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The Paris climate agreement defines a clear aim to limit global warming to less than 2^OC, and perhaps even to less than 1.5^OC.  The commitment of governments around the world to those targets is a huge achievement, but the Paris Agreement did not establish the specific routes by which that protection would actually be delivered.  With the “Kigali amendment” of the Montreal Protocol one of those routes is now clear. 

The “Kigali amendment” controls the production of one group of extremely powerful greenhouse gases under the same global treaty that protects the ozone layer.  At first sight it may seem surprising that it is the Montreal Protocol that is making this major contribution to preventing climate change. In fact, the Montreal Protocol has not only delivered all the benefits of successfully protecting the ozone layer, it also has an excellent track-record of protecting the climate. The Kigali amendment now builds substantially on that success.

Controlling ozone depleting substances has also reduced global warming

The Montreal Protocol has protected the climate because many of the chemicals that damaged the ozone layer, ozone depleting substances or “ODS”, were also very potent greenhouse gases. For example, one chlorofluorocarbon, CFC12, is almost 11,000 times more powerful than CO₂ as a greenhouse gas. 

We have emitted much lower quantities of ODS than CO₂.  Even so, it is estimated that that the warming effect of ODS emissions was equivalent to around 40% of the warming effect attributable to CO2 emissions. Without the Montreal Protocol that figure would have remained at around 40%. The successful implementation of the Protocol has reduced the contribution of ODS to around 20%.

To put that in context, this reduction in ODS already delivered through the Montreal Protocol is estimated to be about five times the climate benefit than the target set by the Kyoto Protocol for 2008–2012.

Halving the contributions of ODS to global warming has been achieved because the first generation of CFC-replacements, HCFCs (hydrochlorofluorocarbons), were not only much safer for the ozone layer, they were also much less potent greenhouse gases than most CFCs.  However, over time HCFCs have been replaced by HFCs (hydrofluorocarbons). 

HFCs - safe for the ozone layer but a major threat to climate

HFCs are effectively completely safe for the ozone layer and some are also only weak greenhouse gases. However, other HFCs are much less benign to the climate. Some are even more powerful greenhouse gases than the CFCs that they ultimately replace. One, HFC23, is almost 15,000 times more potent as a greenhouse gas than CO₂. 

The major uses of this new generation of potent greenhouse gases include refrigeration and air conditioning.  The need for effective food storage and our changing expectations for “comfort cooling” mean that demands for both these technologies are set to increase massively over the coming decades. If that demand had been met using those HFCs that are potent greenhouse gases, then HFCs would have made a significant contribution, around 0.5^OC, to warming over the rest of this century.

Years of negotiations have finally paid off

Avoiding that 0.5^OC warming by controlling HFCs has been the subject of detailed discussions at Meetings of the Parties of the Montreal Protocol since 2009.  In 2015 the 27^th Meeting of the Parties agreed the “Dubai pathway on HFCs”. The last year has seen ever more intense negotiations leading up to the 28^th Meeting of the Parties. So the Kigali amendment is the result of years of long, hard negotiation.  That a powerful amendment was agreed is a tribute to systems that have successfully protected the ozone layer for three decades. 

Once again while it is the climate talks, like Paris last year, that grab most of the media attention, it is the Montreal Protocol that has really delivered the actions that we all depend on to protect our global environment.

Read Nigel’s article in The Ecologist about why the Montreal Protocol has been so effective.