Wednesday, September 9, 2009

2 box model

Yet another 2 box climate model. Excel file model available here:

Click the image to see graph detail.

Since my model uses a different technique than some recently discussed fitting models, not all parameters may correspond, but this is what I use for heat capacities:
Co=400 MJ/(K-m^2) Heat capacity of ocean box (~100m well mixed depth)
Ca= 50 MJ/(K-m^2) (Comparable to Cs?) Heat capacity of atmosphere box (~3x higher than dry air, due to heat required to maintain constant RH?).

Most of the other fitting parameters are the heat conductivities between the boxes and outside (in W/(K-m^2)):
Gao = 3.0 atmosphere to ocean
Godo=0.22 ocean to deep ocean
Gsa =1.78 space to atmosphere (this corresponds to 2.25K climate sensitivity if CO2 doubling causes 4 W/m^2 forcing).

Other assumptions are:
Both space and deep ocean are heat sinks at -0.1 K from the GISS baseline
All forcing is applied to the atmosphere box.
The temperature to compare to GISS land-ocean data is a weighted average (Ta+2To)/3 based on area.

There are some additional comments in the spreadsheet itself.

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