F-gas plot

This shows the emissions, concentrations or radiative forcing from the CFCs, HCFCs, HFCs, PFCs, and SF6, from 1930 to 2300.

  • Java source code

    Curves

    (All from Oghga Module)

    Colours

    The curve colours depend on the chemical formula of each gas:
  • Blue: Chlorine (Cl) also Bromine (Br).
  • Red: Hydrogen (H)
  • Green: Fluorine (F),
  • Darker: more Carbon (note S counts as 1.5 C)

    So similar gases have similar colours: note the transition from CFCs (blues) to HCFCs (pinks) to HFCs (browns) to PFCs and SF6 (green).

  • EESCL (white) = Effective equivalent stratospheric chlorine. This is used to calculate stratospheric ozone depletion.

    Names

    Common names for the freons use a numeric code:
    CFCxyz or HFCxyz has:
  • x+1 C carbon atoms
  • y-1 H hydrogen atoms
  • z F fluorine atoms
  • 5 +2x -y -z Cl chlorine atoms.
    (note if x=0 it's not shown)

    So, descending the legend, these names are: Sulphur Hexafluoride, Carbon tetrafluoride, C2F6, HFC23, HFC134a, HFC152a, HFC125, HFC32, HFC143a, HFC227ea, HFC245ca, HFC4310mee, HCFC22, HCFC141b, HCFC142b, HCFC123, CH3CCl3, CFC11, CFC12, CFC113, CFC114, CFC115, Carbon Tetrachloride, CF2BrCl, CF3Br, EESCL

    Units

    The menu lets you choose emissions, concentration, or radiative forcing.
  • Emissions are in kilotons (=gigagrams) per year
  • Concentrations are in parts per trillion
  • Radiative Forcing is in milliWatts per m2

    Note these units are 1000 times smaller than on the other gas plot, and 1000,000 times smaller than on the carbon cycle plot. However the warming per molecule is much greater!

    Discussion

    (Note also Oghga Module -how it works)

    Source, lifetime, ozone

    These gases are entirely anthropogenic (except CCl4). They were manufactured specifically because they are inert (unreactive) in the troposphere. The CFCs, HCFCs, HFCs etc. were developed mainly as propellants and refrigerants. SF6 is used mainly during the manufacture of silicon chips.

    However, this inert nature gives them a long lifetime in the atmosphere, allowing enough time to reach the stratosphere where vertical mixing is very slow. There, they are split by intense u.v. radiation, and the chlorine atoms in CFCs and HCFCs are released, catalysing the destruction of the stratospheric ozone layer.

    HCFCs were considered slightly better than CFCs, as the hydrogen atom makes them more vulnerable to reaction in the troposphere, so they have a shorter lifetime and fewer molecules make it to the stratosphere. Nevertheless HCFCs also destroy ozone, and production of both CFCs and HCFCs are now limited by the Montreal protocol.

    The global aeverage radiaive forcing from these gases is partially offset by the reduction of stratospheric ozone, which is also a greenhouse gas. Howevever, beware that the spatial and temporal distributions of these forcings are different (see radiative forcing plot).

    HCFCs are now being replaced by HFCs, which do not destroy ozone but are still powerful greenhouse gases. Some of the SRES scenarios (e.g. A1T) anticipate increasing production of these gases, although they are included in the Kyoto protocol "basket" of greenhouse gases.

    The pure F gases CF4, C2F6 and SF6 (green) are even more inert and have atmospheric lifetimes of thousands of years. CFC12 also has a lifetime of several centuries. You can see this, by switching from emissions to concentration. Emissions of CF4 and SF6 are quite modest, but their concentrations are relatively larger due to accumulation. SF6 also has a particularly high radiative forcing per molecule.

    Changing emissions and lifetime

    The emissions show the transition in manufacture of these gases, from CFCs (blue) to HCFCs (pink) to HFCs (brown).

    For the gases controlled by the Montreal protocol (CFCs, HCFCs), the concentrations are prescribed according to WMO data, the same for all scenarios.

    The emissions of the other gases are dependent on the SRES scenario (SRES menu, top bar). They may also be scaled to the CO2 mitigation, depending on which option you choose from the "other gas" emissions menu (top bar).

    The atmospheric lifetime of each HFCs is also dependent on the concentration of reactive hydroxy radicals (OH), which is itself dependent on the concentration of CO, NOx, VOx and CH4. So adjusting emissions of these gases will also affect HFC concentrations slightly. These atmospheric chemistry interactions are explained in the Oghga Module and "other gas" plot.

    The total radiative forcing from CFCs and HFCs may be seen on "other gas" plot and in the radiative forcing plot (expert level). Note also

  • Comparison with IPCC predictions