Modify the yield in AgProductChange.

[tutututuni]

In GCAM, the yield results can be modified by adjusting the coefficients in AgProductChange. How is this specifically operated? It seems that the yield is calculated based on the baseline annual yield, regional coefficients, and yield growth rate. Where is the formula for calculating the yield using these three parameters presented?

[pkyle]

AgProdChange is the annual rate of yield change in the years from the prior to the current timestep. It is used in all "future" model time periods, 2020-2100. The model's time periods are all 5-year timesteps which simplified the equation below somewhat:

Yield(t) = Yield(t-1) * (1 + AgProdChange)^TimestepLength

Note that this parameter only applies to the yield, typically indicated in kg of crop per m2 of land area. It does not apply to any other modeled inputs (fertilizer, water), whose coefficients are specified in each time period.