Parameters for tuning a simple climate model (plus aerosol forcing)
Jason Lowe (Met Office, Hadley Centre for Climate Prediction and Research, UK) has provided some tuning data from HadCM3 for the first phase of the study, and aerosol forcing for the second. Parameters for a simple double exponential impulse response function model are given below. Parties do not have to use the IRF model if they have an alternative.
|Impulse response climate model|
A two box linear model has been fitted to the HadCM3 4xCO2 run f or both global mean temperature (T) and thermal expansion (S) response. The data can be viewed from the links below. The equations and parameters are as follows:
Where T(t) is the transient global mean surface temperature change at time t, F(t) is the relative radiative forcing (expressed as a fraction of the equilibrium value) and R(t) is the climate response function. A similar expression can be written for sea level.
Note:- The forcing caused by a doubling of CO2 quoted in the IPCC TAR (page 358) is 3.71 Wm-2. The value estimated for CO2 doubling in HadCM3 is 3.74 Wm-2. The constants are given below.
The constants a1, a2, t1,t2 and Tfinal etc. were derived by fitting the temperature curve to a GCM stabilisation experiment in which the carbon dioxide was modified. The carbon dioxide concentration was increased from a pre-industrial value at 2% per year compounded until it reached 4 times the pre-industrial level. It was stabilised at this level for the remainder of the simulation.
|A2 OAGCM simulation|
|This experiment used the HadCM3 model to simulate the climate between 1860 and 2100. Prior to 1990 historical concentrations, derived from historical emissions, were used. Beyond 1990 the concentrations were derived from the A2 emissions scenarios. The simulation included the following chemical species:
CO2, CH4, N2O, CFC-11, CFC-12, CFC-113,
Details of the experiment can be found in the Hadley Centre technical note
Notes on forcing:
Note: In the current work we are only planning to include the first three greenhouse gases and sulphate aerosol. There will be some differences between the results obtained using the simple parameterisations and the OAGCM (HadCM3) because:
|Downloadable datasets and figures|
|- Download the TXT f
- Download the PS files for viewing in eg. GhostView
- Click on the GIFs to view diagrams directly
* sea-level time-series 4xCO2_sl was originally incorrect. Updated May 14th. If you previously downloaded it, please collect it again.