Emissions of other greenhouse gases

Methane (CH4), Nitrous Oxide (N2O), Tropospheric Ozone (O3), HFCs and CFCs are also important greenhouse gases.

So the IPCC SRES scenarios specify emissions of CH4, N2O, HFCs, also of NOx, VOC, and CO which lead to the production of ozone, and of sulphate and carbon aerosols.

To see this, change the SRES scenario from the menu, while watching the curves corresponding to the other greenhouse gases and aerosols. See

  • Other gas plot,
  • F-gas plot
  • Radiative forcing plot.

    Other gas Menu

    Combination with mitigation options

    IPCC also used the SRES projections in combination with CO2 stabilisation scenarios, to derive the emissions and radiative forcing from the other greenhouse gases, in order to calculate the temperature and other climate impacts. Therefore the calculations in Question 6 of the IPCC-TAR Synthesis report assumed that emissions of other gases are fixed according to SRES A1B scenario, for all the CO2 stabilisation levels.

    In this case, the other gases contribute as much to the radiative forcing as 28% extra CO2 (since the CO2 radiative forcing is a logarithmic function of concentration, this applies to any level).

    You can experiment with other assumptions, by choosing an option from the Other Gas menu at the top.

  • (a) SRES fixed (as IPCC SYR)
  • (b) Equal % of SRES as CO2
  • (c) 2000 fixed (constant)
  • (d) Equal % of 2000 as CO2

    The formula for (b) is:

    (Emg,y / Esg,y) = (Emc,y / Esc,y)

    Where: Em=mitigated emissions, Es=SRES emissions
    c = CO2, g = any other gas, y = year

    and the formula for (d) is:

    (Emg,y / Eg,2000) = (Emc,y / Ec,2000)

    Note these formulae apply to emissions of all gases and aerosols, including

  • CH4, N2O
  • CO, NOx, VOC (affect tropospheric Ozone)
  • SOx (=>sulphate aerosol cooling)
  • All HFCs, also SF6, CF4, C2F6 (but not CFCs fixed by Montreal protocol)

    note BC/OC aerosols are either scaled to CO, or to land-use change.

    You can combine these formula with any choice of mitigation option (Stabilise Emissions, Concentration, Temperature) and with any of the SRES scenarios.

    Note that with the IPCC assumption (SRES A1B fixed) 450ppm CO2 corresponds roughly to 550ppm CO2-equivalent (all gases together), leading to a temperature rise of about 2oC (an upper limit proposed by the European Union).

    Whereas if you assume option (b) Equal % of SRES A1B as CO2, you can reach this temperature target stabilising CO2 at about 500ppm.