10494640_lThe phase-out of ozone-depleting CFCs may be behind the apparent “pause” in global temperature rises, according to a new study.

While these gases were banned under the Montreal Protocol due to their detrimental effects on the ozone layer, the report suggests that their removal may also have had a marked effect on climate change.

The new study published in Nature Geoscience magazine acknowledges the increase in global temperatures by 0.8 °C over the past century but says the  link to human activities remains less clear, particularly because of the apparent slow-down in warming since the late 1990s.

The report maintains that the CFC phase-outs that cam as a result of the establishment of Montreal Protocol in 1989 also had an impact on global warming.

The authors, from Mexico, the Netherlands and USA, conclude that the reduction in the emissions of ozone-depleting substances under the Montreal Protocol, as well as a reduction in methane emissions, contributed to the lower rate of warming since the 1990s.

High GWP

What is often forgotten is that some of these formerly commonly used CFCs also had high global warming potentials. Amongst the commonly used refrigerants at the time, R12 had a GWP of 2,400, while R11 possessed a GWP of 4,000 – far higher than current HFC R404A’s GWP of 3,300.

And these were used at a time without any leakage prevention controls on systems and when venting refrigerant to atmosphere was an accepted procedure. These CFCs were also used as propellants in aerosols and foam production.

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