This is part of the labels / documentation for <a href='http://jcm.chooseclimate.org'>Java Climate Model</a><hr/>

#oghga		§This module handles the emissions, atmospheric chemistry and radiative forcing for all gases except CO2
  £§iobinfo ££oghgahowwork ££oghgafuture

#othgasplot		§£^apptag This shows the emissions, concentration or radiative forcing of CH4, N2O, and tropospheric Ozone (from emissions of CO, NOx, VOCs). Also incldued are emissions of SOx, and radiative forcing of F-gases and stratospheric ozone.

The emissions are prescribed by SRES scenarios, optionally mitigated proportionally to CO2 -see @othgasemit.

These gases are removed from the atmosphere mainly by oxidation. Their lifetimes vary widely and are affected by feedbacks involving OH radicals - see @atchem.
  £^interacs £^curves
  ²°adju The "other gas" curve in @radforplot shows the total forcing from all these greenhouse gases (excluding the aerosols). The @fgasplot shows the details of HFCs and CFCs. ²
  £^scales
  ²Note: Emissions and concentrations units are 1000 times smaller than for CO2, but the warming effect per molecule is much greater.²
  £^controls £^menopts ££atchem

#othgasemit		§See the links above for the formula for each variant.
  These formulae scale the emissions of all gases other than CO2, including CH4, N2O, HFCs, PFCs,   SF6,  tropospheric ozone precursors (CO,VOC,NOx) and aerosols (SOx, Soot). Only the gases already controlled by the Montreal protocol (ClFCs, HClFCs) are excluded.
  ²°cogs Note: BC/OC aerosols are either scaled to CO, or to land-use change.  -see @radforaerosol ²
  <hr>The chosen formula apply to <b>all</b> stabilisation scenarios in JCM
  ²(see @stabemitdoc, @stabconcdoc, @stabrfdoc, @stabtempdoc, @stabseadoc)²

@sresscale is the default option for all JCM stabilisation scenarios.
  @sresfix (with scenario @A1B) was used in IPCC-SYR (see @ipccothgas)
  <hr>See also @othgasplot, @fgasplot, @radforplot

#sresfix		§This option simply sets the other gas emissions according to the no-policy SRES scenario chosen from @sresmenu, with no mitigation. This is the option used in IPCCTAR-SYR (see @ipccothgas).

#sresscale		§This option reduces the emissions of all gases in the same proportion, compared to a baseline SRES scenario  (choose from @sresmenu). The formula is:

(Em<sub>g,y</sub> / Es<sub>g,y</sub>) = (Em<sub>c,y</sub> / Es<sub>c,y</sub>)

Where: Em=mitigated emissions, Es=SRES emissions

c = CO2, g = any other gas, y = year

#2000fix		§Other gas emissions set at 2000 level ? useful for comparing the effect of their different lifetimes (@othgasplot, @fgasplot)

#2000scale		§This option reduces the emissions of all gases in the same proportion, compared to their 2000 level. The formula is:

(Em<sub>g,y</sub> / E<sub>g,2000</sub>) = (Em<sub>c,y</sub> / E<sub>c,2000</sub>)

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

#OHef		§See @atchem. (note, when this is disabled, the historical concentrations are not consistent with measurements)

#tarO3		§The original formula for calculating tropospheric ozone in IPCC TAR was corrected (by the same authors) to be more consistent with historical concentrations. Select this option for reproducing IPCC datatables made using the old formulae. - see @compareipcc

#oghgahowwork		§The formulae are identical to those used in the Bern CC Model, which was used to calculate the data given in IPCC-TAR-WG1 Ch6 and SRES appendix. The full set of equations are given in the appendix of Joos et al 2001 (@references).

The atmospheric chemistry formulae (See @atchem) are derived from the IPCC workshop of Prather et al. These include a simple parameterisation to calculate O3 and OH from CH4, NOx, CO and VOC, and the effect of OH on the lifetime of CH4 and of all the HFCs. The effect of N2O on it's own lifetime is also considered. The radiative forcing calculation includes the spectral overlap between CH4 and N2O.

The concentrations of the Montreal gases (CFCs, HCFCs) are prescribed by WMO data, and emissions are estimated by an inverse method.  See @fgases

For speed, the F-gas concentrations and radiative forcing are calculated using a ramp function over five year intervals, since the original emissions data is also in five-year intervals.

@othgasemit explains the formulae for scaling other gas emissions for mitigation scenarios. Note also @ipccothgas.

#atchem		§The gases shown in the @othgasplot panel (calculated in @oghga module) are destroyed by chemical oxidation in the atmosphere, unlike CO2 which is absorbed into the ocean and biosphere sinks (see @carbonstoreplot).

Their atmospheric lifetimes vary widely. Tropospheric Ozone survives only a few days in the atmosphere, the lifetime of CH4 is just under a decade (depending on OH, see below), whilst the lifetime of N2O is just over a century (similar to CO2).
  ³CO, NOx, VOC, Ozone and Hydroxyl radicals³
  ² °adju Choosing "2000 fixed" from the @othgasemit shows the effect of different lifetimes (CH4 and ozone concentrations level off rapidly, N2O much more slowly). ²

Carbon Monoxide (CO) and Volatile Organic Carbons (VOC) are produced mainly by incomplete fossil fuel combustion (e.g. in cool engines or with insufficent oxygen), whilst NOx is produced mainly by the reaction of atmospheric nitrogen and oxygen in very hot engines. These gases have no direct influence on radiative forcing, but contribute to the formation of tropospheric ozone (O3), which is the an important greenhouse gas, the next after methane.

Note that we need ozone in the stratosphere where it protects us from ultraviolet radiation, but not so much in the troposphere where it causes adverse health impacts and photochemical smog.

CO, NOx, VOC and CH4 also affect the production of reactive hydroxy radicals (OH). These play a major role in atmospheric chemistry, including the oxidation of CH4 and the HFCs. Consequently CH4 has an effect on its own lifetime.

The atmospheric chemistry leading to formation and destruction of O3 and OH is very complicated, with dozens of transient species and reactions which are difficult to measure. The distribution of these gases is also highly variable over space and time. So this model uses some simple formulae taken from an IPCC workshop (Prather et al) (see @oghga module). Note that these may not be valid beyond the range of SRES scenarios for which they were calibrated.
  ³Minor radiative forcing effects³
  The model also accounts for the overlap in the radiative forcing of CH4 and N2O, and the small cooling effect of water vapour produced by the oxidation of methane in the stratosphere.
  ³Atmospheric Aerosols³
  The @othgasplot panel also shows Sulphate emissions (SOx), which lead to the production of sulphate aerosols -see @radforaerosol, @radforplot

Black carbon and organic carbon aerosols may also be calculated as a function of CO emissions (@oghga).

The oghga module predictions may be checked against data from IPCCTAR-WG1-SRESappx. See @radforplot, @compareipcc, note @tarO3 option.

#oghgafuture	¨fut		§<li>There could be strong biogeochemical climate feedback processes affecting natural methane emissions, for example the effect of melting Siberian permafrost. A simple way to explore this uncertainty should be added.  <li>Anthropogenic emissions of CH4 and N2O are mainly due to land-use factors, and this should be illustrated in the model.  <li>A related task is to incoporate emissions abatement cost functions for each gas, for use with mitigation scenarios, to replace simple scaling to SRES.  <li>There is also a large natural source of sulphate aerosols from marine phytoplankton, which may change as a function of ocean circulation. Although the potential feedback is poorly quantified, it should not be ignored.

#cfc		§see @fgasplot for details

#hfc		§see @fgasplot for details