Science

Background - 11 September, 2009
Climate scientists can measure how effective a greenhouse gas is at warming the planet over a certain period of time. The measurement (global warming potential, or GWP) compares the potency of a greenhouse gas to carbon dioxide (CO2), which has a GWP of 1. So for example, a F-gas with a 100 year GWP of 1000 is 1000 times "better" at warming the planet over 100 years than CO2.

Measuring Global Warming Potential

The measurement of global warming potential changes depending on what timescale you use, for example, 20 years compared to 100 or 500 years. By convention, scientists look at a 100-year time scale when converting the global warming potential of a HFC gas to the equivalent in CO2. There are a number of HFCs, with 100-year global warming potentials ranging from 53 to 15,000. However, a lot of HFCs have a much shorter lifetime than 100 years, so their full impact on the climate is not accurately represented by such a measure. This is shown below with the most common HFC in use today: HFC 134a.

If you bought your home refrigerator or your car in the USA in the last ten years, it almost certainly uses HFC 134a for chilling. This chemical has a GWP of 1430 over 100 years. It shoots up to 3830 when measured over twenty years - roughly the time this gas hangs around in the atmosphere. So the 300 grams in your refrigerator is equivalent to 1150 kg of carbon dioxide, over a 20-year time frame. That's the same amount a car emits over 7000 kilometres, more than driving from Paris to New Delhi.

However, if you bought your refrigerator in Europe in the last ten years, it almost certainly uses a hydrocarbon refrigerant (no fluorine in there!) that was designed, prototyped and open-sourced by Greenpeace in 1992.

Contribution of F-gases to global warming

To work out how much this group of gases contributes to global warming uses another measurement, called radiative forcing ( see the "Measurements of global warming impact" fact sheet). This describes how much  a particular greenhouse gas heats up every square meter of the planet.

CFCs and HCFCs, which deplete ozone, and the HFCs that replaced them, were directly responsible for 17 percent of man-made global warming in 2005 (and 20 percent this year). The amount of HFC 134a in the atmosphere is growing by 20 percent a year. A recent report by top scientists shows that if we only focus on reducing CO2 and do nothing about HFCs, they will be responsible for 28-45 percent of climate change by 2050. Even if we didn't act on CO2 they would still be responsible for 10-20 percent of climate change by 2050. The threat of F-gases is real, and the time to act is now.

These super-greenhouse gases could undo all of the good work of the Montreal Protocol that phased out ozone-depleting gases, turning it into a huge climate change culprit.

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