in 1992 they tightened it again to a 100% phase-out by 1996.

The treaty aimed at starting, then strengthening, action. And success has continued to breed still more success. Over three decades it has reduced nearly 100 ozone-depleting chemicals by nearly 100%. The ozone layer is healing, and is likely to recover in several decades.

That, however, is only the start. The same chemicals that attacked the ozone layer also warmed the climate. Thus, in phasing them out, the Montreal Protocol has made a large contribution to protecting the world’s climate.

The Montreal Protocol is, therefore, indeed a unique, planet-saving agreement. And it is still getting stronger, and playing a critical role safeguarding the global commons of the planetary system.

Last October in Kigali, Rwanda, the world’s governments agreed to a far-reaching amendment to the protocol which will phase down the use of hydrofluorocarbons (HFCs), one of the six main pollutants causing global warming. HFCs were introduced as ozone-friendly alternatives to CFCs and other damaging chemicals, and so helped protect the ozone layer. But they threatened the climate, because molecule-per-molecule they are up to 4,000 times as powerful in warming the atmosphere than carbon dioxide – and their use has been rapidly growing, by some 10-15% a year.

The adoption of the amendment – after an eight-year campaign, initiated by the Federated States of Micronesia and other low-lying countries – will prevent the emission of the equivalent of 100bn tons of carbon dioxide by 2050; and avoid up to a half degree Celsius of warming by the end of the century. Put another way, had it not been passed – and HFC use continued as expected – the amount of fossil fuels that could still be burned without dangerously affecting the climate would have shrunk by 30-60%.

Moreover, this already enormous benefit for the climate could possibly be doubled. Emissions could be cut twice as much – to the equivalent of 200bn tons of carbon dioxide, 34 years of current US emissions, by mid-century – if the efficiency of air conditioners and other cooling appliances is improved as HFCs are withdrawn.

When other refrigerants have been replaced in the past, manufacturers have seized the chance to upgrade components, thus improving energy efficiency. Besides dramatically reducing emissions, taking similar measures now would save consumers money and expand access to affordable cooling, since energy use accounts for 80% or more of the lifetime cost of an air conditioning unit.

These measures can, and must, complement the international action enshrined in the Paris agreement on climate. Governments should quickly ratify the Kigali amendment, and where possible, consider accelerating the phase-down schedule for HFCs. Cutting emissions of these damaging chemicals has a much faster effect than action against carbon dioxide because they stay in the atmosphere for only a decade and a half on average, compared to carbon dioxide, where a significant fraction stays for hundreds and even thousands of years. Governments must also seize the opportunity to improve the efficiency of air conditioners and other cooling products and equipment, in parallel with the phase down of the HFC refrigerants.

Avoiding dangerous climate change may often seem hard. But the 30-year-old Montreal Protocol has not just made it easier by eliminating several dangerous greenhouse gases, but it has shown how the world can unite to avert a global threat to the atmosphere, and offers lessons for how the agreement made in Paris can now be strengthened. Perhaps most important of all, it provides hope and inspiration for the daunting task ahead.