Protecting the climate by reducing fluorinated greenhouse gas emissions

EMPA, a research institute of the ETH (Zurich): The Montreal Protocol led to a global phase-out of most substances that deplete the ozone layer, such as chlorofluorocarbons (CFCs). A happy side-effect of the gradual ban of these products is that the Earth’s climate has also benefited because CFCs are also potent greenhouse gases.

However, now a "rebound effect" threatens to accelerate the rate of global warming. Hydrofluorocarbons (HFCs), which have been used in recent years in increasing quantities as substitutes for CFCs, are also climatically very active and many are also extremely long-lived. In the renowned journal Science an international team of researchers recommends that the most potent of these gases also be regulated. This could save the positive side effect of the Montreal Protocol for the global climate.

.... Since the year 2000 the radiative forcing (a measure of the effect on the climate of chemical substances) of all ozone-depleting substances including CFCs has remained at a more or less constant value of 0.32 W/m2, compared to a value of 1.5 W/m2 for CO2. Had the Montreal Protocol recommendations not been implemented, today’s value would be approximately double this figure, i.e. 0.65 W/m2. Putting things another way, the CFC ban has prevented the equivalent of 10 billion tonnes of CO2 being emitted into the atmosphere in 2010, five times the annual reduction target set by the Kyoto Protocol.

Velders, Reimann and their co-authors fear that this positive effect will soon be negated by HFC emissions, which are currently increasing at 10 to 15% annually. n their article they state that «the HFC contribution to climate change can be viewed as an unintended negative side effect» of the Montreal Protocol. At the moment the effect is still small – about 0.012 W/m2 for all CFC substitutes combined. But it is beyond question that radiative forcing due to HFCs will rise significantly in future as a result of increasing demand and production for these substances, above all in threshold and developing countries. The atmospheric scientists estimate that this value will rise to between 0.25 und 0.4 W/m2 by the year 2050. The greatest problem is presented by saturated HFCs, which are extremely stable and survive in the atmosphere for up to 50 years, exhibiting a long-term global warming potential of up to 4000 times higher than CO2. For Empa researcher Reimann the situation is clear: "Long-lived HFCs should no longer be used in these quantities."...

Space-filling model of the 2,3,3,3-tetrafluoropropene molecule, a hydrofluorocarbon used as a refrigerant, created by Ephemeronium, public domain