Incorporate an additional constraint on peak temperature targets

[yanxzh]

Hi,

I have been trying to incorporate an additional constraint on peak temperature targets into the source code of GCAM, by imposing penalties for deviations from the temperature target. However, after multiple iterations, the model fails to simultaneously satisfy both the original end goals and this new constraint. I suspect this may be due to the solver prioritizing the end target (which differs from the logic of conventional optimization) and am wondering:

1. Whether it is feasible to implement such a constraint within GCAM;
2. If feasible, what adjustments are needed to achieve simultaneous satisfaction of both the end goals and the new constraint.

The attachments are my adjustments in temperature_target.cpp and policy_target_runner.cpp.

Thank you very much for your assistance!

policy_target_runner.cpp
temperature_target.cpp

[ouyang363]

Dear Xizhe

As for as I know there's no such option. But basically the year of peak warming is the year of reaching net-zero globally. So you can set different net-zero years with different trajectories: the earlier you start to decline emissions and reach net-zero, the lower peak warming you would have; also, if there's no post-peaking climate targets, the model could have infinite numbers of options after peaking (and then the model doesn't know how to deal with this).

Another option is looking at different AR6 warming-categories (C1, C2 etc), check their carbon budgets and key indicators, and use those as proxy settings in your emissions constraints.

Happy to further discuss this via Wechat (ouyang363)

[yanxzh]

Thank you so much! I really appreciate your advice, and it’s a pleasure discussing this with you.