GCAM customized policies

[rp9823]

I have 3 questions:

1. Is there any available guide on how to set up a customized policy on GCAM?
2. If i want to run a scenario with one of the "pre - defined" policies, e.g. carbon_tax_10_5, should I add the policy to the scenario components in the configuration_ref file or in the configuration_policy? because I noticed they're slightly different.
3. If I set a scenario by fixing the emission pathway and solving for carbon price, should I enable the target finder mode?
   Thanks

[Goldfish63]

Hi, Thanks for your questions. I also encountered similar issues you posted before and I would like to share my views.

1. The gcam-training offers some learning materials and some examples for you to grasp quickly. This tutorial provides some insights on how to design a policy scenario. Also, you can follow the examples on this website.
   

https://jgcri.github.io/gcam_training/gcam.html#Scenario_Adjustments

2. You should add the policy (e.g. carbon_tax_10_5) in the configuration_policy file. Configuration_ref file defines the reference scenario for GCAM release.

3. I think the find-path mode should be set to 1. This issue also mention the similar problem.Issue with keeping carbon tax fixed #238

I am also quite new to gcam. Please correct if there are errors. Thanks again.

[pkyle]

Just to add to that, if I'm running a simple carbon price or emissions constraint scenario, I usually start from configuration_ref.xml, leave find-path set to 0, and add the carbon price or emissions constraint file to the scenarioComponents.
find-path set to 1 (as in configuration_policy.xml) indicates to use target-finder mode, which is used for solving a policy that will require multiple iterations of the model itself. For example, if you wanted to hit an end of century radiative forcing target, the exact concentrations of each gas in 2100 aren't known, as a number of different levels of each gas could work. Moreover, the emissions pathways of each gas similarly are not known a priori. For such a policy design, the model will have to run a number of different times, adjusting the GHG price trajectory such that the end of century target is met. In this mode, only the final scenario run is saved and written to the output database.