Mitigation module

This calculates the global CO2 emissions curve required to stabilise CO2 emissions, CO2 concentration, or global average temperature.
  • Java Source Code

    Interactions

  • Affected by: Kyoto, Carbon, Climate, People
  • Affects: Carbon, Oghga, Regshares, Kyoto,

    Adjustable parameters

  • Mitigation options menu

    Stabilise emissions

  • Stabilisation year and level,
  • Initial growth rate %/yr
  • Quartic formula option and integral

    Stabilise concentration

  • Stabilisation year and level,
  • WRE delayed start option
  • Stabilisation scenario menu

    Stabilise temperature

  • Stabilisation year and level,
  • Iteration or fuzzy-control option
  • Damping option

    Reduce Emissions intensity

  • Reduction %/yr (as this is calculated regionally, may move to regshares)

    How it works

  • See overview of mitigation options for an introduction / discussion.
    Technical explanations of the calculation methods follow below.

    Stabilise CO2 concentration

    Firstly a target concentration curve is set, using the formula defined by the IPCC Technical paper of Enting et al 1994. This is a ratio of two quadratic polynomials, whose constants are defined by
  • initial year concentration (co at to),
  • initial year concn increase (dco/dto),
  • final year concentration (cs at ts),
  • final year stabilisation (dcs/dts=o).
  • initial year d2co/dt2o
    Note, this fifth constraint avoids a kink in the emissions curve, by a method which is more adaptable than the arbitrary parameter described in the Enting paper.

    The emissions are then calculated in each year, by guessing the ocean and biosphere sinks will change as they did in the previous step. The model is then run to calculate the actual sinks and concentration as normal (see carbon module), correcting any deviation from the target in the next step.

    Start/end year, WRE option

    The initial year is usually 2000, or 2013 following Kyoto protocol. However if the WRE "delayed start" option is selected, the initial year = 2002 + (stabilisation level - 350) / 23.0 , and up to that point the curve follows the IS92A "business-as-usual" scenario.

    Note that the original IPCC "S" and "WRE" scenarios both started from 1990, whereas in this model the future starts at 2000. The actual emissions at 2000 are 6.7Gt/yr, slightly higher than the original "S" scenarios at 2000, and slightly lower than projected under the IS92A scenario (7.1Gt/yr). Therefore for the initial phase of WRE scenarios, IS92A has been scaled down to ensure a smooth transition. This initial correction may also have a small impact on the emissions peak.

    The adjustable control or scenario menu defines the final stabilisation level and year. For the scenarios (consistent with IPCC SYR), the final year is 2100 + (level - 450) / 2.

    See also:

  • Carbon cycle plot
  • "different pathways to stabilisation".
  • paper by Wigley Richels & Edmonds, Nature 1995.

    Stabilise temperature

    There are two methods for stabilising temperature:

    Iteration Method

    For a first guess, the radiative forcing is calculated from the required surface temperature increase, ignoring heat exchange with the ocean (as if at equilibrium), and 85% of this forcing is attributed to CO2. This sets a target for CO2 concentration, which is reached using the "stabilise concentration" formula as above. Beyond the stabilisation year, CO2 concentration is fixed by a cubic curve (initially flat, later adjusted to keep the temperature constant). Mitigation is also applied to other gases if specified.

    The whole model calculation then iterates, correcting the CO2 stabilisation target and the endpoint of the cubic curve, until the temperature increase in the stabilisation year and in the final year (2300) are both within 1% of the required stabilisation level, and the temperature change during the final 20 years is also <0.2% of this level.

    Fuzzy control method

    ("expert" level only)
    This method first sets a target temperature curve, according to a formula similar to that used for CO2 stabilisation (note, this target curve is also shown on the temperature plot). The emissions in each year are then adjusted slightly according to the deviation from the target temperature.

    If the other gas emissions are also mitigated proportionally to CO2, oscillations arise due to the "destabilising" effect of sulphate aerosols (on a very short timescale, the sulphate cooling effect is greater than the CO2 warming effect), whereas if these gases are fixed by SRES scenarios, the kinks in the scenarios cause corrective kinks in the CO2. However this formula works well, if the other gas emissions are constant at 2000 levels.

    Stabilise emissions

    This formula simply fixes the global CO2 emissions according to a cubic or quartic curve which is defined by:
  • emissions in the start year (2000 or 2013 after Kyoto)
  • initial growth rate (adjustable parameter, expert level)
  • target level in the stabilisation year (adjustable parameters)
  • flat (rate is zero) in the stabilisation year

    If the quartic curve option is selected (expert level), the integral from 2000-2200 may also be adjusted.

    Land-use change and fossil CO2 emissions

    For all the stabilisation options above, the calculated total CO2 emissions are distributed between fossil fuel and land-use change, using the same constant fractions as in the starting year. This is preferable to fixing land-use CO2 emissions according to SRES, which causes a rather jagged curve for the remaining fossil CO2 emissions. Alternative options may be added later.

    Emissions of other greenhouse gases

    These may also be reduced in proportion to the CO2 mitigation, see
  • Oghga module
  • Other gas emissions