Earth Energy Budget Calculator

EEBC is a simple spreadsheet for calculating the Earth's energy budget. It can be found here.

The spreadsheet takes as input, several global averages extracted from satellite data and from atmospheric absorption simulations. Using equations based on the radiative model used to interpret satellite data, 3 power fluxes are calculated using 2 different methods, one representing the source of the power and the other representing the sink, both of which much be equal over the long term. The 3 computed variables are the output power (255K equiv), the surface power (surf temp equiv) and cloud power (cloud temp equiv). The results of the 2 methods are compared to each other and the error is reported in red.

The source method uses measured average temperatures whose results are reported in magenta. The sink method calculates where the sourced power is coming from and is reported in black. All of the results, including the error values, are in blue shaded fields. In addition, the equivalent temperature of the output power is also computed.

Any of the inputs may be changed and the results will be recalculated. The equations buried in the spreadsheet have been partitioned into small, easy to understand, pieces. Other than physical constants and indicated inputs, everything else is calculated. Feel free to make a copy of the spreadsheet and add to or modify the equations.

The goal of tweaking variables, dials and even equations would be to minimize the total error, where the error for each power flux calculation is the percentage difference between the source and sink calculations. The only tweaking done to produce the default results was a minor (few tenths of a degree K) change in the cloud bottom temperature, although this variable has a high uncertainty and the tweak was well within the uncertainty limits.

There are several color coded groups of fields. The orange fields labeled "Satellite Data" are inputs derived from the 25 year averages calculated from weather satellite radiances. Most of these are known to be relatively accurate and probably don't want to be changed. The total rainfall has the most uncertainty. The cloud bottom temperature is estimated based on the average lapse rate and cloud deck heights and also has a relatively high uncertainty.

The green fields labeled "Atmospheric Absorption" are values representing the fraction of the radiated energy captured by GHG, as calculated using average water, CO2 and ozone concentrations. If you don't trust the method used to obtain these from HITRAN 2008 absorption line data and satellite reported GHG concentrations, they can be adjusted. For reference purposes, the methods also indicate that doubling CO2 will increase the total surface to space and cloud to space absorption by about 1%, for example from 57% to 58%. The general formula is to split absorbed energy between up and down where a dial can adjust the ratio, and which defaults to an even split.

The blue fields are the "Dials". The 'absorb down' dial is nominally 0.5 and represents the fraction of the absorbed GHG power that is recirculated towards the surface, where the remaining power leaves the planet. The 'latent delta' is an amount of energy that can be added (or subtracted) from the latent heat of evaporation for water. This can be used to tune the latent heat term and can be offset with the recommended value of global annual precipitation. The 'absorb split' field will offer suggestions for replacement surface to space and surface to cloud absorption values based on a selected bias.

The fields with a bright yellow background are the ones most likely to need adjustment. The fields with a light yellow background may be changed, but their values are well known and changes are not recommended.

All of the input and primary output fields have a note attached to them which explains their purpose. Set the mouse pointer over the field you want more information about.